Configuring AAA Services

This module describes the implementation of the administrative model of task-based authorization used to control user access in the software system. The major tasks required to implement task-based authorization involve configuring user groups and task groups.

User groups and task groups are configured through the software command set used for authentication, authorization and accounting (AAA) services. Authentication commands are used to verify the identity of a user or principal. Authorization commands are used to verify that an authenticated user (or principal) is granted permission to perform a specific task. Accounting commands are used for logging of sessions and to create an audit trail by recording certain user- or system-generated actions.

AAA is part of the software base package and is available by default.

Prerequisites for Configuring AAA Services

The following are the prerequisites to configure AAA services:

  • You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

  • Establish a root system user using the initial setup dialog. The administrator may configure a few local users without any specific AAA configuration. The external security server becomes necessary when user accounts are shared among many routers within an administrative domain. A typical configuration would include the use of an external AAA security server and database with the local database option as a backup in case the external server becomes unreachable.

Restrictions for Configuring AAA Services

This section lists the restrictions for configuring AAA services.

Compatibility

Compatibility is verified with the Cisco freeware TACACS+ server and FreeRADIUS only.

Interoperability

Router administrators can use the same AAA server software and database (for example, CiscoSecure ACS) for the router and any other Cisco equipment that does not currently run the Cisco software. To support interoperability between the router and external TACACS+ servers that do not support task IDs, see the “Task IDs for TACACS+ and RADIUS Authenticated Users” section.

Configure Task group

Task-based authorization employs the concept of a task ID as its basic element. A task ID defines the permission to execute an operation for a given user. Each user is associated with a set of permitted router operation tasks identified by task IDs. Users are granted authority by being assigned to user groups that are in turn associated with task groups. Each task group is associated with one or more task IDs. The first configuration task in setting up an authorization scheme to configure the task groups, followed by user groups, followed by individual users.

Specific task IDs can be removed from a task group by specifying the no prefix for the task command.

The task group itself can be removed. Deleting a task group that is still referred to elsewhere results in an error.

Before you begin

Before creating task groups and associating them with task IDs, you should have some familiarity with the router list of task IDs and the purpose of each task ID. Use the show aaa task supported command to display a complete list of task IDs.


Note

Only users with write permissions for the AAA task ID can configure task groups.

SUMMARY STEPS

  1. configure
  2. taskgroup taskgroup-name
  3. description string
  4. task {read | write | execute | debug} taskid-name
  5. Repeat for each task ID to be associated with the task group named in Step 2.
  6. commit

DETAILED STEPS

Step 1

configure

Step 2

taskgroup taskgroup-name

Example:


RP/0/RP0/CPU0:router(config)# taskgroup beta

Creates a name for a particular task group and enters task group configuration submode.

  • Specific task groups can be removed from the system by specifying the no form of the taskgroup command.

Step 3

description string

Example:


RP/0/RP0/CPU0:router(config-tg)# description this is a sample task group description

(Optional) Creates a description of the task group named in Step 2.

Step 4

task {read | write | execute | debug} taskid-name

Example:


RP/0/RP0/CPU0:router(config-tg)# task read bgp

Specifies a task ID to be associated with the task group named in Step 2.

  • Assigns read permission for any CLI or API invocations associated with that task ID and performed by a member of the task group.

  • Specific task IDs can be removed from a task group by specifying the no prefix for the task command.

Step 5

Repeat for each task ID to be associated with the task group named in Step 2.

—
Step 6

commit

What to do next

After completing configuration of a full set of task groups, configure a full set of user groups as described in the Configuring User Groups section.

Configure User Groups

User groups are configured with the command parameters for a set of users, such as task groups. Entering the usergroup command accesses the user group configuration submode. Users can remove specific user groups by using the no form of the usergroup command. Deleting a usergroup that is still referenced in the system results in a warning.

Before you begin


Note

Only users associated with the WRITE:AAA task ID can configure user groups. User groups cannot inherit properties from predefined groups, such as owner-sdr.

SUMMARY STEPS

  1. configure
  2. usergroup usergroup-name
  3. description string
  4. inherit usergroup usergroup-name
  5. taskgroup taskgroup-name
  6. Repeat Step for each task group to be associated with the user group named in Step 2.
  7. commit

DETAILED STEPS

Step 1

configure

Step 2

usergroup usergroup-name

Example:

 RP/0/RP0/CPU0:router(config)# usergroup beta

Creates a name for a particular user group and enters user group configuration submode.

  • Specific user groups can be removed from the system by specifying the no form of the usergroup command.

Step 3

description string

Example:

 RP/0/RP0/CPU0:router(config-ug)# 
description this is a sample user group description

(Optional) Creates a description of the user group named in Step 2.

Step 4

inherit usergroup usergroup-name

Example:

 RP/0/RP0/CPU0:router(config-ug)# 
inherit usergroup sales

  • Explicitly defines permissions for the user group.

Step 5

taskgroup taskgroup-name

Example:

 RP/0/RP0/CPU0:router(config-ug)# taskgroup beta

Associates the user group named in Step 2 with the task group named in this step.

  • The user group takes on the configuration attributes (task ID list and permissions) already defined for the entered task group.

Step 6

Repeat Step for each task group to be associated with the user group named in Step 2.

—
Step 7

commit

Configure Users

Perform this task to configure a user.

Each user is identified by a username that is unique across the administrative domain. Each user should be made a member of at least one user group. Deleting a user group may orphan the users associated with that group. The AAA server authenticates orphaned users but most commands are not authorized.

SUMMARY STEPS

  1. configure
  2. username user-name
  3. Do one of the following:
    • password {0 | 7} password
    • secret {0 | 5} secret
  4. group group-name
  5. Repeat step 4 for each user group to be associated with the user specified in step 2.
  6. commit

DETAILED STEPS

Step 1

configure

Step 2

username user-name

Example:

 RP/0/RP0/CPU0:router(config)# username user1

Creates a name for a new user (or identifies a current user) and enters username configuration submode.

  • The user-name argument can be only one word. Spaces and quotation marks are not allowed.

Step 3

Do one of the following:

  • password {0 | 7} password
  • secret {0 | 5} secret

Example:

 RP/0/RP0/CPU0:router(config-un)# password 0 pwd1

or 

 RP/0/RP0/CPU0:router(config-un)# secret 0 sec1

Specifies a password for the user named in step 2.

  • Use the secret command to create a secure login password for the user names specified in step 2.

  • Entering 0 following the password command specifies that an unencrypted (clear-text) password follows. Entering 7 following the password command specifies that an encrypted password follows.

  • Entering 0 following the secret command specifies that a secure unencrypted (clear-text) password follows. Entering 5 following the secret command specifies that a secure encrypted password follows.

  • Type 0 is the default for the password and secret commands.

Step 4

group group-name

Example:

 RP/0/RP0/CPU0:router(config-un)# group sysadmin

Assigns the user named in step 2 to a user group that has already been defined through the usergroup command.

  • The user takes on all attributes of the user group, as defined by that user group’s association to various task groups.

  • Each user must be assigned to at least one user group. A user may belong to multiple user groups.

Step 5

Repeat step 4 for each user group to be associated with the user specified in step 2.

—
Step 6

commit

Configure Router to RADIUS Server Communication

This task configures router to RADIUS server communication. The RADIUS host is normally a multiuser system running RADIUS server software from Cisco (CiscoSecure ACS), Livingston, Merit, Microsoft, or another software provider. Configuring router to RADIUS server communication can have several components:

  • Hostname or IP address

  • Authentication destination port

  • Accounting destination port

  • Retransmission value

  • Timeout period

  • Key string

RADIUS security servers are identified on the basis of their hostname or IP address, hostname and specific User Datagram Protocol (UDP) port numbers, or IP address and specific UDP port numbers. The combination of the IP address and UDP port numbers creates a unique identifier, allowing different ports to be individually defined as RADIUS hosts providing a specific AAA service. In other words, this unique identifier enables RADIUS requests to be sent to multiple UDP ports on a server at the same IP address. If two different host entries on the same RADIUS server are configured for the same service—for example, accounting—the second host entry configured acts as an automatic switchover backup to the first one. Using this example, if the first host entry fails to provide accounting services, the network access server tries the second host entry configured on the same device for accounting services. (The RADIUS host entries are tried in the order they are configured.)

A RADIUS server and a Cisco router use a shared secret text string to encrypt passwords and exchange responses.To configure RADIUS to use the AAA security commands, you must specify the host running the RADIUS server daemon and a secret text (key) string that it shares with the router.

