Secure Shell Commands

This module describes the Cisco IOS XR software commands used to configure Secure Shell (SSH).

For detailed information about SSH concepts, configuration tasks, and examples, see the Implementing Secure Shell on the Cisco IOS XR Software module in the System Security Configuration Guide for Cisco CRS Routers.

clear ssh

To terminate an incoming or outgoing Secure Shell (SSH) connection, use the clear ssh command in EXEC mode.

clear ssh {session-id | outgoing session-id}

Syntax Description

session-id

Session ID number of an incoming connection as displayed in the show ssh command output. Range is from 0 to 1024.

outgoing session-id

Specifies the session ID number of an outgoing connection as displayed in the show ssh command output. Range is from 1 to 10.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

Use the clear ssh command to disconnect incoming or outgoing SSH connections. Incoming connections are managed by the SSH server running on the local networking device. Outgoing connections are initiated from the local networking device.

To display the session ID for a connection, use the show ssh command.

Task ID

Task ID

Operations

crypto

execute

Examples

In the following example, the show ssh command is used to display all incoming and outgoing connections to the router. The clear ssh command is then used to terminate the incoming session with the ID number 0. 


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

SSH version: Cisco-2.0 
session     pty  location   state       userid     host        ver 
--------------------------------------------------------------------
Incoming sessions 
0           vty0 0/33/1  SESSION_OPEN   cisco   172.19.72.182   v2
1           vty1 0/33/1  SESSION_OPEN   cisco   172.18.0.5      v2
2           vty2 0/33/1  SESSION_OPEN   cisco   172.20.10.3     v1
3           vty3 0/33/1  SESSION_OPEN   cisco   3333::50        v2

Outgoing sessions 
1               0/33/1  SESSION_OPEN    cisco   172.19.72.182   v2 
2               0/33/1  SESSION_OPEN    cisco   3333::50        v2

RP/0/RP0/CPU0:router# clear ssh 0

The following output is applicable for the clear ssh command starting IOS-XR 5.3.2 releases and later. 



RP/0/RP0/CPU0:router# show ssh
SSH version : Cisco-2.0  


id  chan pty     location        state           userid    host                  ver authentication connection type
--------------------------------------------------------------------------------------------------------------------------
Incoming sessions
0   1    vty0    0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  rsa-pubkey     Command-Line-Interface 
0   2    vty1    0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  rsa-pubkey     Command-Line-Interface 
0   3            0/RSP0/CPU0     SESSION_OPEN    cisco     12.22.57.75           v2  rsa-pubkey     Sftp-Subsystem         
1        vty7    0/RSP0/CPU0     SESSION_OPEN    cisco     12.22.22.57           v1  password       Command-Line-Interface 
3   1            0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  password       Netconf-Subsystem      
4   1    vty3    0/RSP0/CPU0     SESSION_OPEN    lab       192.168.1.55          v2  password       Command-Line-Interface 

Outgoing sessions
1                0/RSP0/CPU0     SESSION_OPEN    lab       192.168.1.51          v2  password

RP/0/RP0/CPU0:router# clear ssh 0

Related Commands

Command

Description

show ssh

Displays the incoming and outgoing connections to the router.

clear netconf-yang agent session

To clear the specified netconf agent session, use the clear netconf-yang agent session in EXEC mode.

clear netconf-yang agent session session-id

Syntax Description

session-id

The session-id which needs to be cleared.

Command Default

None

Command Modes

EXEC mode

Command History

Release Modification

Release 5.3.0

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

The show netconf-yang clients command can be used to get the required session-id(s).

Task ID

Task ID Operation

config-services

read, write

Examples

This example shows how to use the clear netconf-yang agent session command: 

RP/0/RP0/CPU0:router (config) #  clear netconf-yang agent session 32125

netconf-yang agent ssh

To enable netconf agent over SSH (Secure Shell) , use the netconf-yang agent ssh command in Global Configuration mode. To disable netconf, use the no form of the command.

netconf-yang agent ssh

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release Modification

Release 5.3.0

This command was introduced.

Usage Guidelines

SSH is currently the supported transport method for Netconf.

Task ID

Task ID Operation

config-services

read, write

Examples

This example shows how to use the netconf-yang agent ssh command: 

RP/0/RP0/CPU0:router (config) #  netconf-yang agent ssh

sftp

To start the secure FTP (SFTP) client, use the sftp command in EXEC mode.

sftp [username @ host : remote-filenam e] source-filename dest-filename [source-interface type interface-path-id] [vrf vrf-name]

Syntax Description

username

(Optional) Name of the user performing the file transfer. The at symbol (@) following the username is required.

hostname:remote-filenam e

(Optional) Name of the Secure Shell File Transfer Protocol (SFTP) server. The colon (:) following the hostname is required.

source-filename

SFTP source, including the path.

dest-filename

SFTP destination, including the path.

source-interface

(Optional) Specifies the source IP address of a selected interface for all outgoing SSH connections.

type

Interface type. For more information, use the question mark (? ) online help function.

interface-path-id

Physical interface or virtual interface.

Note 

Use the show interfaces command in EXEC mode to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark (? ) online help function.

vrf vrf-name

Specifies the name of the VRF associated with the source interface.

Command Default

If no username argument is provided, the login name on the router is used. If no hostname argument is provided, the file is considered local.

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

The srcfile keyword was removed and was replaced by an argument for this same purpose.

Support was added for the vrf and the source-interface keywords.

Usage Guidelines

SFTP provides for the secure (and authenticated) copying of files between a router and a remote host. Like the copy command, the sftp command can be invoked only in EXEC mode.

If a username is not provided, the login name on the router is used as the default. If a host name is not provided, the file is considered local.

If the source interface is specified in the sftp command, the sftp interface takes precedence over the interface specified in the ssh client source-interface command.

When the file destination is a local path, all of the source files should be on remote hosts, and vice versa.

When multiple source files exist, the destination should be a preexisting directory. Otherwise, the destination can be either a directory name or destination filename. The file source cannot be a directory name.

If you download files from different remote hosts, that is, the source points to different remote hosts, the SFTP client spawns SSH instances for each host, which may result in multiple prompts for user authentication.

