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:
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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.
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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. |
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
taskgroup taskgroup-name Example:Creates a name for a particular task group and enters task group configuration submode.
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| Step 3 |
description string Example:(Optional) Creates a description of the task group named in Step 2. |
| Step 4 |
task {read | write | execute | debug} taskid-name Example:Specifies a task ID to be associated with the task group named in Step 2.
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| Step 5 |
Repeat for each task ID to be associated with the task group named in Step 2. |
| Step 6 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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. |
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
usergroup usergroup-name Example:Creates a name for a particular user group and enters user group configuration submode.
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| Step 3 |
description string Example:(Optional) Creates a description of the user group named in Step 2. |
| Step 4 |
inherit usergroup usergroup-name Example:
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| Step 5 |
taskgroup taskgroup-name Example:Associates the user group named in Step 2 with the task group named in this step.
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| Step 6 |
Repeat Step for each task group to be associated with the user group named in Step 2. |
| Step 7 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
username user-name Example:Creates a name for a new user (or identifies a current user) and enters username configuration submode.
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| Step 3 |
Do one of the following:
Example:or Specifies a password for the user named in step 2.
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| Step 4 |
group group-name Example:Assigns the user named in step 2 to a user group that has already been defined through the usergroup command.
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| Step 5 |
Repeat step 4 for each user group to be associated with the user specified in step 2. |
| Step 6 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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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:
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Hostname or IP address
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Authentication destination port
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Accounting destination port
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Retransmission value
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Timeout period
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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. |
Procedure
| Step 1 |
configure Example:Enters mode. |
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| Step 2 |
radius-server host {hostname | ip-address} [auth-port port-number] [acct-port port-number] [timeout seconds] [retransmit retries] [key string] Example:Specifies the hostname or IP address of the remote RADIUS server host.
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| Step 3 |
radius-server retransmit retries Example:Specifies the number of times the software searches the list of RADIUS server hosts before giving up.
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| Step 4 |
radius-server timeout seconds Example:Sets the number of seconds a router waits for a server host to reply before timing out.
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| Step 5 |
radius-server key {0 clear-text-key | 7 encrypted-key | clear-text-key} Example:Sets the authentication and encryption key for all RADIUS communications between the router and the RADIUS daemon. |
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| Step 6 |
radius source-interface type instance [vrf vrf-id] Example:(Optional) Forces RADIUS to use the IP address of a specified interface or subinterface for all outgoing RADIUS packets.
The vrf keyword enables the specification on a per-VRF basis. |
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| Step 7 |
Repeat step 2 through step 6 for each external server to be configured. |
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| Step 8 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| Step 9 |
show radius Example:(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
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
radius-server deadtime minutes Example: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: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:Establishes the number of tries for the dead-criteria conditions for a RADIUS server to be marked as dead. |
| Step 5 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| Step 6 |
show radius dead-criteria host ip-addr [auth-port auth-port] [acct-port acct-port] Example:(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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
tacacs-server host host-name port port-number Example:Specifies a TACACS+ host server and optionally specifies a server port number.
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| Step 3 |
tacacs-server host host-name timeout seconds Example: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.
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| Step 4 |
tacacs-server host host-name key [0 | 7] auth-key Example:Specifies a TACACS+ host server and optionally specifies an authentication and encryption key shared between the AAA server and the TACACS+ server.
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| Step 5 |
tacacs-server host host-name single-connection Example: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:(Optional) Specifies the source IP address of a selected interface for all outgoing TACACS+ packets.
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| Step 7 |
Repeat step 2 through step 5 for each external server to be configured. |
| Step 8 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| Step 9 |
show tacacs Example:(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 consoleConfigure 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.
Procedure
| Step 1 |
configure Example:Enters mode. |
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| Step 2 |
aaa group server radius group-name Example:Groups different server hosts into distinct lists and enters the server group configuration mode. |
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| Step 3 |
server {hostname | ip-address} [auth-port port-number] [acct-port port-number] Example:Specifies the hostname or IP address of an external RADIUS server.