The timeout, retransmission, and encryption key values are configurable globally for all RADIUS servers, on a per-server basis, or in some combination of global and per-server settings. To apply these settings globally to all RADIUS servers communicating with the router, use the three unique global commands: radius-server timeout, radius-server retransmit, and radius-server key. To apply these values on a specific RADIUS server, use the radius-server host command.


Note

You can configure both global and per-server timeout, retransmission, and key value commands simultaneously on the same Cisco network access server. If both global and per-server functions are configured on a router, the per-server timer, retransmission, and key value commands override global timer, retransmission, and key value commands.

SUMMARY STEPS

  1. configure
  2. radius-server host {hostname | ip-address} [auth-port port-number] [acct-port port-number] [timeout seconds] [retransmit retries] [key string]
  3. radius-server retransmit retries
  4. radius-server timeout seconds
  5. radius-server key {0 clear-text-key | 7 encrypted-key | clear-text-key}
  6. radius source-interface type instance [vrf vrf-id]
  7. Repeat step 2 through step 6 for each external server to be configured.
  8. commit
  9. show radius

DETAILED STEPS

Step 1

configure

Step 2

radius-server host {hostname | ip-address} [auth-port port-number] [acct-port port-number] [timeout seconds] [retransmit retries] [key string]

Example:

 RP/0//CPU0:router(config)# radius-server host host1

Specifies the hostname or IP address of the remote RADIUS server host.

  • Use the auth-port port-number option to configure a specific UDP port on this RADIUS server to be used solely for authentication.

  • Use the acct-port port-number option to configure a specific UDP port on this RADIUS server to be used solely for accounting.

  • To configure the network access server to recognize more than one host entry associated with a single IP address, simply repeat this command as many times as necessary, making sure that each UDP port number is different. Set the timeout, retransmit, and encryption key values to use with the specific RADIUS host.

  • If no timeout is set, the global value is used; otherwise, enter a value in the range 1 to 1000. If no retransmit value is set, the global value is used; otherwise enter a value in the range 1 to 100. If no key string is specified, the global value is used.

Note 

The key is a text string that must match the encryption key used on the RADIUS server. Always configure the key as the last item in the radius-server host command syntax because the leading spaces are ignored, but spaces within and at the end of the key are used. If you use spaces in your key, do not enclose the key in quotation marks unless the quotation marks themselves are part of the key.

Step 3

radius-server retransmit retries

Example:

 RP/0/RP0/CPU0:router(config)# radius-server retransmit 5

Specifies the number of times the software searches the list of RADIUS server hosts before giving up.

  • In the example, the number of retransmission attempts is set to 5.

Step 4

radius-server timeout seconds

Example:

 RP/0/RP0/CPU0:router(config)# radius-server timeout 10

Sets the number of seconds a router waits for a server host to reply before timing out.

  • In the example, the interval timer is set to 10 seconds.

Step 5

radius-server key {0 clear-text-key | 7 encrypted-key | clear-text-key}

Example:

 RP/0/RP0/CPU0:router(config)# radius-server key 0 samplekey

Sets the authentication and encryption key for all RADIUS communications between the router and the RADIUS daemon.

Step 6

radius source-interface type instance [vrf vrf-id]

Example:

 RP/0/RP0/CPU0:router(config)# radius source-interface 0/3/0/1

(Optional) Forces RADIUS to use the IP address of a specified interface or subinterface for all outgoing RADIUS packets.

  • The specified interface or subinterface must have an IP address associated with it. If the specified interface or subinterface does not have an IP address or is in the down state, then RADIUS reverts to the default. To avoid this, add an IP address to the interface or subinterface or bring the interface to the up state.

The vrf keyword enables the specification on a per-VRF basis.

Step 7

Repeat step 2 through step 6 for each external server to be configured.

—
Step 8

commit

Step 9

show radius

Example:

 RP/0/RP0/CPU0:router# show radius

(Optional) Displays information about the RADIUS servers that are configured in the system.

Radius Summary Example 



radius source-interface Mgm0/rp0/cpu0/0 vrf default
radius-server timeout 10
radius-server retransmit 2
!
! OOB RADIUS
radius-server host 123.100.100.186 auth-port 1812 acct-port 1813
key cisco123
timeout 10
retransmit 2
!
radius-server host 123.100.100.187 auth-port 1812 acct-port 1813
key cisco123
timeout 10
retransmit 2
!
aaa group server radius radgrp
server 123.100.100.186 auth-port 1812 acct-port 1813
server 123.100.100.187 auth-port 1812 acct-port 1813
!
aaa authorization exec radauthen group radgrp local
aaa authentication login radlogin group radgrp local
!
line template vty
authorization exec radauthen
login authentication radlogin
timestamp disable
exec-timeout 0 0
!
vty-pool default 0 99 line-template vty

Configure RADIUS Dead-Server Detection

The RADIUS Dead-Server Detection feature lets you configure and determine the criteria that is used to mark a RADIUS server as dead. If no criteria is explicitly configured, the criteria is computed dynamically on the basis of the number of outstanding transactions. The RADIUS dead-server detection configuration results in the prompt detection of RADIUS servers that have stopped responding. The prompt detection of nonresponding RADIUS servers and the avoidance of swamped and dead-to-live-to-dead-again servers result in less deadtime and quicker packet processing.

You can configure the minimum amount of time, in seconds, that must elapse from the time that the router last received a valid packet from the RADIUS server to the time the server is marked as dead. If a packet has not been received since the router booted, and there is a timeout, the time criterion is treated as though it was met.

In addition, you can configure the number of consecutive timeouts that must occur on the router before the RADIUS server is marked as dead. If the server performs both authentication and accounting, both types of packets are included in the number. Improperly constructed packets are counted as though they are timeouts. Only retransmissions are counted, not the initial transmission. For example, each timeout causes one retransmission to be sent.


Note

Both the time criterion and the tries criterion must be met for the server to be marked as dead.

The radius-server deadtime command specifies the time, in minutes, for which a server is marked as dead, remains dead, and, after this period, is marked alive even when no responses were received from it. When the dead criteria are configured, the servers are not monitored unless the radius-server deadtime command is configured

SUMMARY STEPS

  1. configure
  2. radius-server deadtime minutes
  3. radius-server dead-criteria time seconds
  4. radius-server dead-criteria tries tries
  5. commit
  6. show radius dead-criteria host ip-addr [auth-port auth-port] [acct-port acct-port]

DETAILED STEPS

Step 1

configure

Step 2

radius-server deadtime minutes

Example:


RP/0/RP0/CPU0:router(config)# radius-server deadtime 5

Improves RADIUS response times when some servers might be unavailable and causes the unavailable servers to be skipped immediately.

Step 3

radius-server dead-criteria time seconds

Example:


RP/0/RP0/CPU0:router(config)# radius-server dead-criteria time 5

Establishes the time for the dead-criteria conditions for a RADIUS server to be marked as dead.

Step 4

radius-server dead-criteria tries tries

Example:


RP/0/RP0/CPU0:router(config)# radius-server dead-criteria tries 4

Establishes the number of tries for the dead-criteria conditions for a RADIUS server to be marked as dead.

Step 5

commit

Step 6

show radius dead-criteria host ip-addr [auth-port auth-port] [acct-port acct-port]

Example:


RP/0/RP0/CPU0:router# show radius dead-criteria host 172.19.192.80

(Optional) Displays dead-server-detection information that has been requested for a RADIUS server at the specified IP address.

Configure TACACS+ Server

This task configures a TACACS+ server.

The port, if not specified, defaults to the standard port number, 49. The timeout and key parameters can be specified globally for all TACACS+ servers. The timeout parameter specifies how long the AAA server waits to receive a response from the TACACS+ server. The key parameter specifies an authentication and encryption key shared between the AAA server and the TACACS+ server.

SUMMARY STEPS

  1. configure
  2. tacacs-server host host-name port port-number
  3. tacacs-server host host-name timeout seconds
  4. tacacs-server host host-name key [0 | 7] auth-key
  5. tacacs-server host host-name single-connection
  6. tacacs source-interface type instance
  7. Repeat step 2 through step 5 for each external server to be configured.
  8. commit
  9. show tacacs

DETAILED STEPS

Step 1

configure

Step 2

tacacs-server host host-name port port-number

Example:


RP/0/RP0/CPU0:router(config)# tacacs-server host 209.165.200.226 port 51 
RP/0/RP0/CPU0:router(config-tacacs-host)#

Specifies a TACACS+ host server and optionally specifies a server port number.

  • This option overrides the default, port 49. Valid port numbers range from 1 to 65535.