Task ID

Task ID

Operations

crypto

execute

basic-services

execute

Examples

In the following example, user abc is downloading the file ssh.diff from the SFTP server ena-view1 to disk0: 


RP/0/RP0/CPU0:router#sftp abc@ena-view1:ssh.diff disk0

In the following example, user abc is uploading multiple files from disk 0:/sam_* to /users/abc/ on a remote SFTP server called ena-view1: 


RP/0/RP0/CPU0:router# sftp disk0:/sam_* abc@ena-view1:/users/abc/

In the following example, user admin is downloading the file run from disk0a: to disk0:/v6copy on a local SFTP server using an IPv6 address: 



RP/0/RP0/CPU0:router#sftp admin@[2:2:2::2]:disk0a:/run disk0:/V6copy
Connecting to 2:2:2::2...
Password: 

disk0a:/run
  Transferred 308413 Bytes
  308413 bytes copied in 0 sec (338172)bytes/sec

RP/0/RP0/CPU0:router#dir disk0:/V6copy

Directory of disk0:

70144       -rwx  308413      Sun Oct 16 23:06:52 2011  V6copy

2102657024 bytes total (1537638400 bytes free)

In the following example, user admin is uploading the file v6copy from disk0: to disk0a:/v6back on a local SFTP server using an IPv6 address: 


RP/0/RP0/CPU0:router#sftp disk0:/V6copy admin@[2:2:2::2]:disk0a:/v6back 
Connecting to 2:2:2::2...
Password: 

/disk0:/V6copy
  Transferred 308413 Bytes
  308413 bytes copied in 0 sec (421329)bytes/sec

RP/0/RP0/CPU0:router#dir disk0a:/v6back

Directory of disk0a:

66016       -rwx  308413      Sun Oct 16 23:07:28 2011  v6back

2102788096 bytes total (2098987008 bytes free)

In the following example, user admin is downloading the file sampfile from disk0: to disk0a:/sampfile_v4 on a local SFTP server using an IPv4 address: 


RP/0/RP0/CPU0:router#sftp admin@2.2.2.2:disk0:/sampfile disk0a:/sampfile_v4
Connecting to 2.2.2.2...
Password:

disk0:/sampfile
  Transferred 986 Bytes
  986 bytes copied in 0 sec (493000)bytes/sec

RP/0/RP0/CPU0:router#dir disk0a:/sampfile_v4

Directory of disk0a:

131520      -rwx  986         Tue Oct 18 05:37:00 2011  sampfile_v4

502710272 bytes total (502001664 bytes free)

In the following example, user admin is uploading the file sampfile_v4 from disk0a: to disk0:/sampfile_back on a local SFTP server using an IPv4 address: 


RP/0/RP0/CPU0:router#sftp disk0a:/sampfile_v4 admin@2.2.2.2:disk0:/sampfile_back
Connecting to 2.2.2.2...
Password:

disk0a:/sampfile_v4
  Transferred 986 Bytes
  986 bytes copied in 0 sec (564000)bytes/sec

RP/0/RP0/CPU0:router#dir disk0:/sampfile_back

Directory of disk0:

121765      -rwx  986         Tue Oct 18 05:39:00 2011  sampfile_back

524501272 bytes total (512507614 bytes free)

Related Commands

Command

Description

ssh client source-interface

Specifies the source IP address of a selected interface for all outgoing SSH connections.

ssh client vrf

Configures a new VRF for use by the SSH client.

sftp (Interactive Mode)

To enable users to start the secure FTP (SFTP) client, use the sftp command in EXEC mode.

sftp [username @ host : remote-filenam e] [source-interface type interface-path-id] [vrf vrf-name]

Syntax Description

username

(Optional) Name of the user performing the file transfer. The at symbol (@) following the username is required.

hostname:remote-filenam e

(Optional) Name of the Secure Shell File Transfer Protocol (SFTP) server. The colon (:) following the hostname is required.

source-interface

(Optional) Specifies the source IP address of a selected interface for all outgoing SSH connections.

type

Interface type. For more information, use the question mark (? ) online help function.

interface-path-id

Physical interface or virtual interface.

Note 

Use the show interfaces command in EXEC mode to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark (? ) online help function.

vrf vrf-name

Specifies the name of the VRF associated with the source interface.

Command Default

If no username argument is provided, the login name on the router is used. If no hostname argument is provided, the file is considered local.

Command Modes

EXEC mode

Command History

Release

Modification

Release 3.9.0

This command was introduced.

Usage Guidelines

The SFTP client, in the interactive mode, creates a secure SSH channel where the user can enter any supported command. When a user starts the SFTP client in an interactive mode, the SFTP client process creates a secure SSH channel and opens an editor where user can enter any supported command.

More than one request can be sent to the SFTP server to execute the commands. While there is no limit on the number of 'non-acknowledged' or outstanding requests to the server, the server might buffer or queue these requests for convenience. Therefore, there might be a logical sequence to the order of requests.

The following unix based commands are supported in the interactive mode:

  • bye

  • cd <path>

  • chmod <mode> <path>

  • exit

  • get <remote-path> [local-path]

  • help

  • ls [-alt] [path]

  • mkdir <path>

  • put <local-path> [remote-path]

  • pwd

  • quit

  • rename <old-path> <new-path>

  • rmdir <path>

  • rm <path>

The following commands are not supported:

  • lcd, lls, lpwd, lumask, lmkdir

  • ln, symlink

  • chgrp, chown

  • !, !command

  • ?

  • mget, mput

Task ID

Task ID

Operations

crypto

execute

basic-services

execute

Examples

In the following example, user admin is downloading and uploading a file from/to an external SFTP server using an IPv6 address: 



RP/0/RP0/CPU0:router#sftp admin@[2:2:2::2]                                                  
Connecting to 2:2:2::2...
Password: 
sftp> pwd
Remote working directory: /
sftp> cd /auto/tftp-server1-users5/admin 
sftp> get frmRouter /disk0:/frmRouterdownoad 

/auto/tftp-server1-users5/admin/frmRouter
  Transferred 1578 Bytes
  1578 bytes copied in 0 sec (27684)bytes/sec
sftp> put /disk0:/frmRouterdownoad againtoServer

/disk0:/frmRouterdownoad
  Transferred 1578 Bytes
  1578 bytes copied in 0 sec (14747)bytes/sec
sftp>

In the following example, user abc is downloading and uploading a file from/to an external SFTP server using an IPv4 address: 



