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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 Cisco IOS XR Software module in the Cisco IOS XR System Security Configuration Guide for the Cisco XR 12000 Series Router.
- clear ssh
- sftp
- sftp (Interactive Mode)
- show ssh
- show ssh session details
- ssh
- ssh client knownhost
- ssh client source-interface
- ssh client vrf
- ssh server
- ssh server logging
- ssh server rate-limit
- ssh server session-limit
- ssh server v2
- ssh timeout
clear ssh
To terminate an incoming or outgoing Secure Shell (SSH) connection, use the clear ssh command in EXEC mode.
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 History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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/0/0/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/0/0/CPU0:router# clear ssh 0sftp
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-filename
(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 History
Release
Modification
Release 3.2
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
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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/0/0/CPU0:router# sftp abc@ena-view1:ssh.diff disk0In 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/0/0/CPU0:router# sftp disk0:/sam_* abc@ena-view1:/users/abc/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-filename
(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 History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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 abc is downloading the file ssh.diff from the SFTP server ena-view1 to disk0:
RP/0/0/CPU0:router# sftp abc@ena-view1:ssh.diff disk0In 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/0/0/CPU0:router# sftp disk0:/sam_* abc@ena-view1:/users/abc/show ssh
To display all incoming and outgoing connections to the router, use the show ssh command in EXEC mode.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
Examples
The following sample output is from the show ssh command when SSH is enabled:
RP/0/0/CPU0:router# show ssh SSH version: Cisco-2.0 id pty location state userid host ver ------------------------------------------------------------------------ Incoming sessions 0 vty0 0/0/CPU0 SESSION_OPEN cisco 172.19.72.182 v2 1 vty1 0/0/CPU0 SESSION_OPEN cisco 172.18.0.5 v2 2 vty2 0/0/CPU0 SESSION_OPEN cisco 172.20.10.3 v1 3 vty3 0/0/CPU0 SESSION_OPEN cisco 3333::50 v2 Outgoing sessions 1 0/0/CPU0 SUSPENDED root 172.19.72.182 v2Table 1 describes the significant fields shown in the display.
Table 1 show ssh Field Descriptions Field
Description
session
Session identifier for the incoming and outgoing SSH connections.
pty
pty-id allocated for the incoming session. Null for outgoing SSH connection.
location
Specifies where the SSH server is running for 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.
Related Commands
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.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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/0/0/CPU0:router# show ssh session details SSH version: Cisco-2.0 session key-exchange pubkey incipher outcipher inmac outmac ------------------------------------------------------------------------------- Incoming Session 0 diffie-hellman ssh-dss 3des-cbc 3des-cbc hmac-md5 hmac-md5 Outgoing connection 1 diffie-hellman ssh-dss 3des-cbc 3des-cbc hmac-md5 hmac-md5Table 1 describes the significant fields shown in the display.
Table 2 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.
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-cbc | 192-cbc | 256-cbc } ] [ source-interface type interface-path-id ] [ command command-name ]
Syntax Description
vrf vrf-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.
username user-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-CBC
128-bit keys in CBC mode.
192-CBC
192-bit keys in CBC mode.
256-CBC
256-bit keys in CBC 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 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.
command
(Optional) Specifies a remote command. Adding this keyword prompts the SSHv2 server to parse and execute the ssh command in non-interactive mode instead of initiating the interactive session.
command name
Name of the remote command keyword.
Command History
Release
Modification
Release 3.2
This command was introduced.
Release 3.8.0
Support was added for the following:
Release 3.9.1
Support for the command keyword was added.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
Examples
The following sample output is from the ssh command to enable an outbound SSH client connection:
RP/0/0/CPU0:router# sshvrf green username userabc Password: Remote-host>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.
Syntax Description
device:/ filename
Complete path of the filename (for example, slot0:/server_pubkey). The colon (:) and slash (/) are required.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
Examples
The following sample output is from the ssh client knownhost command:
RP/0/0/CPU0:router# configure RP/0/0/CPU0:router(config)# ssh client knownhost disk0:/ssh.knownhost RP/0/0/CPU0:router(config)# commit RP/0/0/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/0/0/CPU0:host1# exit RP/0/0/CPU0:router# ssh host1 username user1234ssh 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
no 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 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 History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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.
Syntax Description
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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.
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.
v2
Forces the SSH server version to be only 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 History
Release
Modification
Release 3.2
This command was introduced.
Release 3.8.0
The vrf keyword was supported.
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
Examples
In the following example, the SSH server is brought up to receive connections for VRF “green:”
RP/0/0/CPU0:router# configure RP/0/0/CPU0:router(config)# ssh server vrf greenssh 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.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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
no ssh server rate-limit
Syntax Description
rate-limit
Number of incoming SSH connection requests allowed per minute. Range is from 1 to 120.
Command History
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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.
Syntax Description
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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
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.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
Only SSHv2 client connections are allowed.
Task ID
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
no ssh timeout seconds
Syntax Description
seconds
Time period (in seconds) for user authentication. The range is from 5 to 120.
Command History
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes the proper task IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.
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 aborted. If no value is configured, the default value of 30 seconds is used.
Task ID
Task ID
Operations
crypto
read, write