Step 3

tacacs-server host host-name timeout seconds

Example:


RP/0/RP0/CPU0:router(config-tacacs-host)# tacacs-server host 209.165.200.226 timeout 30 
RP/0/RP0/CPU0:router(config)#

Specifies a TACACS+ host server and optionally specifies a timeout value that sets the length of time the AAA server waits to receive a response from the TACACS+ server.

  • This option overrides the global timeout value set with the tacacs-server timeout command for only this server. The timeout value is expressed as an integer in terms of timeout interval seconds. The range is from 1 to 1000.

Step 4

tacacs-server host host-name key [0 | 7] auth-key

Example:

RP/0/RP0/CPU0:router(config)# tacacs-server host 209.165.200.226 key 0 a_secret

Specifies a TACACS+ host server and optionally specifies an authentication and encryption key shared between the AAA server and the TACACS+ server.

  • The TACACS+ packets are encrypted using this key. This key must match the key used by TACACS+ daemon. Specifying this key overrides the global key set by the tacacs-server key command for only this server.

  • (Optional) Entering 0 indicates that an unencrypted (clear-text) key follows.

  • (Optional) Entering 7 indicates that an encrypted key follows.

  • The auth-key argument specifies the encrypted or unencrypted key to be shared between the AAA server and the TACACS+ server.

Step 5

tacacs-server host host-name single-connection

Example:

RP/0/RP0/CPU0:router(config)# tacacs-server host 209.165.200.226 single-connection

Prompts the router to multiplex all TACACS+ requests to this server over a single TCP connection. By default, a separate connection is used for each session.

Step 6

tacacs source-interface type instance

Example:

RP/0/RP0/CPU0:router(config)# tacacs source-interface 0/4/0/0

(Optional) Specifies the source IP address of a selected interface for all outgoing TACACS+ packets.

  • The specified interface or subinterface must have an IP address associated with it. If the specified interface or subinterface does not have an IP address or is in the down state, then TACACS+ reverts to the default interface. To avoid this, add an IP address to the interface or subinterface or bring the interface to the up state.

  • The vrf option specifies the Virtual Private Network (VPN) routing and forwarding (VRF) reference of an AAA TACACS+ server group.

Step 7

Repeat step 2 through step 5 for each external server to be configured.

—
Step 8

commit

Step 9

show tacacs

Example:

RP/0/RP0/CPU0:router# show tacacs

(Optional) Displays information about the TACACS+ servers that are configured in the system.

Tacacs Summary Example: 



! OOB TAC
tacacs-server host 123.100.100.186 port 49
key lm51
!
tacacs-server host 123.100.100.187 port 49
key lm51
!
aaa group server tacacs+ tacgrp
server 123.100.100.186
server 123.100.100.187
!
aaa group server tacacs+ eem
server 123.100.100.186
server 123.100.100.187
!
aaa authorization exec tacauthen group tacgrp local
aaa authentication login taclogin group tacgrp local
!
line console
authorization exec tacauthen
login authentication taclogin
timeout login response 30
timestamp
exec-timeout 0 0
session-timeout 15
!
vty-pool default 0 99 line-template console

Configure RADIUS Server Groups

This task configures RADIUS server groups.

The user can enter one or more server commands. The server command specifies the hostname or IP address of an external RADIUS server along with port numbers. When configured, this server group can be referenced from the AAA method lists (used while configuring authentication, authorization, or accounting).

Before you begin

For configuration to succeed, the external server should be accessible at the time of configuration.

SUMMARY STEPS

  1. configure
  2. aaa group server radius group-name
  3. server {hostname | ip-address} [auth-port port-number] [acct-port port-number]
  4. Repeat step 4 for every external server to be added to the server group named in step 3.
  5. deadtime minutes
  6. commit
  7. show radius server-groups [group-name [detail]]

DETAILED STEPS

Step 1

configure

Step 2

aaa group server radius group-name

Example:

 RP/0/RP0/CPU0:router(config)# aaa group server radius radgroup1

Groups different server hosts into distinct lists and enters the server group configuration mode.

Step 3

server {hostname | ip-address} [auth-port port-number] [acct-port port-number]

Example:

 RP/0/RP0/CPU0:router(config-sg-radius)# server 192.168.20.0

Specifies the hostname or IP address of an external RADIUS server.

  • After the server group is configured, it can be referenced from the AAA method lists (used while configuring authentication, authorization, or accounting).

Step 4

Repeat step 4 for every external server to be added to the server group named in step 3.

—
Step 5

deadtime minutes

Example:

 RP/0/RP0/CPU0:router(config-sg-radius)# deadtime 1

Configures the deadtime value at the RADIUS server group level.

  • The minutes argument specifies the length of time, in minutes, for which a RADIUS server is skipped over by transaction requests, up to a maximum of 1440 (24 hours). The range is from 1 to 1440.

The example specifies a one-minute deadtime for RADIUS server group radgroup1 when it has failed to respond to authentication requests for the deadtime command

Note 

You can configure the group-level deadtime after the group is created.

Step 6

commit

Step 7

show radius server-groups [group-name [detail]]

Example:

 RP/0/RP0/CPU0:router# show radius server-groups

(Optional) Displays information about each RADIUS server group that is configured in the system.

What to do next

After configuring RADIUS server groups, define method lists by configuring authentication, authorization, and accounting.

Configure TACACS+ Server Groups

This task configures TACACS+ server groups.

You can enter one or more server commands. The server command specifies the hostname or IP address of an external TACACS+ server. Once configured, this server group can be referenced from the AAA method lists (used while configuring authentication, authorization, or accounting).

Before you begin

For successful configuration, the external server should be accessible at the time of configuration. When configuring the same IP address for global and vrf configuration, server-private parameters are required (see Configure Per VRF TACACS+ Server Groups.

SUMMARY STEPS

  1. configure
  2. aaa group server tacacs+ group-name
  3. server {hostname | ip-address}
  4. Repeat step 3 for every external server to be added to the server group named in step 2.
  5. server-private {hostname | ip-address in IPv4 or IPv6 format} [port port-number] [timeout seconds] [key string]
  6. (Optional) vrf vrf-id
  7. commit
  8. show tacacs server-groups

DETAILED STEPS

Step 1

configure

Step 2

aaa group server tacacs+ group-name

Example:

RP/0/RP0/CPU0:router(config)# aaa group server tacacs+ tacgroup1

Groups different server hosts into distinct lists and enters the server group configuration mode.

Step 3

server {hostname | ip-address}

Example:

RP/0/RP0/CPU0:router(config-sg-tacacs+)# server 192.168.100.0

Specifies the hostname or IP address of an external TACACS+ server.

  • When configured, this group can be referenced from the AAA method lists (used while configuring authentication, authorization, or accounting).

Step 4

Repeat step 3 for every external server to be added to the server group named in step 2.

—
Step 5

server-private {hostname | ip-address in IPv4 or IPv6 format} [port port-number] [timeout seconds] [key string]

Example:

 Router(config-sg-tacacs+)# server-private 10.1.1.1 key a_secret

Configures the IP address of the private TACACS+ server for the group server.

Note 

If private server parameters are not specified, global configurations are used. If global configurations are not specified, default values are used.

Step 6

(Optional) vrf vrf-id

Example:

 Router(config-sg-tacacs+)# vrf test-vrf

The vrf option specifies the Virtual Private Network (VPN) routing and forwarding (VRF) reference of an AAA TACACS+ server group.

Step 7

commit

Step 8

show tacacs server-groups

Example:

RP/0/RP0/CPU0:router# show tacacs server-groups

(Optional) Displays information about each TACACS+ server group that is configured in the system.

Configure Per VRF TACACS+ Server Groups

The Cisco IOS XR software supports per VRF AAA to be configured on TACACS+ server groups. You must use the server-private and vrf commands as listed below to configure this feature.

The global server definitions can be referred from multiple server groups, but all references use the same server instance and connect to the same server. In case of VRF, you do not need the global configuration because the server status, server statistics and the key could be different for different VRFs. Therefore, you must use the server-private configuration if you want to configure per VRF TACACS+ server groups. If you have the same server used in different groups with different VRFs, ensure that it is reachable through all those VRFs.

If you are migrating the servers to a VRF, then it is safe to remove the global server configuration with respect to that server.

Prerequisites

You must ensure these before configuring per VRF on TACACS+ server groups:

  • Be familiar with configuring TACACS+, AAA, per VRF AAA, and group servers.

  • Ensure that you have access to the TACACS+ server.

  • Configure the VRF instance before configuring the specific VRF for a TACACS+ server and ensure that the VRF is reachable.