RP/0/RP0/CPU0:router#sftp abc@2.2.2.2                                                  
Connecting to 2.2.2.2...
Password: 
sftp> pwd
Remote working directory: /
sftp> cd /auto/tftp-server1-users5/abc 
sftp> get frmRouter /disk0:/frmRouterdownoad 

/auto/tftp-server1-users5/abc/frmRouter
  Transferred 1578 Bytes
  1578 bytes copied in 0 sec (27684)bytes/sec
sftp> put /disk0:/frmRouterdownoad againtoServer

/disk0:/frmRouterdownoad
  Transferred 1578 Bytes
  1578 bytes copied in 0 sec (14747)bytes/sec
sftp>

Related Commands

Command

Description

ssh client source-interface

Specifies the source IP address of a selected interface for all outgoing SSH connections.

ssh client vrf

Configures a new VRF for use by the SSH client.

show netconf-yang clients

To display the client details for netconf-yang, use the show netconf-yang clients command in EXEC mode.

show netconf-yang clients

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release Modification

Release 5.3.0

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID Operation

config-services

read

Examples

This example shows how to use the show netconf-yang clients command: 

RP/0/RP0/CPU0:router (config) #  sh netconf-yang clients
Netconf clients 
client session ID|   NC version|    client connect time|        last OP time|        last OP type|    <lock>|
 22969|          											1.1|        	 0d  0h  0m  2s|            11:11:24|       close-session|        No|           
 15389|          											1.1|        	 0d  0h  0m  1s|            11:11:25|          get-config|        No|
Table 1. Field descriptions

Field name

Description

Client session ID

Assigned session identifier

NC version

Version of the Netconf client as advertised in the hello message

Client connection time

Time elapsed since the client was connected

Last OP time

Last operation time

Last OP type

Last operation type

Lock (yes or no)

To check if the session holds a lock on the configuration datastore

show netconf-yang statistics

To display the statistical details for netconf-yang, use the show netconf-yang statistics command in EXEC mode.

show netconf-yang statistics

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release Modification

Release 5.3.0

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID Operation

config-services

read

Examples

This example shows how to use the show netconf-yang statistics command: 

RP/0/RP0/CPU0:router (config) #  sh netconf-yang statistics
Summary statistics                         
			                      # requests|             total time|   min time per request|   max time per request|   avg time per request|
other                             0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
close-session                     4|       0h  0m  0s   3ms|       0h  0m  0s   0ms|       0h  0m  0s   1ms|       0h  0m  0s   0ms|
kill-session                      0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
get-schema                        0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
get                               0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
get-config                        1|       0h  0m  0s   1ms|       0h  0m  0s   1ms|       0h  0m  0s   1ms|       0h  0m  0s   1ms|
edit-config                       3|       0h  0m  0s   2ms|       0h  0m  0s   0ms|       0h  0m  0s   1ms|       0h  0m  0s   0ms|
commit                            0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
cancel-commit                     0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
lock                              0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
unlock                            0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
discard-changes                   0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
validate                          0|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|       0h  0m  0s   0ms|
xml parse                         8|       0h  0m  0s   4ms|       0h  0m  0s   0ms|       0h  0m  0s   1ms|       0h  0m  0s   0ms|
netconf processor                 8|       0h  0m  0s   6ms|       0h  0m  0s   0ms|       0h  0m  0s   1ms|       0h  0m  0s   0ms|
Table 2. Field descriptions

Field name

Description

Requests

Total number of processed requests of a given type

Total time

Total processing time of all requests of a given type

Min time per request

Minimum processing time for a request of a given type

Max time per request

Maximum processing time for a request of a given type

Avg time per request

Average processing time for a request type

show ssh

To display all incoming and outgoing connections to the router, use the show ssh command in EXEC mode.

show ssh

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 5.3.2

The command output was enhanced to reflect multichannel and subsystem support for ssh.

Usage Guidelines

Use the show ssh command to display all incoming and outgoing Secure Shell (SSH) Version 1 (SSHv1) and SSH Version 2 (SSHv2) connections.

Task ID

Task ID

Operations

crypto

read

Examples

This is sample output from the show ssh command when SSH is enabled: 



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

SSH version : Cisco-2.0

id  pty   location    state         userid    host          ver       authentication
---------------------------------------------------------------------------------------------------------------
Incoming sessions

Outgoing sessions
1         0/3/CPU0    SESSION_OPEN    lab     12.22.57.     v2        password
2         0/3/CPU0    SESSION_OPEN    lab     12.22.57.75   v2        keyboard-interactive

The following output is applicable for the show ssh command starting IOS-XR 5.3.2 releases and later. 



RP/0/RP0/CPU0:router# show ssh
SSH version : Cisco-2.0  


id  chan pty     location        state           userid    host                  ver authentication connection type
--------------------------------------------------------------------------------------------------------------------------
Incoming sessions
0   1    vty0    0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  rsa-pubkey     Command-Line-Interface 
0   2    vty1    0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  rsa-pubkey     Command-Line-Interface 
0   3            0/RSP0/CPU0     SESSION_OPEN    cisco     12.22.57.75           v2  rsa-pubkey     Sftp-Subsystem         
1        vty7    0/RSP0/CPU0     SESSION_OPEN    cisco     12.22.22.57           v1  password       Command-Line-Interface 
3   1            0/RSP0/CPU0     SESSION_OPEN    lab       12.22.57.75           v2  password       Netconf-Subsystem      
4   1    vty3    0/RSP0/CPU0     SESSION_OPEN    lab       192.168.1.55          v2  password       Command-Line-Interface 

Outgoing sessions
1                0/RSP0/CPU0     SESSION_OPEN    lab       192.168.1.51          v2  password

This table describes significant fields shown in the display.

