A group of hosts managed by Simple Network Management Protocol (SNMP) running SNMP agents. Communities provide a simple way of partitioning and securing a network for SNMP management. SNMP agents and management systems use community names as the mechanism for authenticating SNMP messages.
All SNMP agents belonging to the same community share the same community name, which functions as a kind of shared password for those agents so that they can be recognized by the SNMP management program and other agents. SNMP messages sent by SNMP management systems to a specific community are accepted only by hosts configured to belong to that community.
If an SNMP agent program receives an SNMP message with a community name that it is not configured to recognize, it typically drops the message and sends a trap message to the SNMP management program indicating that a message was not authenticated on that machine.
An agent can be a member of one or more communities. By default, all agents belong to the public community. If all community names including public names are removed from an SNMP-managed host, the host will accept all SNMP messages sent to it.