Configuration Example


Router#configure

/* Groups different server hosts into distinct lists and enters the server group configuration mode.
You can enter one or more server commands. The server command specifies the hostname or IP address of an external TACACS+ server.
Once configured, this server group can be referenced from the AAA method lists (used while configuring authentication, authorization, or accounting). */

Router(config)# aaa group server tacacs+ tacgroup1

/* Configures the IP address and the secret key of the private TACACS+ server that is reachable through specific VRF. 
You can have multiple such server configurations which are reachable through the same VRF.*/

Router(config-sg-tacacs+)# server-private 10.1.1.1 port 49 key a_secret

/* The vrf option specifies the VRF reference of a AAA TACACS+ server group */
Router(config-sg-tacacs+)# vrf test-vrf
Router(config-sg-tacacs+)# commit

Running Configuration


aaa group server tacacs+ tacgroup1
 vrf test-vrf
 server-private 10.1.1.1 port 49
  key 7 0822455D0A16
 !
 server-private 10.1.1.2 port 49
  key 7 05080F1C2243
 !
 server-private 2001:db8:1::1 port 49
  key 7 045802150C2E
 !
 server-private 2001:db8:1::2 port 49
  key 7 13061E010803
 !
!

Verify Per VRF TACACS+ Server Groups


Router#show tacacs
Fri Sep 27 11:14:34.991 UTC

Server: 10.1.1.1/49 vrf=test-vrf [private]
        opens=0 closes=0 aborts=0 errors=0
        packets in=0 packets out=0
        status=up single-connect=false family=IPv4

Server: 10.1.1.2/49 vrf=test-vrf [private]
        opens=0 closes=0 aborts=0 errors=0
        packets in=0 packets out=0
        status=up single-connect=false family=IPv4

Server: 2001:db8:1::1/49 vrf=test-vrf [private]
        opens=0 closes=0 aborts=0 errors=0
        packets in=0 packets out=0
        status=up single-connect=false family=IPv6

Server: 2001:db8:1::2/49 vrf=test-vrf [private]
        opens=0 closes=0 aborts=0 errors=0
        packets in=0 packets out=0
        status=up single-connect=false family=IPv6

Associated Commands

  • server-private

  • vrf

Create Series of Authentication Methods

Authentication is the process by which a user (or a principal) is verified. Authentication configuration uses method lists to define an order of preference for the source of AAA data, which may be stored in a variety of data sources. You can configure authentication to define more than one method list and applications (such as login) can choose one of them. For example, console ports may use one method list and the vty ports may use another. If a method list is not specified, the application tries to use a default method list.


Note

Applications should explicitly refer to defined method lists for the method lists to be effective.

The authentication can be applied to tty lines through use of the login authentication line configuration submode command. If the method is RADIUS or TACACS+ servers, rather than server group, the RADIUS or TACACS+ server is chosen from the global pool of configured RADIUS and TACACS+ servers, in the order of configuration. Servers from this global pool are the servers that can be selectively added to a server group.

The subsequent methods of authentication are used only if the initial method returns an error, not if the request is rejected.

Before you begin


Note

The default method list is applied for all the interfaces for authentication, except when a non-default named method list is explicitly configured, in which case the named method list is applied.

The group radius, group tacacs+ , and group group-name forms of the aaa authentication command refer to a set of previously defined RADIUS or TACACS+ servers. Use the radius server-host or tacacs-server host command to configure the host servers. Use the aaa group server radius or aaa group server tacacs+ command to create a named group of servers.

SUMMARY STEPS

  1. configure
  2. aaa authentication {login} {default | list-name} method-list
  3. commit
  4. Repeat Step 1 through Step 3 for every authentication method list to be configured.

DETAILED STEPS

Step 1

configure

Step 2

aaa authentication {login} {default | list-name} method-list

Example:


RP/0//CPU0:router(config)# aaa authentication login default group tacacs+

Creates a series of authentication methods, or a method list.

  • Using the login keyword sets authentication for login. Using the ppp keyword sets authentication for Point-to-Point Protocol.

  • Entering the default keyword causes the listed authentication methods that follow this keyword to be the default list of methods for authentication.

  • Entering a list-name character string identifies the authentication method list.

  • Entering a method-list argument following the method list type. Method list types are entered in the preferred sequence. The listed method types are any one of the following options:

    • group tacacs+—Use a server group or TACACS+ servers for authentication

    • group radius—Use a server group or RADIUS servers for authentication

    • group named-group —Use a named subset of TACACS+ or RADIUS servers for authentication

    • local—Use a local username or password database for authentication

    • line—Use line password or user group for authentication

  • The example specifies the default method list to be used for authentication.

Step 3

commit

Step 4

Repeat Step 1 through Step 3 for every authentication method list to be configured.

—

Create Series of Authorization Methods

Method lists for authorization define the ways authorization will be performed and the sequence in which these methods will be performed. A method list is a named list describing the authorization methods to be used (such as TACACS+), in sequence. Method lists enable you to designate one or more security protocols to be used for authorization, thus ensuring a backup system if the initial method fails. The software uses the first method listed to authorize users for specific network services; if that method fails to respond, the software selects the next method listed in the method list. This process continues until there is successful communication with a listed authorization method, or until all methods defined have been exhausted.


Note

The software attempts authorization with the next listed method only when there is no response or an error response (not a failure) from the previous method. If authorization fails at any point in this cycle—meaning that the security server or local username database responds by denying the user services—the authorization process stops and no other authorization methods are attempted.

When you create a named method list, you are defining a particular list of authorization methods for the indicated authorization type. When defined, method lists must be applied to specific lines or interfaces before any of the defined methods are performed. Do not use the names of methods, such as TACACS+, when creating a new method list.

“Command” authorization, as a result of adding a command authorization method list to a line template, is separate from, and is in addition to, “task-based” authorization, which is performed automatically on the router. The default behavior for command authorization is none. Even if a default method list is configured, that method list has to be added to a line template for it to be used.

The aaa authorization commands command causes a request packet containing a series of attribute value (AV) pairs to be sent to the TACACS+ daemon as part of the authorization process. The daemon can do one of the following:

  • Accept the request as is.

  • Refuse authorization.

Use the aaa authorization command to set parameters for authorization and to create named method lists defining specific authorization methods that can be used for each line or interface.

SUMMARY STEPS

  1. configure
  2. aaa authorization {commands | eventmanager | exec | network} {default | list-name} {none | local | group {tacacs+ | radius | group-name}}
  3. commit

DETAILED STEPS

Step 1

configure

Step 2

aaa authorization {commands | eventmanager | exec | network} {default | list-name} {none | local | group {tacacs+ | radius | group-name}}

Example:


RP/0//CPU0:router(config)# aaa authorization commands listname1 group tacacs+

Creates a series of authorization methods, or a method list.

  • The commands keyword configures authorization for all XR EXEC mode shell commands. Command authorization applies to the EXEC mode commands issued by a user. Command authorization attempts authorization for all XR EXEC modecommands.

  • The eventmanager keyword applies an authorization method for authorizing an event manager (fault manager).

  • The exec keyword configures authorization for an interactive (XR EXEC mode) session.

  • The network keyword configures authorization for network services like PPP or IKE.

  • The default keyword causes the listed authorization methods that follow this keyword to be the default list of methods for authorization.

  • A list-name character string identifies the authorization method list. The method list itself follows the method list name. Method list types are entered in the preferred sequence. The listed method list types can be any one of the following:

    • none —The network access server (NAS) does not request authorization information. Authorization always succeeds. No subsequent authorization methods will be attempted. However, the task ID authorization is always required and cannot be disabled.

    • local—Uses local database for authorization.

  • group tacacs+ —Uses the list of all configured TACACS+ servers for authorization. The NAS exchanges authorization information with the TACACS+ security daemon. TACACS+ authorization defines specific rights for users by associating AV pairs, which are stored in a database on the TACACS+ security server, with the appropriate user.

  • group radius —Uses the list of all configured RADIUS servers for authorization.

  • group group-name —Uses a named server group, a subset of TACACS+ or RADIUS servers for authorization as defined by the aaa group server tacacs+ or aaa group server radius command.

Step 3

commit

Create Series of Accounting Methods

Use the aaa accounting command to create default or named method lists defining specific accounting methods that can be used for each line or interface.

Currently, the software supports both the TACACS+ and RADIUS methods for accounting. The router reports user activity to the TACACS+ or RADIUS security server in the form of accounting records. Each accounting record contains accounting AV pairs and is stored on the security server.