Table 3. show ssh Field Descriptions

Field

Description

id

Session identifier for the incoming and outgoing SSH connections.

chan

Channel identifier for incoming (v2) SSH connections. NULL for SSH v1 sessions.

pty

pty-id allocated for the incoming session. Null for outgoing SSH connection.

location

Specifies the location of the SSH server for an incoming connection. For an outgoing connection, location specifies from which route processor the SSH session is initiated.

state

The SSH state that the connection is currently in.

userid

Authentication, authorization and accounting (AAA) username used to connect to or from the router.

host

IP address of the remote peer.

ver

Specifies if the connection type is SSHv1 or SSHv2.

authentication

Specifies the type of authentication method chosen by the user.

connection type

Specifies which application is performed over this connection (Command-Line-Interface, Remote-Command, Scp, Sftp-Subsystem, or Netconf-Subsystem)

Related Commands

Command

Description

show sessions

Displays information about open Telnet or rlogin connections. For more information, see the System Management Command Reference for isco CRS Routers

show ssh session details

Displays the details for all the incoming and outgoing SSHv2 connections, to the router.

show ssh history

To display the last hundred SSH connections that were terminated, use the show ssh history command in EXEC mode.

show ssh history

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 6.4.1

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID

Operations

crypto

read

Examples

The following is sample output from the show ssh history command to display the last hundred SSH sessions that were teminated: 


RP/0/RP0/CPU0:router# show ssh history

SSH version : Cisco-2.0 

id       chan pty     location        userid    host                  ver authentication connection type
---------------------------------------------------------------------------------------------------------------
Incoming sessions
1        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
2        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
3        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
4        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
5        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
6        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
7        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
8        1    XXXXX   0/RP0/CPU0      root      10.105.227.252        v2  password       Netconf-Subsystem      
9        1    vty0    0/RP0/CPU0      root      10.196.98.106         v2  key-intr       Command-Line-Interface

Pty – VTY number used. This is represented as ‘XXXX’ when connection type is SFTP, SCP or Netconf.

show ssh history details

To display the last hundred SSH connections that were terminated, and also the start and end time of the session, use the show ssh history details command in EXEC mode.

show ssh history details

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 6.4.1

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID

Operations

crypto

read

Examples

The following is sample output from the show ssh history details command to display the last hundred SSH sessions that were teminated along with the start and end time of the sessions: 


RP/0/RP0/CPU0:router# show ssh history details

SSH version : Cisco-2.0 

id      key-exchange           pubkey               incipher    outcipher   inmac         outmac          start_time              end_time
------------------------------------------------------------------------------------------------------------------------------------------------------- 
Incoming Session 
1       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   14-02-18 14:00:39       14-02-18 14:00:41   
2       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   14-02-18 16:21:54       14-02-18 16:21:55   
3       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   14-02-18 16:22:18       14-02-18 16:22:19   
4       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 12:17:44       15-02-18 12:17:46   
5       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 12:18:16       15-02-18 12:18:17   
6       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 14:44:08       15-02-18 14:44:09   
7       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 14:50:15       15-02-18 14:50:16   
8       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 14:50:52       15-02-18 14:50:53   
9       ecdh-sha2-nistp256     ssh-rsa              aes128-ctr  aes128-ctr  hmac-sha2-256 hmac-sha2-256   15-02-18 15:31:26       15-02-18 15:31:38

This table describes the significant fields shown in the display.

Table 4. Field Descriptions

Field

Description

session

Session identifier for the incoming and outgoing SSH connections.

key-exchange

Key exchange algorithm chosen by both peers to authenticate each other.

pubkey

Public key algorithm chosen for key exchange.

incipher

Encryption cipher chosen for the receiver traffic.

outcipher

Encryption cipher chosen for the transmitter traffic.

inmac

Authentication (message digest) algorithm chosen for the receiver traffic.

outmac

Authentication (message digest) algorithm chosen for the transmitter traffic.

start_time

Start time of the session.

end_time

End time of the session.

show ssh session details

To display the details for all incoming and outgoing Secure Shell Version 2 (SSHv2) connections, use the show ssh session details command in EXEC mode.

show ssh session details

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

Use the show ssh session details command to display a detailed report of the SSHv2 connections to or from the router, including the cipher chosen for the specific session.

Task ID

Task ID

Operations

crypto

read

Examples

The following is sample output from the show ssh session details command to display the details for all the incoming and outgoing SSHv2 connections: 


RP/0/RP0/CPU0:router# show ssh session details

id  key-exchange               pubkey    incipher   outcipher   inmac      outmac 

---------------------------------------------------------------------------------
Incoming Session 
0  diffie-hellman-group14    ssh-rsa   aes128-ctr   aes128-ctr  hmac-sha1  hmac-sha1
1  ecdh-sha2-nistp521        ssh-rsa   aes256-ctr   aes256-ctr  hmac-sha2-512  hmac-sha2-512

This table describes the significant fields shown in the display.

Table 5. show ssh session details Field Descriptions

Field

Description

session

Session identifier for the incoming and outgoing SSH connections.

key-exchange

Key exchange algorithm chosen by both peers to authenticate each other.

pubkey

Public key algorithm chosen for key exchange.

incipher

Encryption cipher chosen for the Rx traffic.

outcipher

Encryption cipher chosen for the Tx traffic.

inmac

Authentication (message digest) algorithm chosen for the Rx traffic.

outmac

Authentication (message digest) algorithm chosen for the Tx traffic.

Related Commands

Command

Description

show sessions

Displays information about open Telnet or rlogin connections.

show ssh

Displays all the incoming and outgoing connections to the router.

ssh

To start the Secure Shell (SSH) client connection and enable an outbound connection to an SSH server, use the ssh command in EXEC mode.

ssh [vrf vrf-name] {ipv4-address | ipv6-address | hostname} [username user-id] [cipher aes {128-ctr | 192-ctr | 256-ctr}] [source-interface type interface-path-id] [command command-name]

Syntax Description

vrfvrf-name

Specifies the name of the VRF associated with this connection.

ipv4-address

IPv4 address in A:B:C:D format.

ipv6-address

IPv6 address in X:X::X format.

hostname

Hostname of the remote node. If the hostname has both IPv4 and IPv6 addresses, the IPv6 address is used.

usernameuser-id

(Optional) Specifies the username to use when logging in on the remote networking device running the SSH server. If no user ID is specified, the default is the current user ID.

cipher aes

(Optional) Specifies Advanced Encryption Standard (AES) as the cipher for the SSH client connection.

Note 
If there is no specification of a particular cipher by the administrator, the client proposes 3DES as the default to ensure compatibility.

128-CTR

128-bit keys in CTR mode.

192-CTR

192-bit keys in CTR mode.

256-CTR

256-bit keys in CTR mode.

source interface

(Optional) Specifies the source IP address of a selected interface for all outgoing SSH connections.

type

Interface type. For more information, use the question mark (? )online help function.

interface-path-id

Physical interface or virtual interface.

