Configure Secure Shell (SSH) server parameters
Full book title
461
Command Session IP Address a.b.c.d Port p
The values in these two text boxes are used to specify the host IP address and port number
that the router will use to handle incoming requests for a command session from SSH clients.
This is instead of the router’s normal command interpreter. For example, if the values are IP
address
127.0.0.1
, port
4000
, the SSH client will make a direct connection to
ASY 0
and the
device attached to
ASY 0
will receive and process the commands from the SSH client.
Enable support for SSH v1.5
When enabled, the server negotiates SSH V1.5. The router must also have a SSH V1 key
present and the filename entered into the SSG configuration.
Server key size
This option applies to V1 SSH. During initialization of an SSH session, the server sends its host
key and a server key (which should be of a different size to the host key). The router generates
this key automatically but the length of the server key is determined by this parameter. If
when this value is set it is too similar to the length of the host key, the router will automatically
adjust the selected value so that the key sizes are significantly different.
Enable support for SSH v2.0
When enabled, the server negotiates SSH V2. The router must also have a SSH V2 key present
and the filename entered into the SSG configuration.
Actively start key exchange
This option applies to V2 SSH. Some SSH clients wait for the server to initiate the key exchange
process when a new SSH session is started unless they have data to send to the server, in
which case they will initiate the key exchange themselves. When checked, this checkbox
causes the router to automatically initiate a key exchange without waiting for the client.
Rekey Never/After n units of data have been transferred
With SSH V2, it is possible to negotiate new encryption keys after the current ones have been
used to encrypt a specified amount of data. The radio buttons select whether this feature
should be used. If this feature is to be used the amount of data is entered into the text box
and the applicable units (
Kbytes
,
Mbytes
,
Gbytes
) selected from the drop-down list.
Encryption Preferences
The following four configuration options allocate preferences to the encryption method that
should be used to encrypt data on the link. A lower value indicates greater preference apart
from zero which disables the option.
3DES
The preference level for the Triple-DES algorithm.
AES (128 bits)
The preference level for the 128-bit AES algorithm.
AES (192 bits)
The preference level for the AES algorithm using 192 bits.
AES (256 bits)
The the preference level for the AES algorithm using 256 bits.