Method lists for accounting define the way accounting is performed, enabling you to designate a particular security protocol to be used on specific lines or interfaces for particular types of accounting services. When naming a method list, do not use the names of methods, such as TACACS+.

For minimal accounting, include the stop-only keyword to send a “stop accounting” notice at the end of the requested user process. For more accounting, you can include the start-stop keyword, so that the external AAA server sends a “start accounting” notice at the beginning of the requested process and a “stop accounting” notice at the end of the process. In addition, you can use the aaa accounting update command to periodically send update records with accumulated information. Accounting records are stored only on the TACACS+ or RADIUS server.

When AAA accounting is activated, the router reports these attributes as accounting records, which are then stored in an accounting log on the security server.

SUMMARY STEPS

  1. configure
  2. Do one of the following:
    • aaa accounting {commands | exec | network} {default | list-name} {start-stop | stop-only}
    • {none | method}
  3. commit

DETAILED STEPS

Step 1

configure

Step 2

Do one of the following:

  • aaa accounting {commands | exec | network} {default | list-name} {start-stop | stop-only}
  • {none | method}

Example:


RP/0//CPU0:router(config)# aaa accounting commands default stop-only group tacacs+
Note 

Command accounting is not supported on RADIUS, but supported on TACACS.

Creates a series of accounting methods, or a method list.

  • The commands keyword enables accounting for XR EXEC mode shell commands.

  • The exec keyword enables accounting for an interactive (XR EXEC mode) session.

  • The network keyword enables accounting for all network-related service requests, such as Point-to-Point Protocol (PPP).

  • The default keyword causes the listed accounting methods that follow this keyword to be the default list of methods for accounting.

  • A list-name character string identifies the accounting method list.

  • The start-stop keyword sends a “start accounting” notice at the beginning of a process and a “stop accounting” notice at the end of a process. The requested user process begins regardless of whether the “start accounting” notice was received by the accounting server.

  • The stop-only keyword sends a “stop accounting” notice at the end of the requested user process.

  • The none keyword states that no accounting is performed.

  • The method list itself follows the start-stop keyword. Method list types are entered in the preferred sequence. The method argument lists the following types:

    • group tacacs+ —Use the list of all configured TACACS+ servers for accounting.

    • group radius— Use the list of all configured RADIUS servers for accounting.

    • group group-name —Use a named server group, a subset of TACACS+ or RADIUS servers for accounting as defined by the aaa group server tacacs+ or aaa group server radius command.

  • The example defines a default command accounting method list, in which accounting services are provided by a TACACS+ security server, with a stop-only restriction.

Step 3

commit

Generate Interim Accounting Records

This task enables periodic interim accounting records to be sent to the accounting server. When the aaa accounting update command is activated, software issues interim accounting records for all users on the system.


Note

Interim accounting records are generated only for network sessions, such as Internet Key Exchange (IKE) accounting, which is controlled by the aaa accounting command with the network keyword. System, command, or EXEC accounting sessions cannot have interim records generated.

SUMMARY STEPS

  1. configure
  2. aaa accounting update {newinfo | periodic minutes}
  3. commit

DETAILED STEPS

Step 1

configure

Step 2

aaa accounting update {newinfo | periodic minutes}

Example:


RP/0//CPU0:router(config)# aaa accounting update periodic 30

Enables periodic interim accounting records to be sent to the accounting server.

  • If the newinfo keyword is used, interim accounting records are sent to the accounting server every time there is new accounting information to report. An example of this report would be when IPCP completes IP address negotiation with the remote peer. The interim accounting record includes the negotiated IP address used by the remote peer.

  • When used with the periodic keyword, interim accounting records are sent periodically as defined by the argument number. The interim accounting record contains all the accounting information recorded for that user up to the time the interim accounting record is sent.

Caution 

The periodic keyword causes heavy congestion when many users are logged in to the network.

Step 3

commit

Apply Method List

After you use the aaa authorization command to define a named authorization method list (or use the default method list) for a particular type of authorization, you must apply the defined lists to the appropriate lines in order for authorization to take place. Use the authorization command to apply the specified method lists (or, if none is specified, the default method list) to the selected line or group of lines.

SUMMARY STEPS

  1. configure
  2. line { console | default | template template-name}
  3. authorization {commands | exec} {default | list-name}
  4. commit

DETAILED STEPS

Step 1

configure

Step 2

line { console | default | template template-name}

Example:


RP/0//CPU0:router(config)# line console

Enters line template configuration mode.

Step 3

authorization {commands | exec} {default | list-name}

Example:


RP/0//CPU0:router(config-line)# authorization commands listname5

Enables AAA authorization for a specific line or group of lines.

  • The commands keyword enables authorization on the selected lines for all commands.

  • The exec keyword enables authorization for an interactive (XR EXEC mode) session.

  • Enter the default keyword to apply the name of the default method list, as defined with the aaa authorization command.

  • Enter the name of a list of authorization methods to use. If no list name is specified, the system uses the default. The list is created with the aaa authorization command.

  • The example enables command authorization using the method list named listname5.

Step 4

commit

What to do next

After applying authorization method lists by enabling AAA authorization, apply accounting method lists by enabling AAA accounting.

Enable Accounting Services

This task enables accounting services for a specific line of group of lines.

SUMMARY STEPS

  1. configure
  2. line { console | default | template template-name}
  3. accounting {commands | exec} {default | list-name}
  4. commit

DETAILED STEPS

Step 1

configure

Step 2

line { console | default | template template-name}

Example:


RP/0//CPU0:router(config)# line console

Enters line template configuration mode.

Step 3

accounting {commands | exec} {default | list-name}

Example:


RP/0//CPU0:router(config-line)# accounting commands listname7

Enables AAA accounting for a specific line or group of lines.

  • The commands keyword enables accounting on the selected lines for all XR EXEC mode shell commands.

  • The exec keyword enables accounting for an interactive (XR EXEC mode) session.

  • Enter the default keyword to apply the name of the default method list, as defined with the aaa accounting command.

  • Enter the name of a list of accounting methods to use. If no list name is specified, the system uses the default. The list is created with the aaa accounting command.

  • The example enables command accounting using the method list named listname7.

Step 4

commit

What to do next

After applying accounting method lists by enabling AAA accounting services, configure login parameters.

Configure Login Parameters

This task sets the interval that the server waits for reply to a login.

SUMMARY STEPS

  1. configure
  2. line template template-name
  3. timeout login response seconds
  4. commit

DETAILED STEPS

Step 1

configure

Step 2

line template template-name

Example:


RP/0//CPU0:router(config)# line template alpha

Specifies a line to configure and enters line template configuration mode.

Step 3

timeout login response seconds

Example:


RP/0//CPU0:router(config-line)# timeout login response 20

Sets the interval that the server waits for reply to a login.

  • The seconds argument specifies the timeout interval (in seconds) from 0 to 300. The default is 30 seconds.

  • The example shows how to change the interval timer to 20 seconds.

Step 4

commit

Task Maps

For users who are authenticated using an external TACACS+ server and RADIUS server, Cisco IOS XR software AAA supports a method to define task IDs remotely.

Format of the Task String

The task string in the configuration file of the TACACS+ server consists of tokens delimited by a comma (,). Each token contains either a task ID name and its permissions or the user group to include for this particular user, as shown in the following example:

task = “ permissions : taskid name , # usergroup name , ...”


Note

Cisco IOS XR software allows you to specify task IDs as an attribute in the external RADIUS or TACACS+ server. If the server is also shared by non-Cisco IOS XR software systems, these attributes are marked as optional as indicated by the server documentation. For example, CiscoSecure ACS and the freeware TACACS+ server from Cisco require an asterisk (*) instead of an equal sign (=) before the attribute value for optional attributes. If you want to configure attributes as optional, refer to the TACACS+ server documentation.

For example, to give a user named user1 BGP read, write, and execute permissions and include user1 in a user group named operator, the username entry in the external server’s TACACS+ configuration file would look similar to the following: 


user = user1{
member = some-tac-server-group
opap = cleartext "lab"
service = exec {
task = "rwx:bgp,#operator"
}
}

The r,w,x, and d correspond to read, write, execute and debug, respectively, and the pound sign (#) indicates that a user group follows.


Note

The optional keyword must be added in front of “task” to enable interoperability with systems based on Cisco IOS software.