Note 
Use theshowinterfaces command in EXEC mode to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark(? )online help function.

command

(Optional) Specifies a remote command. Adding this keyword prompts the SSHv2 server to parse and execute thessh command in non-interactive mode instead of initiating the interactive session.

Command Default

3DES cipher

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

Support was added for the following:

  • Association of a specific VRF for the client connection was added.

  • Advanced Encryption Standard (AES) cipher with three bit lengths.

Release 3.9.1

Support for the command keyword was added.

Usage Guidelines

Use the ssh command to make an outbound client connection. The SSH client tries to make an SSHv2 connection to the remote peer. If the remote peer supports only the SSHv1 server, it internally spawns an SSHv1 connection to the remote server. The process of the remote peer version detection and spawning the appropriate client connection is transparent to the user.

If a VRF is specified in the ssh command, the ssh interface takes precedence over the interface specified in the ssh client source-interface ssh client source-interfacecommand.

When you configure the cipher aes keyword, an SSH client makes a proposal, including one or more of the key sizes you specified, as part of its request to the SSH server. The SSH server chooses the best possible cipher, based both on which ciphers that server supports and on the client proposal.


Note
AES encryption algorithm is not supported on the SSHv1 server and client. Any requests for an AES cipher sent by an SSHv2 client to an SSHv1 server are ignored, with the server using 3DES instead.

A VRF is required to run SSH, although this may be either the default VRF or a VRF specified by the user. If no VRF is specified while configuring the ssh client source-interface or ssh client knownhost commands, the default VRF is assumed.

Use the command keyword to enable the SSHv2 server to parse and execute the ssh command in non-interactive mode instead of initiating an interactive session.

Task ID

Task ID

Operations

crypto

execute

basic-services

execute

Examples

The following sample output is from the ssh command to enable an outbound SSH client connection: 


RP/0/RP0/CPU0:router# ssh  vrf green  username userabc

Password: 
Remote-host>

Related Commands

Command

Description

show ssh

Displays all the incoming and outgoing connections to the router.

ssh algorithms cipher

To configure the list of supported SSH algorithms on the client or on the server, use the ssh client algorithms cipher command or ssh server algorithms cipher command in Global Configuration mode. To remove the configuration, use the no form of this command.

ssh {client | server} algorithms cipher {aes256-cbc | aes256-ctr | aes192-ctr | aes192-cbc | aes128-ctr | aes128-cbc | aes128-gcm@openssh.com | aes256-gcm@openssh.com | 3des-cbc}

Syntax Description

client

Configures the list of supported SSH algorithms on the client.
server

Configures the list of supported SSH algorithms on the server.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release Modification
Release 7.0.1

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID Operation
crypto

read, write

Examples

This example shows how to enable CTR cipher on the client and CBC cipher on the server:


Router1#ssh client algorithms cipher aes128-ctr aes192-ctr aes256-ctr

Router1#ssh server algorithms cipher aes128-cbc aes192-cbc aes256-cbc 3des-cbc

Related Commands

Command Description

ssh client enable cipher

 Enables CBC mode ciphers on the SSH client. 

ssh server enable cipher

 Enables CBC mode ciphers on the SSH server. 

ssh client enable cipher

To enable the CBC mode ciphers 3DES-CBC and/or AES-CBC for an SSH client connection, use the ssh client enable cipher command in Global Configuration mode. To disable the ciphers, use the no form of this command.

ssh client enable cipher {aes-cbc | 3des-cbc}

Syntax Description

3des-cbc

Specifies that the 3DES-CBC cipher be enabled for the SSH client connection.

aes-cbc

Specifies that the AES-CBC cipher be enabled for the SSH client connection.

Command Default

CBC mode ciphers are disabled.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 6.3.1

This command was introduced.

Usage Guidelines

The support for CBC ciphers were disabled by default, from Cisco IOS XR Software Release 6.1.2. Hence, ssh client enable cipher and ssh server enable cipher commands were introduced to explicitly enable CBC ciphers in required scenarios.

If a client tries to reach the router which acts as a server with CBC cipher, and if the CBC cipher is not explicitly enabled on that router, then the system displays an error message: 


ssh root@x.x.x. -c aes128-cbc
Unable to negotiate with x.x.x.x port 22: no matching cipher found. 
Their offer: aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com

You must configure ssh server enable cipher aes-cbc command in this case, to connect to the router using the CBC cipher.

Task ID

Task ID Operation
crypto

read, write

Examples

The following example shows how to enable the 3DES-CBC and AES-CBC ciphers for an SSH client connection:


Router# configure
Router(config)# ssh client enable cipher aes-cbc 3des-cbc  
Router(config)# commit

Related Commands

Command Description

ssh server enable cipher

 Enables CBC mode ciphers on the SSH server. 

ssh client knownhost

To authenticate a server public key (pubkey), use the ssh client knownhost command in Global Configuration mode. To disable authentication of a server pubkey, use the no form of this command.

ssh client knownhost device: / filename

Syntax Description

device:/ filename

Complete path of the filename (for example, slot0:/server_pubkey). The colon (:) and slash (/) are required.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

The server pubkey is a cryptographic system that uses two keys at the client end—a public key known to everyone and a private, or secret, key known only to the owner of the keys. In the absence of certificates, the server pubkey is transported to the client through an out-of-band secure channel. The client stores this pubkey in its local database and compares this key against the key supplied by the server during the early stage of key negotiation for a session-building handshake. If the key is not matched or no key is found in the local database of the client, users are prompted to either accept or reject the session.

The operative assumption is that the first time the server pubkey is retrieved through an out-of-band secure channel, it is stored in the local database. This process is identical to the current model adapted by Secure Shell (SSH) implementations in the UNIX environment.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following sample output is from the ssh client knownhost command: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh client knownhost disk0:/ssh.knownhost
RP/0/RP0/CPU0:router(config)# commit
RP/0/RP0/CPU0:router# ssh host1 username user1234
Host key not found from the list of known hosts. 
Are you sure you want to continue connecting (yes/no)? yes 
Password: 
RP/0/RP0/CPU0:host1# exit
RP/0/RP0/CPU0:router# ssh host1 username user1234

ssh client source-interface

To specify the source IP address of a selected interface for all outgoing Secure Shell (SSH) connections, use the ssh client source-interface command in Global Configuration mode. To disable use of the specified interface IP address, use the no form of this command.

ssh client source-interface type interface-path-id

Syntax Description

type

Interface type. For more information, use the question mark (?) online help function.

interface-path-id

Physical interface or virtual interface.

