Getting Started

Initial StarOS Configuration

Following successful installation of VPC-DI across all VMs, you must configure a set of StarOS parameters via the active Control Function (CF) VM. You then save these settings in a configuration file on the active CF that is accessed whenever a VM in the VPC-DI instance is rebooted. The standby CF and all Service Function (SF) VMs read this configuration file from the active CF.

This chapter provides instructions for connecting to the active CF console port and creating the initial local context management configuration.

Using the StarOS CLI for Initial Configuration

The initial configuration consists of the following:

  • Configuring a context-level security administrator and hostname

  • Configuring the Ethernet interface on the vNIC

  • Configuring the VPC-DI instance for remote CLI access via SSH

This section provides instructions for performing these tasks using the CLI.

Procedure

Step 1

Log into the Console port of the active CF VM via the hypervisor.

Step 2

At the CLI prompt, enter: 

[local]cf_host_name configure [local]cf_host_name (config)
Step 3

Enter the context configuration mode by entering the following command: 

[local]cf_host_name(config) context local [local]cf_host_name (config-ctx)
The local context is the VPC-DI instance\'s management context. Contexts allow you to logically group services or interfaces. A single context can consist of multiple services and can be bound to multiple interfaces.
Step 4

Enter the following command to configure a context-level security administrator for the VPC-DI instance: 


administrator user_name [ encrypted ] password password 
| [ ecs ] [ expiry-date date_time ] [ ftp ] [ li-administration ] [ nocli ] [ noecs ] 
   
  ]
Note 

You must configure a context-level security administrator during the initial configuration. After you complete the initial configuration process and end the CLI session, if you have not configured a security administrator, CLI access will be locked. See the Context Configuration Mode Commands chapter in the Command Line Interface Reference for complete information about this command.

Step 5

Enter the following command at the prompt to exit the context configuration mode: 

[local]cf_host_name(config-ctx) exit 
[local]cf_host_name(config)
Step 6

Enter the following command to configure a hostname by which the VPC-DI instance will be recognized on the network: 

[local]cf_host_name(config) system hostname cf_host_name
cf_host_name is the name by which the VPC-DI instance will be recognized on the network. The hostname is an alphanumeric string of 1 through 63 characters that is case sensitive. The default hostname is "qvpc-di".
Step 7

Configure the network interfaces on the vNIC as follows:

  1. Enter the context configuration mode by entering the following commands: 

    [local]cf_host_name(config) context local 
[local]cf_host_name(config-ctx)

  2. Enter the following command to specify a name for the interface: 

    [local]cf_host_name(config-ctx) interface interface_name
    interface_name is the name of the interface expressed as an alphanumeric string of 1 through 79 characters that is case sensitive. The following prompt appears as StarOS enters the Ethernet Interface Configuration mode: 
    [local]cf_host_name(config-if-eth)

  3. Configure an IP address for the interface configured in the previous step by entering the following command: 

    { ip address | ipv6 address } ipaddress subnetmask
    Note 

    If you are executing this command to correct an address or subnet that was mis-configured with the Quick Setup Wizard, you must verify the default route and port binding configuration. Use step 11 and step 6 of this procedure. If there are issues, perform steps 7e through 7k to reconfigure the information.

  4. Enter the following command to exit the Ethernet interface configuration mode: 

    [local]cf_host_name(config-if-eth) exit 
[local]cf_host_name(config-ctx)

  5. Configure a static route, if required, to point the VPC-DI instance to a default gateway. Entering the following command: 

    { ip | ipv6 } route gw_address interface_name

  6. Enter the following to exit from the context configuration mode: 

    [local]cf_host_name(config-ctx) exit 
[local]cf_host_name(config)

  7. Enter the Ethernet Port Configuration mode: 

    [local]cf_host_name(config) port ethernet slot/port
    For VPC-DI, the slot corresponds to a CF or SF VM within the virtual chassis. The hypervisor assigns a unique slot number to each VM during initial configuration of the VPC-DI instance. Slots 1 and 2 are assigned to the CF VMs; slot numbers 3 through 32 are assigned to SF VMs. The CF only supports port 1. Each SF supports four vNICs numbered 1 through 4 with corresponding virtual ethernet ports numbered 10 through 14. SF port number 10 must be configured.

  8. Bind the port to the interface that you created in step 7b. Binding associates the port and all of its settings to the interface. Enter the following command: 

    [local]cf_host_name(config-port-slot/port) bind interface interface_name local 
[local]cf_host_name(config-port-slot/port) no shutdown
    interface_name is the name of the interface that you configured in step 7b.

  9. Exit the Ethernet Interface Configuration mode by entering the command: 

    [local]cf_host_name(config-port-slot/port) exit 
[local]cf_host_name(config)
    Note 

    The management port also supports VLANs. For additional information, refer to the VLANs section of the Interfaces and Ports chapter.