If CiscoSecure ACS is used, perform the following procedure to specify the task ID and user groups:

SUMMARY STEPS

  1. Enter your username and password.
  2. Click the Group Setup button to display the Group Setup window.
  3. From the Group drop-down list, select the group that you want to update.
  4. Click the Edit Settings button.
  5. Use the scroll arrow to locate the Shell (exec) check box.
  6. Check the Shell (exec) check box to enable the custom attributes configuration.
  7. Check the Custom attributes check box.
  8. Enter the following task string without any blank spaces or quotation marks in the field:
  9. Click the Submit + Restart button to restart the server.

DETAILED STEPS

Step 1

Enter your username and password.

Step 2

Click the Group Setup button to display the Group Setup window.

Step 3

From the Group drop-down list, select the group that you want to update.

Step 4

Click the Edit Settings button.

Step 5

Use the scroll arrow to locate the Shell (exec) check box.

Step 6

Check the Shell (exec) check box to enable the custom attributes configuration.

Step 7

Check the Custom attributes check box.

Step 8

Enter the following task string without any blank spaces or quotation marks in the field:

Example:


task=rwx:bgp,#netadmin
Step 9

Click the Submit + Restart button to restart the server.

The following RADIUS Vendor-Specific Attribute (VSA) example shows that the user is part of the sysadmin predefined task group, can configure BGP, and can view the configuration for OSPF:

Example:


user Auth-Type := Local, User-Password == lab
        Service-Type = NAS-Prompt-User,
        Reply-Message = "Hello, %u",
        Login-Service = Telnet,
        Cisco-AVPair = "shell:tasks=#sysadmin,rwx:bgp,r:ospf"

After user1 successfully connects and logs in to the external TACACS+ server with username user1 and appropriate password, the show user tasks command can be used in XR EXEC mode to display all the tasks user1 can perform. For example:

Example:


Username:user1
Password:
RP/0/RP0/CPU0:router# show user tasks

Task:      basic-services  :READ    WRITE    EXECUTEDEBUG
Task:                 bgp  :READ    WRITE    EXECUTE
Task:                 cdp  :READ
Task:                diag  :READ
Task:          ext-access  :READ             EXECUTE
Task:             logging  :READ

Alternatively, if a user named user2, who does not have a task string, logs in to the external server, the following information is displayed:

Example:


Username:user2
Password:
RP/0/RP0/CPU0:router# show user tasks
No task ids available

References for AAA Services

This section lists all the conceptual information that a software user must understand before configuring user groups and task groups through AAA or configuring Remote Authentication Dial-in User Service (RADIUS) or TACACS+ servers. Conceptual information also describes what AAA is and why it is important.

User, User Groups, and Task Groups

User attributes form the basis of the Cisco software administrative model. Each router user is associated with the following attributes:

  • User ID (ASCII string) that identifies the user uniquely across an administrative domain

  • Length limitation of 253 characters for passwords and one-way encrypted secrets

  • List of user groups (at least one) of which the user is a member (thereby enabling attributes such as task IDs).

User Categories

Router users are classified into the following categories:

  • Root Secure Domain Router (SDR) user (specific SDR administrative authority)

  • SDR user (specific SDR user access)

Root System Users

The root system user is the entity authorized to “own” the entire router chassis. The root system user functions with the highest privileges over all router components and can monitor all secure domain routers in the system. At least one root system user account must be created during router setup. Multiple root system users can exist.

The root system user can perform any configuration or monitoring task, including the following:

  • Configure secure domain routers.

  • Create, delete, and modify root SDR users (after logging in to the secure domain router as the root system user).

  • Create, delete, and modify secure domain router users and set user task permissions (after logging in to the secure domain router as the root system user).

  • Access fabric racks or any router resource not allocated to a secure domain router, allowing the root system user to authenticate to any router node regardless of the secure domain router configurations.

Root SDR Users

A root SDR user controls the configuration and monitoring of a particular SDR. The root SDR user can create users and configure their privileges within the SDR. Multiple root SDR users can work independently. A single SDR may have more than one root SDR user.

A root SDR user can perform the following administrative tasks for a particular SDR:

  • Create, delete, and modify secure domain router users and their privileges for the SDR.

  • Create, delete, and modify user groups to allow access to the SDR.

  • Manage nearly all aspects of the SDR.

A root SDR user cannot deny access to a root system user.

Secure Domain Router (SDR) Users

A SDR user has restricted access to an SDR as determined by the root SDR user. The SDR user performs the day-to-day system and network management activities. The tasks that the secure domain router user is allowed to perform are determined by the task IDs associated with the user groups to which the SDR user belongs. Multiple SDRs in a chasis are not supported.

User Groups

A user group defines a collection of users that share a set of attributes, such as access privileges. Cisco software allows the system administrator to configure groups of users and the job characteristics that are common in groups of users. Users are not assigned to groups by default hence the assignment needs to be done explicitly. A user can be assigned to more than one group.

Each user may be associated with one or more user groups. User groups have the following attributes:

  • A user group consists of the list of task groups that define the authorization for the users. All tasks, except cisco-support, are permitted by default for root system users.

  • Each user task can be assigned read, write, execute, or debug permission.

Predefined User Groups

The Cisco software provides a collection of user groups whose attributes are already defined. The predefined groups are as follows:

  • cisco-support: This group is used by the Cisco support team.

  • netadmin: Has the ability to control and monitor all system and network parameters.

  • operator: A demonstration group with basic privileges.

  • root-lr: Has the ability to control and monitor the specific secure domain router.

  • sysadmin: Has the ability to control and monitor all system parameters but cannot configure network protocols.

  • serviceadmin: Service administration tasks, for example, Session Border Controller (SBC).

User-Defined User Groups

Administrators can configure their own user groups to meet particular needs.

User Group Inheritance

A user group can derive attributes from another user group. (Similarly, a task group can derive attributes from another task group). For example, when user group A inherits attributes from user group B, the new set of task attributes of the user group A is a union of A and B. The inheritance relationship among user groups is dynamic in the sense that if group A inherits attributes from group B, a change in group B affects group A, even if the group is not reinherited explicitly.

Task Groups

Task groups are defined by lists of permitted task IDs for each type of action (such as read, write, and so on). The task IDs are basically defined in the router system. Task ID definitions may have to be supported before task groups in external software can be configured.

Task IDs can also be configured in external TACACS+ or RADIUS servers.

Predefined Task Groups

The following predefined task groups are available for administrators to use, typically for initial configuration:

  • cisco-support: Cisco support personnel tasks

  • netadmin: Network administrator tasks

  • operator: Operator day-to-day tasks (for demonstration purposes)

  • root-lr: Secure domain router administrator tasks

  • sysadmin: System administrator tasks

  • serviceadmin: Service administration tasks, for example, SBC

User-Defined Task Groups

Users can configure their own task groups to meet particular needs.

Group Inheritance

Task groups support inheritance from other task groups. (Similarly, a user group can derive attributes from another user group. For example, when task group A inherits task group B, the new set of attributes of task group A is the union of A and B.

Command Access in XR and Admin Modes

The XR user group and task is mapped to the System Admin VM group when the System Admin mode is accessed from XR mode using admin command. The corresponding access permission on System Admin VM is available to the user. Currently, only aaa, admin task and root-lr groups are mapped to System Admin VM group or task. The other tasks like protocols are not mapped as these services are not supported in System Admin VM. The disaster-recovery user of System Admin VM is synced with the Host VM.

XR Task or Group

Sysadmin VM Group

Access

Example

root-lr

Root-system group

Full access to the system configuration. 