Note 
Use the show interfaces command to see a list of all interfaces currently configured on the router.

For more information about the syntax for the router, use the question mark (? ) online help function.

Command Default

No source interface is used.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

Use the ssh client source-interface command to set the IP address of the specified interface for all outgoing SSH connections. If this command is not configured, TCP chooses the source IP address when the socket is connected, based on the outgoing interface used—which in turn is based on the route required to reach the server. This command applies to outbound shell over SSH as well as Secure Shell File Transfer Protocol (SFTP) sessions, which use the ssh client as a transport.

The source-interface configuration affects connections only to the remote host in the same address family. The system database (Sysdb) verifies that the interface specified in the command has a corresponding IP address (in the same family) configured.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows how to set the IP address of the Management Ethernet interface for all outgoing SSH connections: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh client source-interface MgmtEth 0/RP0/CPU0/0

ssh client vrf

To configure a new VRF for use by the SSH client, use the ssh client vrf command in Global Configuration mode. To remove the specified VRF, use the no form of this command.

ssh client vrf vrf-name

Syntax Description

vrf-name

Specifies the name of the VRF to be used by the SSH client.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 3.8.0

This command was introduced.

Usage Guidelines

An SSH client can have only one VRF.

If a specific VRF is not configured for the SSH client, the default VRF is assumed when applying other SSH client-related commands, such as ssh client knownhost or ssh client source-interface.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows the SSH client being configured to start with the specified VRF: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh client vrf green

Related Commands

Command

Description

ssh client dscp <value from 0 - 63>

SSH Client supports setting DSCP value in the outgoing packets. If not configured, the default DSCP value set in packets is 16 (for both client and server).

ssh server

To bring up the Secure Shell (SSH) server and to configure one or more VRFs for its use, use the ssh server command in Global Configuration mode. To stop the SSH server from receiving any further connections for the specified VRF, use the no form of this command. Optionally ACLs for IPv4 and IPv6 can be used to restrict access to the server before the port is opened.

ssh server vrf vrf-name [ ipv4 access-list ipv4 access list name ] [ ipv6 access-list ipv6 access list name ]]

ssh server v2

Syntax Description

vrf vrf-name

Specifies the name of the VRF to be used by the SSH server. The maximum VRF length is 32 characters.

Note 
If no VRF is specified, the default VRF is assumed.

ipv4 access-list access list namr

Configures an IPv4 access-list for access restrictions to the ssh server.

ipv6 access-list access list name

Configures an IPv6 access-list for access restrictions to the ssh server

v2

Forces the SSH server version to be of only version 2.

Command Default

The default SSH server version is 2 (SSHv2), which falls back to 1 (SSHv1) if the incoming SSH client connection is set to SSHv1.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

The vrf keyword was supported.

Usage Guidelines

An SSH server must be configured at minimum for one VRF. If you delete all configured VRFs, including the default, the SSH server process stops. If you do not configure a specific VRF for the SSH client when applying other commands, such as ssh client knownhost or ssh client source-interface, the default VRF is assumed.

The SSH server listens for an incoming client connection on port 22. This server handles both Secure Shell Version 1 (SSHv1) and SSHv2 incoming client connections for both IPv4 and IPv6 address families. To accept only Secure Shell Version 2 connections, use the ssh server v2 command.

To verify that the SSH server is up and running, use the show process sshd command.

Task ID

Task ID

Operations

crypto

read, write

Examples

In the following example, the SSH server is brought up to receive connections for VRF “green”: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server vrf green

Examples

In the following example, the SSH server is configured to use IPv4 ACLs: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh vrf vrf nameipv4 access-list access list name

Related Commands

Command

Description

show processes

Displays information about the SSH server.

For more information, see the System Management Command Reference for isco CRS Routers.

ssh server v2

Forces the SSH server version to be only 2 (SSHv2).

ssh server dscp <value from 0 - 63>

SSH server supports setting DSCP value in the outgoing packets. If not configured, the default DSCP value set in packets is 16 (for both client and server).

ssh server algorithms host-key

To configure the allowed SSH host-key pair algorithms from the list of auto-generated host-key pairs on the SSH server, use the ssh server algorithms host-key command in Global Configuration mode. To remove the configuration, use the no form of this command.

ssh server algorithms host-key {dsa | ecdsa-nistp256 | ecdsa-nistp384 | ecdsa-nistp521 | rsa}

Syntax Description

  • dsa

  • ecdsa-nistp256

  • ecdsa-nistp384

  • ecdsa-nistp521

  • rsa

Selects the specified DSA, ECDSA or RSA algorithm on the SSH server.

While configuring this, you can specify the algorithms in any order.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release Modification
Release 7.0.1

This command was introduced.

Usage Guidelines

This configuration is optional. If this configuration is not present, it is considered that all the SSH host-key pairs are configured. In that case, the SSH client is allowed to connect to the SSH sever with any of the host-key pairs.

You can also use the crypto key zeroize command to remove the SSH algorithms that are not required.

With the introduction of automatic generation of SSH host-key pairs, the show crypto key mypubkey command output displays the host-key pairs for all the SSH host-key pair algorithms. Prior to this, the command output displayed only the host-key pairs which were explicitly configured using the crypto key generate command.

Task ID

Task ID Operation
crypto

read, write

Examples

This example shows how to select the ecdsa algorithm from the list of auto-generated host-key pairs on the SSH server: 


Router#ssh server algorithms host-key ecdsa-nistp521

ssh disable hmac

To disable HMAC cryptographic algorithm on the SSH server, use the ssh server disable hmac command, and to disable HMAC cryptographic algorithm on the SSH client, use the ssh client disable hmac command in Global Configuration mode. To disable this feature, use the no form of this command.

ssh {client | server} disable hmac {hmac-sha1 | hmac-sha2-512}

Syntax Description

hmac-sha1

Disables the SHA-1 HMAC cryptographic algorithm.

hmac-sha2-512

Disables the SHA-2 HMAC cryptographic algorithm.

Note 
This option is available only for the server .