Configuring System Administrative Users

This section describes some of the security features that allow security administrators to control user accounts.

Limiting the Number of Concurrent CLI Sessions

Security administrators can limit the number of concurrent interactive CLI sessions. Limiting the number of concurrent interactive sessions reduces the consumption of system-wide resources. It also prevents a user from potentially accessing sensitive user in formation which is already in use.

Most privileged accounts do not require multiple concurrent logins.

Note
In 21.9 and later releases, multiple channels in a single CLI session is not supported.

Important

Configuring the maximum number of sessions is recommended for all privileged accounts.

Security administrators can limit the number of concurrent interactive CLI sessions with three different ways depending on the authentication method which his used for that particular user account.

StarOS supports three login authentication methods:

  • TACACS+ Server users
  • Local-User users
  • AAA Context users

For additional information on configuring the maximum number of sessions for TACACS+ Server users, see Operation. For additional information on configuring the maximum number of sessions for Local-User users and AAA context users, see Configuring Context-Level Administrative Users.

Each authentication method must be configured separately because each of the three authentication methods can use the same user name.

Automatic Logout of CLI Sessions

Security administrators can configure an automatic logout of certain user accounts. Limiting the number of minutes that an interactive CLI session can be in use reduces the consumption of system-wide resources. It also prevents a user from potentially accessing a user account in a terminal window which is left idle. All authentication methods described in this section support both the idle session timeout technique and the absolute session timeout technique.

Most privileged accounts do not require an indefinite login timeout limit.


Important

Configuring the session timeout is strongly recommended for all privileged accounts.

The idle timeout and session timeout fields in the show tacacs summary and show tacacs session id commands allow administrators to configure an automatic logout of certain accounts.

Session Timeout: allows a security administrator to specify the maximum amount of minutes that a user can be logged in to a session before the session is automatically disconnected.

Idle Timeout: allows a security administrator to specify the maximum amount of minutes that a session can remain in an idle state before the session is automatically disconnected.


Important

The session timeout and idle timeout fields are not exclusive. If both are specified, then the idle timeout should always be lower than the session timeout since a lower session timeout will always be reached first.

For additional information on configuring the maximum number of minutes that an interactive CLI session can be in use, see the idle-sessions threshold command and the clear tacacs sessions CLI command in the CLI Reference and the show tacacs summary and show tacacs session id in the Statistics and Counter Reference.

Configuring the System for Remote Access

Configure the system for remote access. An administrative user may access the instance from a remote location over the management network:

  • Telnet

  • Secure Shell (SSH)

  • File Transfer Protocol (FTP) (secured or unsecured)

  • Trivial File Transfer Protocol (TFTP)


Note

If there are two simultaneous telnet sessions, and one administrator deletes the context into which the other administrator is logged, the administrator in the deleted context will not be automatically kicked into the local context. Although the deleted context will still appear in the CLI prompt, context specific commands will generate errors.


Note

For maximum security, use SSH v2.

Procedure

Step 1

Enter the context configuration mode by entering the following command: 

[local]cf_host_name(config) context local 
[local]cf_host_name(config-ctx)
Step 2

Configure the system to allow Telnet access, if desired: 

[local]cf_host_name(config-ctx) server telnetd
Step 3

Configure the system to allow SSH access, if desired: 

[local]cf_host_name(config-ctx) ssh generate key [ type v2-rsa ]
Note 

v2-rsa is the recommended key type.

Note 

In Release 4.0 and higher, the v1-rsa keyword has been removed and the v2-dsa keyword has been concealed within the Context Configuration mode ssh generate CLI command. A keyword that was supported in a previous release may be concealed in subsequent releases. The system continues to parse concealed keywords in existing scripts and configuration files created in a previous release. But the concealed keyword no longer appears in the command syntax for use in new scripts or configuration files. Entering a question mark (?) will not display a concealed keyword as part of the Help text. A removed keyword generates an error message when parsed. 

[local]cf_host_name(config-ctx) server sshd 
[local]cf_host_name(config-sshd) subsystem sftp 
[local]cf_host_name(config-sshd) exit
Step 4

Configure the system to allow FTP access, if desired, by entering the following command: 

[local]cf_host_name(config-ctx) server ftpd
Step 5

Exit the configuration mode by entering the following command: 

[local]cf_host_name(config-ctx) end 
[local]cf_host_name
Step 6

Verify the configuration by entering the following command: 

[local]cf_host_name show configuration
The CLI output should be similar to the sample output: 
context local 
   interface interface_name 
      ip address ipaddress subnetmask 
      exit 
   subscriber default 
      exit 
   administrator admin_name password admin_password 
   server telnetd 
   server ftpd 
   ssh generate key 
   server sshd 
   subsystem sftp 
   exit 
port ethernet 1/1 
   bind interface interface_name local 
   exit 
port ethernet 1/1 
   no shutdown 
   exit 
 snmp engine-id local 800007e580ed826c191ded2d3d 
end
Step 7

