Admin Guide

Table Of Contents
passphrase encrypts and further protects the key files, you must provide a passphrase to decrypt
the key files as part of the DSA authentication. The following is an example of DSA public key
authentication between the VSP SSHv2 client and the SSHv2 server:
Linux/PC ssh (DSA authorization) > VSP ssh (DSA authorization) > VSP ssh (DSA
authorization) > VSP
To attempt public key authentication, the SSHv2 client looks for the associated DSA key pair files in
the /intflash/.ssh directory. If no DSA key pair files are found, the SSHv2 client automatically
prompts you for password authentication. If the SSHv2 client succeeds with the authentication, then
a new secured SSHv2 session is established to the remote SSHv2 server. For more information,
see
Table 38: DSA authentication access level and file name on page 149.
Important:
If you configure the DSA user key with a passphrase but you do not supply the correct passphrase
when you try to make the SSHv2 connection, then the system defaults back to the password
authentication. If the SSHv2 client succeeds with the authentication, then a new secured SSHv2
session is established to the remote SSHv2 server.
SSH version 2
SSH version 2 (SSHv2) protocol is a complete rewrite of the SSHv1 protocol. In SSHv2 the
functions are divided among three layers:
SSH Transport Layer (SSH-TRANS)
The SSH Transport Layer manages the server authentication and provides the initial
connection between the client and the server. Once the connection is established, the
Transport Layer provides a secure, full-duplex connection between the client and server.
SSH Authentication Protocol (SSH-AUTH)
The SSH Authentication Protocol runs on top of the SSH Transport Layer and authenticates
the client-side user to the server. SSH-AUTH defines three authentication methods: public key,
host-based, and password. SSH-AUTH provides a single authenticated tunnel for the SSH
connection protocol.
SSH Connection Protocol (SSH-CONN)
The SSH Connection Protocol runs on top of the SSH Transport Layer and user authentication
protocols. SSH-CONN provides interactive logon sessions, remote execution of commands,
forwarded TCP/IP connections, and forwarded X11 connections. These services are
multiplexed into the single encrypted tunnel provided by the SSH transport layer.
The following figure shows the three layers of the SSHv2 protocol.
Secure Shell fundamentals
October 2015 Administering Avaya VSP 7200 Series and 8000 Series 143
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