The SNMP community string is a shared “secret” among the
SNMP management station and the SNMP network agents being managed. This is
called a community key because it can be used to define a
data-exchanging group of agent and management stations within a larger network.
The default key for the PIX Firewall, like many network devices, is public. This is also a routine default entry in most sniffer,
mapping, or other reconnaissance tools, so common sense says to change it.
The PIX Firewall uses the community key to determine if the
incoming SNMP request is valid. Use the configuration mode
snmp-server community command to enter the key value used by the SNMP
management station(s). The key is case sensitive and can be up to 32 characters
long. No spaces are allowed. Typing a new snmp-server
community command replaces the default public entry or any other existing
community key. Use the no form of the command to turn off the feature. The
Pix(config)# snmp-server community key
Pix(config)# no snmp-server community key