Verify the configuration of the IP routes by entering the following command: 

[local]cf_host_name show ip route
The CLI output should be similar to the sample output: 
"*" indicates the Best or Used route. 
 Destination         Nexthop         Protocol  Prec Cost Interface 
*0.0.0.0/0           ipaddress      static     1    0    vnic1 
*network            0.0.0.0         connected  0    0    vnic1
Step 8

Verify the interface binding by entering the following command: 

[local]cf_host_name show ip interface name interface_name
interface_name is the name of the interface that was configured in step 7b.The CLI output should be similar to the sample output: 
Intf Name:       vnic1 

Description: 
IP State:        UP (Bound to 1/1 untagged, ifIndex 83951617) 
IP Address:      ipaddress          Subnet Mask:     subnetmask 
Bcast Address:   bcastaddress       MTU:             1500 
Resoln Type:     ARP                ARP timeout:     3600 secs L3 monitor LC-port
switchover: DiasabledNumber of Secondary Addresses:  0
Step 9

Save your configuration as described in the Verifying and Saving Your Configuration chapter.

Configuring SSH Options

SSHv2 RSA is the only version of SSH supported under StarOS. Keywords previously supported for SSHv1 RSA and SSHv2 DSA have been removed from or concealed within the StarOS CLI.


Important

A keyword that was supported in a previous release may be concealed in subsequent releases. StarOS continues to parse concealed keywords in existing scripts and configuration files created in a previous release. But the concealed keyword no longer appears in the command syntax for use in new scripts or configuration files. Entering a question mark (?) will not display a concealed keyword as part of the Help text. Removed keywords generate an error message when parsed.

Version 1 of the SSH protocol is now obsolete due to security vulnerabilities. The v1-rsa keyword has been removed for the Context Configuration mode ssh command. Running a script or configuration that uses the SSHv1-RSA key returns an error message and generates an event log. The output of the error message is shown below: 

CLI print failure Failure: SSH V1 contains multiple structural vulnerabilities and is no longer considered secure. Therefore we don't support v1-rsa SSH key any longer, please generate a new v2-rsa key to replace this old one.

If the system boots from a configuration that contains the v1-rsa key, you can expect a boot failure when logging in through SSH. The workaround is to log in via the Console port, re-generate a new ssh v2-rsa key, and configure server sshd. It will then be possible to log in via ssh.

The v2-dsa keyword is now concealed for the Context Configuration mode ssh command

The v1-rsa keyword has been removed from the Exec mode show ssh key CLI command.

SSH Host Keys

SSH key-based authentication uses two keys, one "public" key that anyone is allowed to see, and another "private" key that only the owner is allowed to see. You create a key pair, securely store the private key on the device you want to log in from, and store the public key on the system (VPC-DI) that you wish to log into.

SSH host keys are generated within a specified StarOS context. The context is associated with a user interface.

You set or remove an administrative user name having authorized keys for access to the sshd server associated with context.

Setting SSH Key Size

The Global Configuration mode ssh key-size CLI command configures the key size for SSH key generation for all contexts (RSA host key only).

Procedure
Step 1

Enter the Global Configuration mode. 

[local]host_name# configure 
[local]host_name(config)#
Step 2

Specify the bit size for SSH keys. 

[local]host_name(config)# ssh key-size { 2048 | 3072 | 4096 | 5120 | 6144 | 7168 | 9216 }
The default bit size for SSH keys is 2048 bits.

Configuring SSH Key Generation Wait Time

SSH keys can only be generated after a configurable time interval has expired since the last key generation. The ssh key-gen wait-time command specifies this wait time in seconds. The default interval is 300 seconds (5 minutes).

Procedure
Step 1

Enter the context configuration mode. 

[local]host_name(config)# context context_name 
[local]host_name(config-ctx)#
Step 2

Specify the wait time interval. 

[local]host_name(config-ctx)# ssh key-gen wait-time seconds 
[local]host_name(config-ctx)#

Notes:

  • seconds is specified as an integer from 0 through 86400. Default = 300

Specifying SSH Encryption Ciphers

The SSH Configuration mode ciphers CLI command configures the cipher priority list in sshd for SSH symmetric encryption. It changes the cipher options for that context.

Procedure
Step 1

Enter the SSH Configuration mode. 

[local]host_name(config-ctx)# server sshd
Step 2

Specify the desired encryption algorithms. 

