Administrator Guide

Removing the RSA Host Keys and Zeroizing Storage
Use the crypto key zeroize rsa command to delete the host key pairs, both the public and private key information for RSA 1 and
or RSA 2 types. Note that when FIPS mode is enabled there is no RSA 1 key pair. Any memory currently holding these keys is zeroized
(written over with zeroes) and the NVRAM location where the keys are stored for persistence across reboots is also zeroized.
To remove the generated RSA host keys and zeroize the key storage location, use the crypto key zeroize rsa command in
CONFIGURATION mode.
DellEMC(conf)#crypto key zeroize rsa
Configuring When to Re-generate an SSH Key
You can configure the time-based or volume-based rekey threshold for an SSH session. If both threshold types are configured, the session
rekeys when either one of the thresholds is reached.
To configure the time or volume rekey threshold at which to re-generate the SSH key during an SSH session, use the ip ssh rekey
[time rekey-interval] [volume rekey-limit] command. CONFIGURATION mode.
Configure the following parameters:
• rekey-interval: time-based rekey threshold for an SSH session. The range is from 10 to 1440 minutes. The default is 60 minutes.
• rekey-limit: volume-based rekey threshold for an SSH session. The range is from 1 to 4096 to megabytes. The default is 1024
megabytes.
Examples
The following example configures the time-based rekey threshold for an SSH session to 30 minutes.
DellEMC(conf)#ip ssh rekey time 30
The following example configures the volume-based rekey threshold for an SSH session to 4096 megabytes.
DellEMC(conf)#ip ssh rekey volume 4096
Configuring the SSH Server Key Exchange Algorithm
To configure the key exchange algorithm for the SSH server, use the ip ssh server kex key-exchange-algorithm command
in CONFIGURATION mode.
key-exchange-algorithm : Enter a space-delimited list of key exchange algorithms that will be used by the SSH server.
The following key exchange algorithms are available:
• diffie-hellman-group-exchange-sha1
• diffie-hellman-group1-sha1
• diffie-hellman-group14-sha1
The default key exchange algorithms are the following:
• diffie-hellman-group-exchange-sha1
• diffie-hellman-group1-sha1
• diffie-hellman-group14-sha1
When FIPS is enabled, the default is diffie-hellman-group14-sha1.
Example of Configuring a Key Exchange Algorithm
The following example shows you how to configure a key exchange algorithm.
DellEMC(conf)# ip ssh server kex diffie-hellman-group-exchange-sha1 diffie-hellman-group14-
sha1
686
Security