RP/0/RP0/CPU0:ios#show user group
Mon Nov  3 13:48:54.536 UTC
root-lr, cisco-support
RP/0/RP0/CPU0:ios#show user tasks | inc root-lr
Mon Nov  3 13:49:06.495 UTC
Task:              root-lr  : READ    WRITE    EXECUTE    DEBUG (reserved)

RP/0/RP0/CPU0:ios#admin
sysadmin-vm:0_RP0# show aaa user-group
Mon Nov  3  13:48:00.790 UTC
User group : root-system

Admin-r/w/x/d

Admin-r

Read only commands on Sysadmin VM 

taskgroup tg-admin-write
 task write admin
 task execute admin
!
usergroup ug-admin-write
 taskgroup tg-admin-write
!
username admin-write
 group ug-admin-write
 password admin-write
!
RP/0/RP0/CPU0:ios#show user group
Mon Nov  3 14:09:29.676 UTC
ug-admin-write
RP/0/RP0/CPU0:ios#show user tasks
Mon Nov  3 14:09:35.244 UTC
Task:                admin  : READ    WRITE    EXECUTE

RP/0/RP0/CPU0:ios#admin
Mon Nov  3 14:09:40.401 UTC
admin-write connected from 127.0.0.1 using console on xr-vm_node0_RP0_CPU0
sysadmin-vm:0_RP0# show aaa user-group Mon Nov 3 13:53:00.790 UTC User group : admin-r

Netadmin or sysadmin group

Admin-r/ wx /d, aaa -r/w/x/d

Aaa -r and admin -r

Read only commands on Sysadmin VM 

RP/0/RP0/CPU0:ios#show user group
Mon Nov  3 13:44:39.176 UTC
netadmin
RP/0/RP0/CPU0:ios#show user tasks  | inc aaa
Mon Nov  3 13:45:00.999 UTC
Task:                  aaa  : READ
RP/0/RP0/CPU0:ios#show user tasks  | inc admin
Mon Nov  3 13:45:09.567 UTC
Task:                admin  : READ

RP/0/RP0/CPU0:ios#admin
Mon Nov  3 13:46:21.183 UTC
netadmin connected from 127.0.0.1 using console on xr-vm_node0_RP0_CPU0
sysadmin-vm:0_RP0# show aaa user-group
Mon Nov  3  13:44:23.939 UTC
User group : admin-r,aaa-r
sysadmin-vm:0_RP0#

Administrative Model

The router operates in two planes: the administration (admin) plane and secure domain router (SDR) plane. The admin (shared) plane consists of resources shared across all SDRs, while the SDR plane consists of those resources specific to the particular SDR.

Each SDR has its own AAA configuration including, local users, groups, and TACACS+ and RADIUS configurations. Users created in one SDR cannot access other SDRs unless those same users are configured in the other SDRs.

Administrative Access

Administrative access to the system can be lost if the following operations are not well understood and carefully planned.

  • Configuring authentication that uses remote AAA servers that are not available, particularly authentication for the console.


Note

The none option without any other method list is not supported.

  • Configuring command authorization or XR EXEC mode authorization on the console should be done with extreme care, because TACACS+ servers may not be available or may deny every command, which locks the user out. This lockout can occur particularly if the authentication was done with a user not known to the TACACS+ server, or if the TACACS+ user has most or all the commands denied for one reason or another.

To avoid a lockout, we recommend one or both of the following:

  • Before turning on TACACS+ command authorization or XR EXEC mode authorization on the console, make sure that the user who is configuring the authorization is logged in using the appropriate user permissions in the TACACS+ profile.

  • If the security policy of the site permits it, use the none option for command authorization or XR EXEC mode authorization so that if the TACACS+ servers are not reachable, AAA rolls over to the none method, which permits the user to run the command.

AAA Database

The AAA database stores the users, groups, and task information that controls access to the system. The AAA database can be either local or remote. The database that is used for a specific situation depends on the AAA configuration.

Local Database

AAA data, such as users, user groups, and task groups, can be stored locally within a secure domain router. The data is stored in the in-memory database and persists in the configuration file. The stored passwords are encrypted.


Note

The database is local to the specific secure domain router (SDR) in which it is stored, and the defined users or groups are not visible to other SDRs in the same system.

You can delete the last remaining user from the local database. If all users are deleted when the next user logs in, the setup dialog appears and prompts you for a new username and password.


Note

The setup dialog appears only when the user logs into the console.

Remote Database

AAA data can be stored in an external security server, such as CiscoSecure ACS. Security data stored in the server can be used by any client (such as a network access server [NAS]) provided that the client knows the server IP address and shared secret.

Remote AAA Configuration

Products such as CiscoSecure ACS can be used to administer the shared or external AAA database. The router communicates with the remote AAA server using a standard IP-based security protocol (such as TACACS+ or RADIUS).

Client Configuration

The security server should be configured with the secret key shared with the router and the IP addresses of the clients.

User Groups

User groups that are created in an external server are not related to the user group concept that is used in the context of local AAA database configuration on the router. The management of external TACACS+ server or RADIUS server user groups is independent, and the router does not recognize the user group structure. The remote user or group profiles may contain attributes that specify the groups (defined on the router) to which a user or users belong, as well as individual task IDs.

Configuration of user groups in external servers comes under the design of individual server products. See the appropriate server product documentation.

Task Groups

Task groups are defined by lists of permitted task IDs for each type of action (such as read, write, and so on). The task IDs are basically defined in the router system. Task ID definitions may have to be supported before task groups in external software can be configured.

Task IDs can also be configured in external TACACS+ or RADIUS servers.

AAA Configuration

This section provides information about AAA configuration.

Method Lists

AAA data may be stored in a variety of data sources. AAA configuration uses method lists to define an order of preference for the source of AAA data. AAA may define more than one method list and applications (such as login) can choose one of them. For example, console ports may use one method list and the vty ports may use another. If a method list is not specified, the application tries to use a default method list. If a default method list does not exist, AAA uses the local database as the source.

Rollover Mechanism

AAA can be configured to use a prioritized list of database options. If the system is unable to use a database, it automatically rolls over to the next database on the list. If the authentication, authorization, or accounting request is rejected by any database, the rollover does not occur and the request is rejected.

The following methods are available:

  • Local: Use the locally configured database (not applicable for accounting and certain types of authorization)

  • TACACS+: Use a TACACS+ server (such as CiscoSecure ACS)

  • RADIUS: Use a RADIUS server

  • Line: Use a line password and user group (applicable only for authentication)

  • None: Allow the request (not applicable for authentication)

Server Grouping

Instead of maintaining a single global list of servers, the user can form server groups for different AAA protocols (such as RADIUS and TACACS+) and associate them with AAA applications (such as PPP and XR EXEC mode).

Authentication

Authentication is the most important security process by which a principal (a user or an application) obtains access to the system. The principal is identified by a username (or user ID) that is unique across an administrative domain. The applications serving the user (such as or Management Agent) procure the username and the credentials from the user. AAA performs the authentication based on the username and credentials passed to it by the applications. The role of an authenticated user is determined by the group (or groups) to which the user belongs. (A user can be a member of one or more user groups.)

Authentication of Non-Owner Secure Domain Router User

When logging in from a non-owner secure domain router, the root system user must add the “@admin” suffix to the username. Using the “@admin” suffix sends the authentication request to the owner secure domain router for verification. The owner secure domain router uses the methods in the list-name remote for choosing the authentication method. The remote method list is configured using the aaa authentication login remote method1 method2 ... command.

Authentication of Owner Secure Domain Router User

An owner secure domain router user can log in only to the nodes belonging to the specific secure domain router associated with that owner secure domain router user. If the user is member of a root-sdr group, the user is authenticated as an owner secure domain router user.

Authentication of Secure Domain Router User

Secure domain router user authentication is similar to owner secure domain router user authentication. If the user is not found to be a member of the designated owner secure domain router user group, the user is authenticated as a secure domain router user.

Authentication Flow of Control

AAA performs authentication according to the following process:

  1. A user requests authentication by providing a username and password (or secret).

  2. AAA verifies the user’s password and rejects the user if the password does not match what is in the database.

  3. AAA determines the role of the user (root SDR user, or SDR user).

  • If the user has been configured as a member of an owner secure domain router user group, then AAA authenticates the user as an owner secure domain router user.

  • If the user has not been configured as a member of an owner secure domain router user group, AAA authenticates the user as a secure domain router user.

Clients can obtain a user’s permitted task IDs during authentication. This information is obtained by forming a union of all task group definitions specified in the user groups to which the user belongs. Clients using such information typically create a session for the user (such as an API session) in which the task ID set remains static. Both the XR EXEC mode and external API clients can use this feature to optimize their operations. XR EXEC mode can avoid displaying the commands that are not applicable and an EMS application can, for example, disable graphical user interface (GUI) menus that are not applicable.

If the attributes of a user, such as user group membership and, consequently, task permissions, are modified, those modified attributes are not reflected in the user’s current active session; they take effect in the user’s next session.

Password Types

In configuring a user and that user’s group membership, you can specify two types of passwords: encrypted or clear text.

The router supports both two-way and one-way (secret) encrypted user passwords. Secret passwords are ideal for user login accounts because the original unencrypted password string cannot be deduced on the basis of the encrypted secret. Some applications (PPP, for example) require only two-way passwords because they must decrypt the stored password for their own function, such as sending the password in a packet. For a login user, both types of passwords may be configured, but a warning message is displayed if one type of password is configured while the other is already present.

If both secret and password are configured for a user, the secret takes precedence for all operations that do not require a password that can be decrypted, such as login. For applications such as PPP, the two-way encrypted password is used even if a secret is present.

Task-based Authorization

AAA employs “task permissions” for any control, configure, or monitor operation through CLI or API. The Cisco IOS software concept of privilege levels has been replaced in software by a task-based authorization system.