[local]host_name(config-sshd)# ciphers algorithms
Notes:
  • algorithms is a string of 1 through 511 alphanumeric characters that specifies the algorithm(s) to be used as a single string of comma-separated variables (no spaces) in priority order (left to right) from those shown below:
    • blowfish-cbc – symmetric-key block cipher, Cipher Block Chaining, (CBC)
    • 3des-cbc – Triple Data Encryption Standard, CBC
    • aes128-cbc – Advanced Encryption Standard (AES), 128-bit key size, CBC
    • aes128-ctr – AES, 128-bit key size, Counter-mode encryption (CTR)
    • aes192-ctr – AES, 192-bit key size, CTR
    • aes256-ctr – AES, 256-bit key size, CTR
    • aes128-gcm@openssh.com – AES, 128-bit key size, Galois Counter Mode [GCM], OpenSSH
    • aes256-gcm@openssh.com – AES, 256-bit key size, GCM, OpenSSH
    • chacha20-poly1305@openssh.com – ChaCha20 symmetric cipher, Poly1305 cryptographic Message Authentication Code [MAC], OpenSSH

The default string for algorithms in a Normal build is: 

blowfish-cbc,3des-cbc,aes128-cbc,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,
chacha20-poly1305@openssh.com

The default string for algorithms in a Trusted build is: 

aes256-ctr,aes192-ctr,aes128-ctr
Step 3

Exit the SSH Configuration mode. 

[local]host_name(config-sshd)# end 
[local]host_name#

MAC Algorithm Configuration

Feature Summary and Revision History
Summary Data

Applicable Product(s) or Functional Area

All

Applicable Platform(s)

  • ASR 5500

  • VPC-DI

  • VPC-SI

Feature Default

Disabled - Configuration required

Related Changes in This Release

Not applicable

Related Documentation

  • ASR 5500 System Administration Guide

  • Command Line Interface Reference

  • VPC-DI System Administration Guide

  • VPC-SI System Administration Guide
Revision History

Important

Revision history details are not provided for features introduced before releases 21.2 and N5.1.

Revision Details

Release

First introduced.

21.13
Feature Description

The MAC Algorithm Configuration feature allows to configure or change the priority of MAC algorithms of internal SSHD servers.

A new CLI MACs CLI command is introduced in SSH Configuration Mode in support of this feature.

Configuring MAC Algorithms

This section describes how to configure the MAC alogrithims.

Use the following configuration to specify the priority of the MAC algorithms. 

configure 
   context context_name 
      server sshd 
         macs algorithms 
         end 
default macs

NOTES:

  • algorithms: Refers to a string of 1 through 511 alphanumeric characters that specifies the algorithms to be used as a single string of comma-separated variables (no spaces) in priority order (left to right) from those listed as follows:

    • HMAC = hash-based message authentication code

    • SHA2 = Secure Hash Algorithm 2

    • SHA1 = Secure Hash Algorithm 1

    • ETM = Encrypt-Then-MAC

    • UMAC = message authentication code based on universal hashing

  • The help string and list of algorithms in a Normal build are:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1,umac-128-etm@openssh.com,umac-128@openssh.com,umac-64-etm@openssh.com,umac-64@openssh.com

  • The help string and list of algorithms in a Trusted build are:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1

  • The default value string is:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1
Specifying MAC Algorithms

Use the following CLI commands to configure the priority of MAC algorithms. This command is configured in in SSH Configuration Mode. 

configure 
   context context_name 
      server sshd 
         macs algorithms 
         end 
default macs

NOTES:

  • algorithms: Refers to a string of 1 through 511 alphanumeric characters that specifies the algorithms to be used as a single string of comma-separated variables (no spaces) in priority order (left to right) from those listed as follows:

    • HMAC = hash-based message authentication code

    • SHA2 = Secure Hash Algorithm 2

    • SHA1 = Secure Hash Algorithm 1

    • ETM = Encrypt-Then-MAC

    • UMAC = message authentication code based on universal hashing

  • The help string and list of algorithms in a Normal build are:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1,umac-128-etm@openssh.com,umac-128@openssh.com,umac-64-etm@openssh.com,umac-64@openssh.com

  • The help string and list of algorithms in a Trusted build are:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1

  • The default value string is:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1

Generating SSH Keys

The ssh generate command generates a public/private key pair which is to be used by the SSH server. The v1-rsa keyword has been removed from and the v2-dsa keyword concealed within the ssh generate CLI command. The only keyword available for generating SSH keys is v2-rsa.


Important

The generated key pair remains in use until the command is issued again.

Procedure
Step 1

Enter the context configuration mode: 

[local]host_name(config)# context context_name 
[local]host_name(config-ctx)#
Step 2

Generate an SSH key pair. 

[local]host_name(config-ctx)# ssh generate key type v2-rsa 
[local]host_name(config-ctx)#

Setting SSH Key Pair

The ssh key command sets the public/private key pair to be used by the system. The v2-dsa keyword is concealed in the ssh key command.

Procedure

Specify the SSH key pair parameters. 

