352-001 · Question #47
What is the function of the Community String field defined in a trap PDU?
The correct answer is B. allow authentication by management station. The Community String in an SNMP trap PDU is a plaintext shared secret that allows the receiving management station to authenticate the source of the trap before processing it.
Question
What is the function of the Community String field defined in a trap PDU?
Options
- Aenable the routing of messages
- Ballow authentication by management station
- Cenable reliable delivery of messages
- Disolate the PDU within a defined region of the network
How the community answered
(23 responses)- B87% (20)
- C4% (1)
- D9% (2)
Why each option
The Community String in an SNMP trap PDU is a plaintext shared secret that allows the receiving management station to authenticate the source of the trap before processing it.
Community strings are not used by the network infrastructure to route SNMP messages - routing decisions are made by the underlying IP layer, independent of SNMP community strings.
In SNMPv1 and SNMPv2c, the community string functions as a simple password embedded in every PDU, including traps. When a trap arrives, the management station compares the included community string against its configured list of valid strings to decide whether to accept or discard the message, providing rudimentary source authentication for trap PDUs.
SNMP traps are transmitted over UDP and provide no delivery guarantee - the community string is purely an authentication field and adds no reliability or acknowledgment mechanism.
Community strings do not segment or confine PDUs to a network region - network segmentation is achieved through VLANs, ACLs, or SNMP views, not community strings.
Concept tested: SNMP community string authentication in trap PDUs
Source: https://www.rfc-editor.org/rfc/rfc1157
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