Task IDs

The operational tasks that enable users to control, configure, and monitor Cisco software are represented by task IDs. A task ID defines the permission to run an operation for a command. Users are associated with sets of task IDs that define the breadth of their authorized access to the router.

Task IDs are assigned to users through the following means:

Each user is associated with one or more user groups. Every user group is associated with one or more task groups; in turn, every task group is defined by a set of task IDs. Consequently, a user’s association with a particular user group links that user to a particular set of task IDs. A user that is associated with a task ID can execute any operation associated with that task ID.

General Usage Guidelines for Task IDs

Most router control, configuration, or monitoring operation (CLI, Netconf, Restconf, XML API) is associated with a particular set of task IDs. Typically, a given CLI command or API invocation is associated with at least one or more task IDs. Neither the config nor the commit commands require any specific task id permissions. The configuration and commit operations do not require specific task ID permissions. Aliases also don't require any task ID permissions. You cannnot perform a configuration replace unless root-lr permissions are assigned. If you want to deny getting into configuration mode you can use the TACACS+ command authorization to deny the config command. These associations are hard-coded within the router and may not be modified. Task IDs grant permission to perform certain tasks; task IDs do not deny permission to perform tasks. Task ID operations can be one, all, or a combination of classes that are listed in this table.


Note
Restconf will be supported in a future release.
Table 1. Task ID Classes

Operation

Description

Read

Specifies a designation that permits only a read operation.

Write

Specifies a designation that permits a change operation and implicitly allows a read operation.

Execute

Specifies a designation that permits an access operation; for example ping and Telnet.

Debug

Specifies a designation that permits a debug operation.

The system verifies that each CLI command and API invocation conforms with the task ID permission list for the user. If you are experiencing problems using a CLI command, contact your system administrator.

Multiple task ID operations separated by a slash (for example read/write) mean that both operations are applied to the specified task ID.

Multiple task ID operations separated by a comma (for example read/write, execute) mean that both operations are applied to the respective task IDs. For example, the copy ipv4 access-list command can have the read and write operations applied to the acl task ID, and the execute operation applied to the filesystem task ID.

If the task ID and operations columns have no value specified, the command is used without any previous association to a task ID and operation. In addition, users do not have to be associated to task IDs to use ROM monitor commands.

Users may need to be associated to additional task IDs to use a command if the command is used in a specific configuration submode. For example, to execute the show redundancy command, a user needs to be associated to the system (read) task ID and operations as shown in the following example: 


RP/0/RP0/CPU0:router# show redundancy

Task IDs for TACACS+ and RADIUS Authenticated Users

Cisco software AAA provides the following means of assigning task permissions for users authenticated with the TACACS+ and RADIUS methods:

  • Specify the text version of the task map directly in the configuration file of the external TACACS+ and RADIUS servers.

  • Specify the privilege level in the configuration file of the external TACACS+ and RADIUS servers.

  • Create a local user with the same username as the user authenticating with the TACACS+ and RADIUS methods.

  • Specify, by configuration, a default task group whose permissions are applied to any user authenticating with the TACACS+ and RADIUS methods.

Privilege Level Mapping

For compatibility with TACACS+ daemons that do not support the concept of task IDs, AAA supports a mapping between privilege levels defined for the user in the external TACACS+ server configuration file and local user groups. Following TACACS+ authentication, the task map of the user group that has been mapped from the privilege level returned from the external TACACS+ server is assigned to the user. For example, if a privilege level of 5 is returned from the external TACACS server, AAA attempts to get the task map of the local user group priv5. This mapping process is similar for other privilege levels from 1 to 13. For privilege level 14 maps to the user group owner-sdr.

For example, with the Cisco freeware tac plus server, the configuration file has to specify priv_lvl in its configuration file, as shown in the following example: 


user = sampleuser1{
    member = bar
    service = exec-ext {
        priv_lvl = 5
    }
}

The number 5 in this example can be replaced with any privilege level that has to be assigned to the user sampleuser.

XML Schema for AAA Services

The extensible markup language (XML) interface uses requests and responses in XML document format to configure and monitor AAA. The AAA components publish the XML schema corresponding to the content and structure of the data used for configuration and monitoring. The XML tools and applications use the schema to communicate to the XML agent for performing the configuration.

The following schema are published by AAA:

  • Authentication, Authorization and Accounting configuration

  • User, user group, and task group configuration

  • TACACS+ server and server group configuration

  • RADIUS server and server group configuration

Netconf and Restconf for AAA Services

Just as in XML schemas, in Netconf and Restconf, username and password is controlled by either local or triple A (AAA) services.


Note
Restconf will be supported in a future release.

About RADIUS

RADIUS is a distributed client/server system that secures networks against unauthorized access. In the Cisco implementation, RADIUS clients run on Cisco routers and send authentication and accounting requests to a central RADIUS server that contains all user authentication and network service access information.

RADIUS is a fully open protocol, distributed in source code format, that can be modified to work with any security system currently available on the market.

Cisco supports RADIUS under its AAA security paradigm. RADIUS can be used with other AAA security protocols, such as TACACS+, Kerberos, and local username lookup.


Note

RADIUS is supported on all Cisco platforms, but some RADIUS-supported features run only on specified platforms.

RADIUS has been implemented in a variety of network environments that require high levels of security while maintaining network access for remote users.

Use RADIUS in the following network environments that require access security:

  • Networks with multiple-vendor access servers, each supporting RADIUS. For example, access servers from several vendors use a single RADIUS server-based security database. In an IP-based network with multiple vendors’ access servers, dial-in users are authenticated through a RADIUS server that has been customized to work with the Kerberos security system.

  • Turnkey network security environments in which applications support the RADIUS protocol, such as in an access environment that uses a “smart card” access control system. In one case, RADIUS has been used with Enigma security cards to validate users and grant access to network resources.

  • Networks already using RADIUS. You can add a Cisco router with RADIUS to the network. This might be the first step when you make a transition to a Terminal Access Controller Access Control System Plus (TACACS+) server.

  • Networks in which a user must access only a single service. Using RADIUS, you can control user access to a single host, utility such as Telnet, or protocol such as Point-to-Point Protocol (PPP). For example, when a user logs in, RADIUS identifies this user as having authorization to run PPP using IP address 10.2.3.4 and the defined access list is started.

  • Networks that require resource accounting. You can use RADIUS accounting independent of RADIUS authentication or authorization. The RADIUS accounting functions allow data to be sent at the start and end of services, indicating the amount of resources (such as time, packets, bytes, and so on) used during the session. An Internet service provider (ISP) might use a freeware-based version of RADIUS access control and accounting software to meet special security and billing needs.

  • Networks that support preauthentication. Using the RADIUS server in your network, you can configure AAA preauthentication and set up the preauthentication profiles. Preauthentication enables service providers to better manage ports using their existing RADIUS solutions and to efficiently manage the use of shared resources to offer differing service-level agreements.

Network Security Situations in Which RADIUS is Unsuitable

RADIUS is not suitable in the following network security situations:

  • Multiprotocol access environments. RADIUS does not support the following protocols:

    • NetBIOS Frame Control Protocol (NBFCP)

    • NetWare Asynchronous Services Interface (NASI)

    • X.25 PAD connections

  • Router-to-router situations. RADIUS does not provide two-way authentication. RADIUS can be used to authenticate from one router to a router other than a Cisco router if that router requires RADIUS authentication.

  • Networks using a variety of services. RADIUS generally binds a user to one service model.

RADIUS Operation

When a user attempts to log in and authenticate to an access server using RADIUS, the following steps occur:

  1. The user is prompted for and enters a username and password.

  2. The username and encrypted password are sent over the network to the RADIUS server.

  3. The user receives one of the following responses from the RADIUS server:

    1. ACCEPT—The user is authenticated.

    1. REJECT—The user is not authenticated and is prompted to reenter the username and password, or access is denied.

    1. CHALLENGE—A challenge is issued by the RADIUS server. The challenge collects additional data from the user.

    1. CHANGE PASSWORD—A request is issued by the RADIUS server, asking the user to select a new password.

    The ACCEPT or REJECT response is bundled with additional data used for XR EXEC mode or network authorization. You must first complete RADIUS authentication before using RADIUS authorization. The additional data included with the ACCEPT or REJECT packets consists of the following:

  • Services that the user can access, including Telnet, rlogin, or local-area transport (LAT) connections, and PPP, Serial Line Internet Protocol (SLIP), or XR EXEC mode services.

  • Connection parameters, including the host or client IP address, access list, and user timeouts.