Command Default

None

Command Modes

Global Configuration mode

Command History

Release Modification
Release 7.0.1

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID Operation
crypto

read, write

Examples

This example shows how to disable SHA1 HMAC cryptographic algorithm on the SSH client:


Router#ssh client disable hmac hmac-sha1

This example shows how to disable SHA-2 HMAC cryptographic algorithm on the SSH server:


Router#ssh server disable hmac hmac-sha2-512

ssh server enable cipher

To enable CBC mode ciphers 3DES-CBC and/or AES-CBC for an SSH server connection, use the ssh server enable cipher command in Global Configuration mode. To disable the ciphers, use the no form of this command.

ssh server enable cipher {aes-cbc | 3des-cbc}

Syntax Description

3des-cbc

Specifies that the 3DES-CBC cipher be enabled for the SSH server connection.

aes-cbc

Specifies that the AES-CBC cipher be enabled for the SSH server connection.

Command Default

CBC mode ciphers are disabled.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 6.3.1

This command was introduced.

Usage Guidelines

The support for CBC ciphers were disabled by default, from Cisco IOS XR Software Release 6.1.2. Hence, ssh client enable cipher and ssh server enable cipher commands were introduced to explicitly enable CBC ciphers in required scenarios.

Task ID

Task ID Operation
crypto

read, write

Examples

The following example shows how to enable the 3DES-CBC and AES-CBC ciphers for an SSH server connection:


Router# configure
Router(config)# ssh server enable cipher aes-cbc 3des-cbc 
Router(config)# commit

Related Commands

Command Description

ssh client enable cipher

 Enables CBC mode ciphers on the SSH client. 

ssh server rekey-time

To configure rekey of the ssh server key based on time, use the ssh server command in Global Configuration mode. Use the no form of this command to remove the rekey interval.

ssh server rekey-time time in minutes

Syntax Description

rekey-time time in minutes

Specifies the rekey-time interval in minutes. The range is between 30 to 1440 minutes.

Note 

If no time interval is specified, the default interval is considered to be 60 minutes.

Command Default

None.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

The vrf keyword was supported.

Task ID

Task ID

Operations

crypto

read, write

Examples

In the following example, the SSH server rekey-interval of 450 minutes is used: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server rekey-time 450

ssh server rekey-volume

To configure a volume-based rekey threshold for an SSH session, use the ssh server command in Global Configuration mode. Use the no form of this command to remove the volume-based rekey threshold.

ssh server rekey-volume data in megabytes

Syntax Description

rekey-volume data in megabytes

Specifies the volume-based rekey threshold in megabytes. The range is between 1024 to 4095 megabytes.

Note 
If no volume threshold is specified, the default size is considered to be 1024 MB.

Command Default

None.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

The vrf keyword was supported.

Task ID

Task ID

Operations

crypto

read, write

Examples

In the following example, the SSH server rekey-volume of 2048 minutes is used: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh  rekey-volume 2048

show ssh rekey

To display session rekey details such as session id, session rekey count, time to rekey, data to rekey, use the show ssh rekey command in EXEC mode.

show ssh rekey

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

The ssh rekey data is updated ten times between two consecutive rekeys.

Task ID

Task ID

Operations

crypto

read

Examples

The following sample output is from the show ssh rekey command: 


	# show ssh rekey

id    RekeyCount   TimeToRekey(min)     VolumeToRekey(MB) 
----------------------------------------------------------
Incoming Session 
0        8                59.5             1024.0

This table describes the fields shown in the display.

Table 6. show ssh rekey Field Descriptions

Field

Description

Rekey Count

Number of times the ssh rekey is generated.

TimeToRekey

Time remaining (in minutes) before the ssh rekey is regenerated based on the value set using the ssh server rekey-time command.

VolumeToRekey

Volume remaining (in megabytes) before the ssh rekey is regenerated based on the value set using the ssh server rekey-volume command.

ssh server logging

To enable SSH server logging, use the ssh server logging command in Global Configuration mode. To discontinue SSH server logging, use the no form of this command.

ssh server logging

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 3.8.0

This command was introduced.

Usage Guidelines

Once you configure the logging, the following messages are displayed:

  • Warning: The requested term-type is not supported

  • SSH v2 connection from %s succeeded (user:%s, cipher:%s, mac:%s, pty:%s)

The warning message appears if you try to connect using an unsupported terminal type. Routers running the Cisco IOS XR software support only the vt100 terminal type.

The second message confirms a successful login.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows the initiation of an SSH server logging: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server logging

Related Commands

Command

Description

ssh server

Initiates the SSH server.

ssh server rate-limit

To limit the number of incoming Secure Shell (SSH) connection requests allowed per minute, use the ssh server rate-limit command in Global Configuration mode. To return to the default value, use the no form of this command.

ssh server rate-limit rate-limit

Syntax Description

rate-limit

Number of incoming SSH connection requests allowed per minute. Range is from 1 to 120.When setting it to 60 attempts per minute, it basically means that we can only allow 1 per second. If you set up 2 sessions at the same time from 2 different consoles, one of them will get rate limited. This is connection attempts to the ssh server, not bound per interface/username or anything like that. So value of 30 means 1 session per 2 seconds and so forth.

Command Default

rate-limit: 60 connection requests per minute

Command Modes

Global Configuration mode

Usage Guidelines

Use the ssh server rate-limit command to limit the incoming SSH connection requests to the configured rate. Any connection request beyond the rate limit is rejected by the SSH server. Changing the rate limit does not affect established SSH sessions.

If, for example, the rate-limit argument is set to 30, then 30 requests are allowed per minute, or more precisely, a two-second interval between connections is enforced.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows how to set the limit of incoming SSH connection requests to 20 per minute: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server rate-limit 20

ssh server session-limit

To configure the number of allowable concurrent incoming Secure Shell (SSH) sessions, use the ssh server session-limit command in Global Configuration mode. To return to the default value, use the no form of this command.

ssh server session-limit sessions

Syntax Description

sessions

Number of incoming SSH sessions allowed across the router. The range is from 1 to 100.

Note 
Although CLI output option has 1024, you are recommended to configure session-limit not more than 100. High session count may cause resource exhaustion .

Command Default

sessions: 64 per router

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

Use the ssh server session-limit command to configure the limit of allowable concurrent incoming SSH connections. Outgoing connections are not part of the limit.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows how to set the limit of incoming SSH connections to 50: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server session-limit 50

Related Commands

Command

Description

show processes

Displays information about the SSH server.

