The Function of the Community String Field in a Trap PDU

B.

In Simple Network Management Protocol (SNMP), a trap PDU (Protocol Data Unit) is a message sent from an SNMP agent to a management station to notify it of an event or condition that has occurred. The Community String field is a critical component of the trap PDU and plays an essential role in SNMP security.

The Community String is a password-like string of characters that acts as an authentication mechanism between the SNMP agent and the management station. It is used to ensure that only authorized management stations can receive SNMP messages from the agent.

Option B is the correct answer. The Community String allows authentication by management stations. When a management station sends an SNMP request to an agent, it includes a Community String in the request message. The agent verifies the Community String against its own stored value for that particular community name. If the strings match, the agent accepts the request and responds to it. If the strings do not match, the agent rejects the request and does not respond.

The Community String also plays a role in controlling access to SNMP information. SNMP agents can be configured to respond differently to SNMP requests based on the Community String provided in the request message. For example, a read-only Community String might be allowed to retrieve SNMP information, while a read-write Community String might be allowed to retrieve and modify SNMP information.

In summary, the Community String field in a trap PDU is used for authentication and access control purposes in SNMP, and its function is to allow authentication by management stations.