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| Step 4 |
Repeat step 4 for every external server to be added to the server group named in step 3. |
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| Step 5 |
deadtime minutes Example:Configures the deadtime value at the RADIUS server group level.
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
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| Step 6 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| Step 7 |
show radius server-groups [group-name [detail]] Example:(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 section).
Procedure
| Step 1 |
configure Example:Enters mode. |
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| Step 2 |
aaa group server tacacs+ group-name Example:Groups different server hosts into distinct lists and enters the server group configuration mode. |
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| Step 3 |
server {hostname | ip-address} Example:Specifies the hostname or IP address of an external TACACS+ server.
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| Step 4 |
Repeat step 3 for every external server to be added to the server group named in step 2. |
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| Step 5 |
server-private {hostname | ip-address in IPv4 or IPv6 format} [port port-number] [timeout seconds] [key string] Example:Configures the IP address of the private TACACS+ server for the group server.
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| Step 6 |
(Optional) vrf vrf-id Example:The vrf option specifies the Virtual Private Network (VPN) routing and forwarding (VRF) reference of an AAA TACACS+ server group. |
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| Step 7 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| Step 8 |
show tacacs server-groups Example:(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:
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Be familiar with configuring TACACS+, AAA, per VRF AAA, and group servers.
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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
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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. |
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
aaa authentication {login} {default | list-name} method-list Example:Creates a series of authentication methods, or a method list.
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| Step 3 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
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| 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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
aaa authorization {commands | eventmanager | exec | network} {default | list-name} {none | local | group {tacacs+ | radius | group-name}} Example:Creates a series of authorization methods, or a method list.
|
| Step 3 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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.
Procedure
| Step 1 |
configure Example:Enters mode. |
||
| Step 2 |
Do one of the following:
Example:
Creates a series of accounting methods, or a method list.
|
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| Step 3 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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. |
Procedure
| Step 1 |
configure Example:Enters mode. |
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| Step 2 |
aaa accounting update {newinfo | periodic minutes} Example:Enables periodic interim accounting records to be sent to the accounting server.
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| Step 3 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
line { console | default | template template-name} Example:Enters line template configuration mode. |
| Step 3 |
authorization {commands | exec} {default | list-name} Example:Enables AAA authorization for a specific line or group of lines.
|
| Step 4 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
line { console | default | template template-name} Example:Enters line template configuration mode. |
| Step 3 |
accounting {commands | exec} {default | list-name} Example:Enables AAA accounting for a specific line or group of lines.
|
| Step 4 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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.
Procedure
| Step 1 |
configure Example:Enters mode. |
| Step 2 |
line template template-name Example:Specifies a line to configure and enters line template configuration mode. |
| Step 3 |
timeout login response seconds Example:Sets the interval that the server waits for reply to a login.
|
| Step 4 |
Use the commit or end command. commit —Saves the configuration changes and remains within the configuration session.
|
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:
Procedure
| 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: |
| 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: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 to display all the tasks user1 can perform. For example: Example: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: |
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. |
|
|
Admin-r/w/x/d |
Admin-r |
Read only commands on Sysadmin VM |
|
|
Netadmin or sysadmin group Admin-r/ wx /d, aaa -r/w/x/d |
Aaa -r and admin -r |
Read only commands on Sysadmin VM |
|
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 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 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 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 ).
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:
-
A user requests authentication by providing a username and password (or secret).
-
AAA verifies the user’s password and rejects the user if the password does not match what is in the database.
-
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 and external API clients can use this feature to optimize their operations. 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. |
|
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/# 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:
-
The user is prompted for and enters a username and password.
-
The username and encrypted password are sent over the network to the RADIUS server.
-
The user receives one of the following responses from the RADIUS server:
-
ACCEPT—The user is authenticated.
-
REJECT—The user is not authenticated and is prompted to reenter the username and password, or access is denied.
-
CHALLENGE—A challenge is issued by the RADIUS server. The challenge collects additional data from the user.
-
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 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 services.
-
Connection parameters, including the host or client IP address, access list, and user timeouts.
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