[local]host_name(config-ctx)# ssh key data length octets type v2-rsa
Notes:
  • data is the encrypted key expressed as an alphanumeric string of 1 through 1023 characters
  • length octets is the length of the encrypted key in octets expressed as an integer from 0 through 65535
  • type specifies the key type; v2-rsa is the only supported type.
Important 

For releases prior to 20.0, StarOS supports a maximum of 64 configurable authorized SSH keys. For release 20.0 and higher, StarOS supports a maximum of 200 configurable authorized SSH keys.

Authorized SSH User Access

You must authorize users to access a StarOS context from a specific host with an SSH authentication-key pair.

Authorizing SSH User Access

The SSH Configuration mode authorized-key command grants user access to a context from a specified host.

Procedure
Step 1

Go to the SSH Configuration mode. 

[local]host_name(config-ctx)# server sshd 
[local]host_name(config-sshd)#
Step 2

Specify administrative user access via the authorized-key command. 

[local]host_name(config-sshd)# authorized-key username user_name host host_ip [ type { v2-dsa | v2-rsa } ]
Notes:
  • username user_name specifies an existing StarOS administrator user name as having authorized keys for access to the sshd server. The user_name is expressed as an alphanumeric string of 1 through 255 characters. User names should have been previously created via the Context Configuration mode administrator command using the nopassword option to prevent bypassing of the sshd keys. Refer to the System Settings chapter for additional information on creating administrators.
  • host host_ip specifies the IP address of an SSH host having the authorization keys for this username. The IP address must be in IPv4 dotted-decimal or IPv6 colon-separated-hexadecimal notation.
  • type specifies the key type; v2-rsa is the only supported type.

SSH User Login Restrictions

An administrator can restrict SSH access to the StarOS CLI to a "white list" of allowed users. Access to a service may be restricted to only those users having a legitimate need. Only explicitly allowed users will be able connect to a host via SSH. The user name may optionally include a specific source IP address.

The AllowUsers list consists of user name patterns, separated by space. If the pattern takes the form 'USER' then login is restricted for that user. If pattern is in the format 'USER@IP_ADDRESS' then USER and IP address are separately checked, restricting logins to those users from the specified IP address.

The default is to allow unrestricted access by any user.

Creating an Allowed Users List

The allowusers add command allows an administrator to create a list of users who may log into the StarOS CLI.

Procedure
Step 1

Enter the context configuration mode. 

[local]host_name(config)# context context_name 
[local]host_name(config-ctx)#
Step 2

Go to the SSH Configuration mode. 

[local]host_name(config-ctx)# server sshd
Step 3

Configure the SSH user list. 

[local]host_name(config-sshd)# allowusers add user_list

user_list specifies a list of user name patterns, separated by spaces, as an alphanumeric string of 1 through 999 characters. If the pattern takes the form 'USER' then login is restricted for that user.

If the pattern is in the format 'USER@IP_ADDRESS' then user name and IP address are separately checked, restricting logins to those users from that particular IP address.

If the pattern is in the format 'USER@<context>@IP_ADDRESS' then user name, StarOS context and IP address are separately checked, restricting logins to those users associated with the specific context from that particular IP address.

The following limits apply to the user_list:

  • The maximum length of this string is 3000 bytes including spaces.

  • The maximum number of AllowUsers, which is counted by spaces, is 256, which is consistent with the limit from OpenSSH.

Important 

If you exceed either of the above limits, an error message is displayed. The message prompts you to use a regular expression pattern to shorten the string, or remove all the allowusers with no allowusers add or default allowusers add and re-configure.

For additional information, see the SSH Configuration Mode Commands chapter in the Command Line Interface Reference.

Step 4

Exit the SSH Configuration mode. 

[local]host_name(config-sshd)# end 
[local]host_name#

SSH User Login Authentication

StarOS authenticates SSH user login attempts via authorized-key/user-account pairings for the following scenarios:

  • User tries to login with local context username through local context (VPN) interface with authorized-key configured on local context.

  • User tries to login with non-local context username through non-local context interface with authorized-key configured on non-local context.

  • User tries to login with local context username through non-local context interface with authorized-key configured on local context.

  • User tries to login with non-local context username through local context interface with authorized-key configured on non-local context.

A failure to authenticate based on the current system configuration prevents the login and generates an error message.

StarOS does not permit users with different user IDs but having the same public SSH key to login to an unauthorized context. Authentication of the user takes into account the authorized-key/user-account pairing.


Important

For StarOS release 21.0 onwards, a user cannot access the /flash directory if the user logs in from a non-local context.

Secure Session Logout

When StarOS is disconnected from an SSH client, the default behavior has sshd terminate the CLI or SFTP session in about 45 seconds (using default parameters). Two SSH Configuration mode CLI commands allow you to disable or modify this default sshd disconnect behavior.


Important

For higher security, Cisco recommends at least a client-alive-countmax of 2 and client-alive-interval of 5. Smaller session logout values may lead to occasional ssh session logouts. Adjust values to balance security and user friendliness.

