ssh2

Use ssh2 to establish a connection to an IPv4 Stelnet server.

Syntax

In non-FIPS mode:

ssh2 server [ port-number ] [ vpn-instance vpn-instance-name ] [ identity-key { dsa | ecdsa-sha2-nistp256 | ecdsa-sha2-nistp384 | rsa | { x509v3-ecdsa-sha2-nistp256 | x509v3-ecdsa-sha2-nistp384 } pki-domain domain-name| prefer-compress zlib | prefer-ctos-cipher { 3des-cbc |aes128-cbc | aes128-ctr | aes128-gcm | aes192-ctr | aes256-cbc | aes256-ctr | aes256-gcm | des-cbc } | prefer-ctos-hmac { md5 | md5-96 | sha1 | sha1-96 | sha2-256 | sha2-512 } | prefer-kex { dh-group-exchange-sha1 | dh-group1-sha1 | dh-group14-sha1 | ecdh-sha2-nistp256 | ecdh-sha2-nistp384 } | prefer-stoc-cipher { 3des-cbc |aes128-cbc | aes128-ctr | aes128-gcm | aes192-ctr | aes256-cbc | aes256-ctr | aes256-gcm | des-cbc } | prefer-stoc-hmac { md5 | md5-96 | sha1 | sha1-96 | sha2-256 | sha2-512 } ] * [ dscp dscp-value | escape character |{ public-key keyname | server-pki-domain domain-name } | source { interface interface-type interface-number | ip ip-address } ] *

In FIPS mode:

ssh2 server [ port-number ] [ vpn-instance vpn-instance-name ] [ identity-key { ecdsa-sha2-nistp256 | ecdsa-sha2-nistp384 | rsa | { x509v3-ecdsa-sha2-nistp256 | x509v3-ecdsa-sha2-nistp384 } pki-domain domain-name} | prefer-compress zlib | prefer-ctos-cipher { aes128-cbc | aes128-ctr | aes128-gcm | aes192-ctr | aes256-cbc | aes256-ctr | aes256-gcm } | prefer-ctos-hmac { sha1 | sha1-96 | sha2-256 | sha2-512 } | prefer-kex { dh-group14-sha1 | ecdh-sha2-nistp256 | ecdh-sha2-nistp384 } | prefer-stoc-cipher { aes128-cbc | aes128-ctr | aes128-gcm | aes192-ctr | aes256-cbc | aes256-ctr | aes256-gcm } | prefer-stoc-hmac { sha1 | sha1-96 | sha2-256 | sha2-512 } ] * [ escape character | { public-key keyname | server-pki-domain domain-name }| source { interface interface-type interface-number | ip ip-address } ] *

Views

User view

Predefined user roles

network-admin

mdc-admin

Parameters

server: Specifies a server by its IPv4 address or host name, a case-insensitive string of 1 to 253 characters.

port-number: Specifies the port number of the server, in the range 1 to 65535. The default is 22.

vpn-instance vpn-instance-name: Specifies the MPLS L3VPN instance to which the server belongs. The vpn-instance-name argument represents the VPN instance name, a case-sensitive string of 1 to 31 characters.

identity-key: Specifies a public key algorithm for publickey authentication of the client. The default is DSA in non-FIPS mode and is RSA in FIPS mode. If the server uses publickey authentication, you must specify this keyword. The client generates the digital signature or certificate by using the local private key that is associated with the specified algorithm.

prefer-compress: Specifies the preferred compression algorithm for data compression between the server and the client. By default, compression is not supported.

zlib: Specifies compression algorithm zlib.

prefer-ctos-cipher: Specifies the preferred client-to-server encryption algorithm. The default is AES128-CTR. Supported algorithms are DES-CBC, 3DES-CBC, AES128-CBC, AES128-CTR, AES128-GCM, AES192-CTR, AES256-CBC, AES256-CTR, and AES256-GCM, in ascending order of security strength and computation time.

prefer-ctos-hmac: Specifies the preferred client-to-server HMAC algorithm. The default is SHA2-256. Supported algorithms are MD5, MD5-96, SHA1, SHA1-96, SHA2-256, SHA2-512, in ascending order of security strength and computation time.

prefer-kex: Specifies the preferred key exchange algorithm. The default is ecdh-sha2-nistp256. Supported algorithms are diffie-hellman-group-exchange-sha1, diffie-hellman-group1-sha1, diffie-hellman-group14-sha1, ecdh-sha2-nistp256, and ecdh-sha2-nistp384, in ascending order of security strength and computation time.

prefer-stoc-cipher: Specifies the preferred server-to-client encryption algorithm. The default is AES128-CTR. Supported algorithms are the same as the client-to-server encryption algorithms (see the prefer-ctos-cipher keyword).

prefer-stoc-hmac: Specifies the preferred server-to-client HMAC algorithm. The default is SHA2-256. Supported algorithms are the same as the client-to-server HMAC algorithms (see the prefer-ctos-hmac keyword).

dscp dscp-value: Specifies the DSCP value in the IPv4 SSH packets. The value range for the dscp-value argument is 0 to 63, and the default value is 48. The DSCP value determines the transmission priority of the packet.

escape character: Specifies a case-sensitive escape character. By default, the escape character is a tilde (~).

public-key keyname: Specifies the host public key of the server that the client uses to authenticate the server. The keyname argument is a case-insensitive string of 1 to 64 characters.

server-pki-domain domain-name: Specifies the PKI domain for verifying the server's certificate. The domain-name argument represents the PKI domain name, a case-insensitive string of 1 to 31 characters. Invalid characters are tildes (~), asterisks (*), backslashes (\), vertical bars (|), colons (:), dots (.), angle brackets (< >), quotation marks ("), and apostrophes (').

source: Specifies a source IPv4 address or source interface for SSH packets. By default, the device uses the primary IPv4 address of the output interface in the routing entry as the source address of SSH packets. As a best practice to ensure successful Stelnet connections, specify a loopback interface as the source interface or specify that interface's IPv4 address as the source IPv4 address.

Usage guidelines

The combination of an escape character and a dot (.) works as an escape sequence. This escape sequence is typically used to quickly terminate an SSH connection when the server reboots or malfunctions.

For the escape sequence to take effect, you must enter it at the very beginning of a line. If you have entered other characters or performed operations in a line, enter the escape sequence in the next line.

As a best practice, use the default escape character (~). Do not use any character in SSH usernames as the escape character.

If the client and the server have negotiated to use certificate authentication, the client must verify the server's certificate. For the client to correctly get the server's certificate, you must specify the server's PKI domain on the client by using the server-pki-domain domain-name option. The client uses the CA certificate stored in the specified PKI domain to verify the server's certificate and does not need to save the server's public key before authentication. If you do not specify the server's PKI domain, the client uses the PKI domain of its own certificate to verify the server's certificate.

Examples

# Establish a connection to Stelnet server 3.3.3.3 and specify the public key of the server as svkey. The Stelnet client uses publickey authentication. Specify the dollar sign ($) as the escape character. Use the following algorithms:

<Sysname> ssh2 3.3.3.3 prefer-kex dh-group14-sha1 prefer-stoc-cipher aes128-cbc prefer-ctos-hmac sha1 prefer-stoc-hmac sha1-96 prefer-compress zlib public-key svkey escape $