For more information, see System Management Command Reference for isco CRS Routers.

ssh server v2

To force the SSH server version to be only 2 (SSHv2), use the ssh server v2 command in Global Configuration mode. To bring down an SSH server for SSHv2, use the no form of this command.

ssh server v2

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 3.3.0

This command was introduced.

Usage Guidelines

Only SSHv2 client connections are allowed.

Task ID

Task ID

Operations

crypto

read, write

Examples

The following example shows how to initiate the SSH server version to be only SSHv2: 


 RP/0/RP0/CPU0:router#configure
RP/0/RP0/CPU0:router(config)# ssh server v2

Related Commands

Command

Description

ssh server

Initiates the SSH server.

ssh server netconf port

To configure a port for the netconf SSH server, use the ssh server netconf port command in Global Configuration mode. To return to the default port, use the no form of the command.

ssh server netconf port port number

Syntax Description

port port-number

Port number for the netconf SSH server (default port number is 830).

Command Default

The default port number is 830.

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Release 3.8.0

The vrf keyword was supported.

Release 6.0

The ssh server netconf command is no longer auto completed to configure the default port. This command is now optional

Usage Guidelines

Starting with IOS-XR 6.0.0 it is no longer sufficient to configure a netconf port to enable netconf subsystem support. ssh server netconf needs to be at least configured for one vrf.

Task ID

Task ID

Operations

crypto

read, write

Examples

This example shows how to use the ssh server netconf port command with port 831: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh server netconf port 831

Related Commands

Command

Description

ssh server netconf

Configures the vrf(s), where netconf subsystem requests are to be received.

netconf-yang agent ssh

Configures the ssh netconf-yang backend for the netconf subsystem (Required to allow the system to service netconf-yang requests).

For more information, see the Cisco ASR 9000 Series Aggregation Services Router System Management Command Reference.

ssh server netconf

To bring up the netconf subsystem support using a dedicated communication port with the Secure Shell (SSH) server and to configure one or more VRFs for its use, use the ssh server netconf command in Global Configuration mode. To stop the SSH server from receiving any further netconf subsystem connections for the specified VRF, use the no form of this command.

Optionally ACLs for IPv4 and IPv6 can be used to restrict access to the netconf subsystem of the SSH server before the port is opened.

ssh server netconf [ vrfvrf name[ ipv4 access-list access list name ] [ ipv6 access-list access list name] ]

Syntax Description

vrf name

Specifies the name of the VRF to be used by the netconf subsystem of the SSH server. The maximum VRF length is 32 characters.

Note 
If no VRF is specified, the default VRF is assumed.
IPv4 access list name

Configures an IPv4 access-list for access restrictions to the netconf subsystem of the SSH server.

IPv6 access list name

Configures an IPv6 access-list for access restrictions to the netconf subsystem of the SSH server.

Command Default

If no vrf is specified, the command is auto expanded using the default vrf.

Command Modes

Global Configuration mode

Command History

Release Modification

Release 5.3.0

This command was introduced.

Release 6.0.0

The ssh server netconf command is no longer auto completed to configure the default port. The vrf keyword was supported.

Without parameter the command is now auto expanded to enable the netconf subsystem for vrf default. To start netconf subsystem support at least one vrf needs to be configured.

Usage Guidelines

Netconf subsystem support of the SSH server must be configured at minimum for one VRF. If you delete all configured VRFs, including the default, the SSH server process stops serving the netconf subsystem requests. If you do not configure a specific VRF the default VRF is assumed. The SSH server listens for netconf subsystem connections an incoming client connection on the configured port (using ssh server netconf port) or port 8030 (as the iana assigned default port)

Netconf subsystem support is only available with Secure Shell Version 2 SSHv2 incoming client connections for both IPv4 and IPv6 address families. To verify that the SSH server is up and running, use the show process sshd command.

Task ID

Task ID Operation

crypto

read, write

Examples

This example shows how to use the ssh server netconf vrfvrf name command: 

RP/0/RP0/CPU0:router (config) #  ssh server netconf vrf red

show tech-support ssh

To automatically run show commands that display system information, use the show tech-support command, use the show tech-support ssh command in EXEC mode.

show tech-support ssh

Syntax Description

This command has no keywords or arguments.

Command Default

None

Command Modes

EXEC mode

Command History

Release

Modification

Release 6.4.1

This command was introduced.

Usage Guidelines

No specific guidelines impact the use of this command.

Task ID

Task ID

Operations

crypto

read

Examples

The following is sample output from the show tech-support ssh command: 


RP/0/RP0/CPU0:router# show tech-support ssh
++ Show tech start time: 2018-Feb-20.123016.IST ++
Tue Feb 20 12:30:27 IST 2018 Waiting for gathering to complete
.............................
Tue Feb 20 12:32:35 IST 2018 Compressing show tech output
Show tech output available at 0/RP0/CPU0 : /harddisk:/showtech/showtech-ssh-2018-Feb-20.123016.IST.tgz
++ Show tech end time: 2018-Feb-20.123236.IST ++
RP/0/RP0/CPU0:turin-sec1#

The show tech-support ssh command collects the output of these CLI:

Command

Description

show logging

Displays the contents of the logging buffer.

show context location all
show running-config

Displays the contents of the currently running configuration or a subset of that configuration.
show ip int brief

Displays brief information about each interface.

show ssh

Displays all incoming and outgoing connections to the router.
show ssh session details

Displays the details for all the incoming and outgoing SSHv2 connections, to the router.

show ssh rekey

Displays session rekey details such as session id, session rekey count, time to rekey, data to rekey.

show ssh history

Displays the last hundred SSH connections that were terminated.
show tty trace info all all
show tty trace error all all

ssh timeout

To configure the timeout value for authentication, authorization, and accounting (AAA) user authentication, use the ssh timeout command in Global Configuration mode. To set the timeout value to the default time, use the no form of this command.

ssh timeout seconds

Syntax Description

seconds

Time period (in seconds) for user authentication. The range is from 5 to 120.

Command Default

seconds: 30

Command Modes

Global Configuration mode

Command History

Release

Modification

Release 2.0

This command was introduced.

Usage Guidelines

Use the ssh timeout command to configure the timeout value for user authentication to AAA. If the user fails to authenticate itself within the configured time to AAA, the connection is terminated. If no value is configured, the default value of 30 seconds is used.

Task ID

Task ID

Operations

crypto

read, write

Examples

In the following example, the timeout value for AAA user authentication is set to 60 seconds: 


RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# ssh timeout 60