The client-active-countmax command sets the number of client-alive messages which may be sent without sshd receiving any messages back from the SSH client (default =3). If this threshold is reached while the client-alive messages are being sent, sshd disconnects the SSH client thus terminating the session.

The client-alive-interval command sets a timeout interval in seconds (default = 15) after which if no data has been received from the SSH client, sshd sends a message through the encrypted channel to request a response from the client. The number of times that the message is sent is determined by the client-alive-countmax parameter. The approximate amount of time before sshd disconnects an SSH client disconnect = client-alive-countmax X client-alive-interval.

The client-alive mechanism is valuable when the client or server depend on knowing when a connection has become inactive.


Important

The client-alive messages are sent through the encrypted channel and, therefore, are not spoofable.


Important

These parameter apply to SSH protocol version 2 only.

Changing Default sshd Secure Session Logout Parameters

The following command sequence modifies the default settings for the ClientAliveCountmax (default = 3) and ClientAliveInterval (default = 15 seconds) parameters.
Procedure
Step 1

Enter the context configuration mode. 

[local]host_name# configure
Step 2

Go to the SSH Configuration mode. 

[local]host_name(config)# context context_name
Step 3

Set the ClientAliveCountmax parameter to 2. 

[local]host_name(config-sshd)# client-alive-countmax 2
Step 4

Set the ClientAliveInterval parameter to 5 seconds. 

[local]host_name(config-sshd)# client-alive-interval 5
Step 5

Exit the SSH Configuration mode. 

[local]host_name(config-sshd)# end 
[local]host_name#

SSH Client Login to External Servers

StarOS supports public key authentication for SSH/SFTP access from the StarOS gateway to external servers. You configure this feature by generating SSH client key pairs and pushing the client public key to external servers


Note

By default StarOS only supports username-password authentication to external servers.

Setting SSH Client Ciphers

The SSH Client Configuration mode ciphers CLI command configures the cipher priority list when logging into an external server.

Procedure
Step 1

Enter the SSH Client Configuration mode. 

[local]host_name(config)# client ssh
Step 2

Specify the desired encryption algorithms. 

[local]host_name(config-ssh)# ciphers algorithms
Notes:
  • algorithms is a string of 1 through 511 alphanumeric characters that specifies the algorithm(s) to be used as a single string of comma-separated variables (no spaces) in priority order (left to right) from those shown below:
    • blowfish-cbc – symmetric-key block cipher, Cipher Block Chaining, (CBC)
    • 3des-cbc – Triple Data Encryption Standard, CBC
    • aes128-cbc – Advanced Encryption Standard (AES), 128-bit key size, CBC
    • aes128-ctr – AES, 128-bit key size, Counter-mode encryption (CTR)
    • aes192-ctr – AES, 192-bit key size, CTR
    • aes256-ctr – AES, 256-bit key size, CTR
    • aes128-gcm@openssh.com – AES, 128-bit key size, Galois Counter Mode [GCM], OpenSSH
    • aes256-gcm@openssh.com – AES, 256-bit key size, GCM, OpenSSH
    • chacha20-poly1305@openssh.com – ChaCha20 symmetric cipher, Poly1305 cryptographic Message Authentication Code [MAC], OpenSSH

The default string for algorithms in a Normal build is: 

aes256-ctr,aes192-ctr,aes128-ctr,aes256-gcm@openssh.com,aes128-gcm@openssh.com,chacha20-poly1305@openssh.com, 
blowfish-cbc,3des-cbc,aes128-cbc

The default string for algorithms in a Trusted build is: 

aes256-ctr,aes192-ctr,aes128-ctr
Step 3

Exit the SSH Client Configuration mode. 

[local]host_name(config-ssh)# end 
[local]host_name#

Setting Preferred Authentication Methods

The SSH Client Configuration mode preferredauthentications CLI command configures the preferred methods of authentication.

Procedure
Step 1

Enter the SSH Client Configuration mode. 

[local]host_name(config)# client ssh
Step 2

Specify the preferred authentication methods. 

[local]host_name(config-ssh)# preferredauthentications methods
Notes:
  • methods – specifies the preferred methods of authentication to be used as a single string of comma-separated variables (no spaces) in priority order (left to right) from those shown below:

    • publickey – authentication via SSH v2-RSA protocol.

    • keyboard-interactive – request for an arbitrary number of pieces of information. For each piece of information the server sends the label of the prompt.

    • password – simple request for a single password

  • default – resets the value of methods to: publickey,password

Step 3

Exit the SSH Client Configuration mode. 

[local]host_name(config-ssh)# exit 
[local]host_name(config)#

Generating SSH Client Key Pair

You use commands in the SSH Client Configuration mode to specify a private key and generate the SSH client key pair.

Procedure
Step 1

Enter the SSH client configuration mode. 

[local]host_name(config)# client ssh 
[local]host_name(config-ssh)#
Step 2

Enter SSH private key information and key type. 

[local]host_name(config-ssh)# ssh key private_key_string length key_length [ type v2-rsa ] 
[local]host_name(config-ssh)#

key private_key_string specifies a private key value as an alphanumeric string of 1 through 4499 characters.

length key_length specifies the length of the key in bytes as an integer from 0 through 65535.

type v2-rsa specifies the SSH client key type. The only supported SSH client key type is v2-rsa.

Step 3

Generate SSH client key pair. 

[local]host_name(config-ssh)# ssh generate key [ type v2-rsa ] 
[local]host_name(config-ssh)#

type v2-rsa specifies the SSH client key type. The only supported SSH client key type is v2-rsa.

Step 4

Verify that the SSH client key has been generated. 

[local]host_name(config-ssh)# do show ssh client key
Step 5

Exit the SSH Client Configuration mode. 

[local]host_name(config-ssh)# exit 
[local]host_name(config)#

Pushing an SSH Client Public Key to an External Server

You must push the SSH client public key to an external server to support SSH/SFTP access to that server.

Procedure
Step 1

From the Exec mode run the push ssh-key command. 

[local]host_name# push ssh-key { host_name | host_ip_address } user username [ context context_name ] 
[local]host_name#

host_name specifies the remote server using its logical host name which must be resolved via DNS lookup. It is expressed as an alphanumeric string of 1 to 127 characters.

host_ip_address is expressed in IPv4 dotted-decimal or IPv6 colon-separated-hexadecimal notation.

user username specifies a valid username on the external server as an alphanumeric string of 1 to 79 characters.

context context_name specifies a valid context name. The context name is optional. If it is not provided the current context is used for processing.

Step 2

Repeat Step 1 to support SSH/SFTP access on other external servers.

Step 3

Test SSH client login to an external server. 

local]host_name# ssh { hostname | ip_address } user username port port_number

Enabling NETCONF

An SSH key is a requirement before NETCONF protocol and the ConfD engine can be enabled in support of Cisco Network Service Orchestrator (NSO).

Refer to the NETCONF and ConfD appendix in this guide for detailed information on how to enable NETCONF.

Configuring the Management Interface with a Second IP Address

If necessary, you can configure a second IP address on the vNIC management interface.

Procedure

  Command or Action Purpose
Step 1

Enter the configuration mode by entering the following command at the prompt:

 
[local]host_name configure 
[local]host_name(config)
Step 2

Enter the following to enter the context configuration mode:

 
[local]host_name(config) context local 
[local]host-name(config-ctx)
Step 3

Enter the interface slot number and port number via the following command:

 
[local]host_name(config-ctx) 1/1 
[local]host_name(config-if-eth)
Step 4

Enter the secondary IP address and subnet mask by entering the following command:

 
[local]host_name(config-if-eth) { ip | ipv } address ipaddress subnet_mask secondary
Step 5

Exit the configuration mode by entering the following command:

 
[local]host_name(config-if-eth) end
Step 6

Confirm the interface ip addresses by entering the following command:

 
[local]host_name show config context local
The CLI output should look similar to this example:
config 
   context local 
      interface interface_name 
         ip address ipaddress subnetmask 
         ip address ipaddress subnetmask secondary 
         exit
Step 7

Continue with Verifying and Saving Your Interface and Port Configuration.

Upgrade and Migration of Open SSH to Cisco SSH

Feature Summary and Revision History

Summary Data

Applicable Product(s) or Functional Area

All

Applicable Platform(s)

  • ASR 5500

  • VPC-DI

  • VPC-SI

Feature Default

Enabled - Always-on

Related Changes in This Release

Not applicable

Related Documentation

  • ASR 5500 System Administration Guide

  • Command Line Interface Reference

  • VPC-DI System Administration Guide

  • VPC-SI System Administration Guide

Revision History


Important

Revision history details are not provided for features introduced before releases 21.2 and N5.1.

Revision Details

Release

With this release, the algorithm values of Ciphers and MACs are modified based on the upgrade and migration of OpenSSH to CiscoSSH.

21.16

First introduced.

Pre 21.2

Feature Changes

As a security measure for Cisco ASR 5500 and VPC products, the Ciphers and MACs algorithm values are modified to support the upgrade and migration of the Open SSH to Cisco SSH versions.

Previous Behavior: In releases earlier to 21.16, the default algorithm values of the cipher and macs commands were as follows:

  • Cipher

    Release 20.x to 21.15 (Normal build only)

    Resets the value of algorithm in a Normal build to: 
    blowfish-cbc,3des-cbc,aes128-cbc,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com,chacha20-poly1305@openssh.com

  • MACs

    Release 20.x to 21.15 (Trusted build only)

    Resets the value of algorithm in a Trusted build to: 

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1

  • KEX Algorithms

    Release 20.x to 21.15

    Available Algorithms in Normal and Trusted Builds:

    diffie-hellman-group1-sha1,diffie-hellman-group14-sha1

New Behavior: In this release, the default algorithm values of the cipher and macs commands are as follows:

  • Cipher

    Release 21.16 onwards: Post OpenSSH to CiscoSSH Upgrade and Migration

    Default Algorithms in a Normal Build:

    aes256-ctr,aes192-ctr,aes128-ctr,aes256-gcm@openssh.com,aes128-gcm@openssh.com,chacha20-poly1305@openssh.com

    Available Algorithms in a Normal Build:

     aes256-ctr,aes192-ctr,aes128-ctr,aes256-gcm@openssh.com,aes128-gcm@openssh.com,chacha20-poly1305@openssh.com,aes128-cbc

    Default and Available Algorithms in Trusted Builds:

    aes256-ctr,aes192-ctr,aes128-ctr

    Note
    There is no change in the default and configurable Ciphers for Trusted builds.

  • MACs

    Release 21.16 onwards: Post OpenSSH to CiscoSSH Upgrade and Migration

    Default and Available Algorithms in Normal Builds:

    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com,hmac-sha2-512,
hmac-sha2-256,hmac-sha1

    Default Algorithms in Trusted Builds:

     hmac-sha2-512,hmac-sha2-256,hmac-sha1

    Available Algorithms in Trusted Builds:

    hmac-sha2-512,hmac-sha2-256,hmac-sha1

    Note
    hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,hmac-sha1-etm@openssh.com are removed from the Trusted builds.

  • KEX Algorithms

    Release 21.16 onwards: Post OpenSSH to CiscoSSH Upgrade and Migration

    Available Algorithms in Normal and Trusted Builds:

    diffie-hellman-group14-sha1

    Note
    KEX algorithms are not configurable in StarOS. Therefore, there are no CLI changes.

VM Hardware Verification

To prevent resource allocation issues, it is important that all VMs used for in the system have the same size CPU and the same size memory. To balance performance across all interfaces, make sure that the service ports and DI ports have the same throughput capabilities.

To verify the hardware configuration for all cards or a specific card, use the show cloud hardware [card_number} command. Sample output from this command on card 1 (CF) is shown here: 

[local]s1# show cloud hardware 1

Card 1:
   CPU Nodes               : 1                               
   CPU Cores/Threads       : 8                               
   Memory                  : 16384M (qvpc-di-medium)          
   Hugepage size           : 2048kB                          
   cpeth0                  :
     Driver                : virtio_net
   loeth0                  :
     Driver                : virtio_net

Sample output from this command on card 3 (SF) is shown here: 

[local]s1# show cloud hardware 1

Card 3:
   CPU Nodes               : 1                               
   CPU Cores/Threads       : 8                               
   Memory                  : 16384M (qvpc-di-medium)          
   Hugepage size           : 2048kB                          
   cpeth0                  :
     Driver                : vmxnet3
   port3_10                :
     Driver                : vmxnet3
   port3_11                :
     Driver                : vmxnet3

To display the optimum configuration of the underlying VM hardware, use the show hardware optimum . To compare your current VM configuration to the optimum configuration, use the show cloud hardware test command. Any parameters not set to the optimum are flagged with an asterisk, as shown in this sample output. In this example, the CPU cores/threads and memory are not configured optimally. 

[local]s1# show cloud hardware test 1

Card 1:
   CPU Nodes               : 1                               
*  CPU Cores/Threads       : 8                                Optimum value is 4
*  Memory                  : 8192M (qvpc-di-medium)           Optimum value is 16384
   Hugepage size           : 2048kB                          
   cpeth0                  :
     Driver                : virtio_net
   loeth0                  :
     Driver                : virtio_net

To display the configuration file on the config disk or local flash, use the show cloud configuration card_number command. The location parameter file on flash memory is defined during the installation. And the config disk is usually created by the orchestrator and then attached to the card. Sample output from this command is shown here for card 1: 

[local]s1# show cloud configuration 1

Card 1:
  Config Disk Params:
-------------------------
    No config disk available

  Local Params:
-------------------------
CARDSLOT=1
CARDTYPE=0x40010100
CPUID=0

To display the IFTASK configuration for all cards or a specific card, use the show cloud hardware iftask command. By default, the cores are configured to be used for both PMD and VNPU. Sample output from this command on card 4 is shown here: 


[local]mySystem# show cloud hardware iftask 4
Card 4:
  Total number of cores on VM:      24
  Number of cores for PMD only:     0
  Number of cores for VNPU only:    0
  Number of cores for PMD and VNPU: 3
  Number of cores for MCDMA:        4
  Hugepage size:           2048 kB
  Total hugepages:     16480256 kB
  NPUSHM hugepages:           0 kB
  CPU flags: avx sse sse2 ssse3 sse4_1 sse4_2 
  Poll CPU's: 1 2 3 4 5 6 7 
  KNI reschedule interval: 5 us