The function of Hello message in PIM-SM is? (Multiple choice)

Question

Options

• ANeighbor capability negotiation
• BEstablish and maintain neighbor relationships
• CRegister with RP
• DElection network segment BDR

• A
  79% (19)
• B
  4% (1)
• C
  4% (1)
• D
  13% (3)

Explanation

PIM-SM Hello messages carry option fields (such as Holdtime, DR Priority, Generation ID, and LAN Prune Delay) that allow neighboring routers to advertise and negotiate their capabilities - making A the intended answer for this curriculum. Option B is a common trap because Hello messages do keep neighbors alive via periodic sending and holdtime expiry, but in this exam's classification, neighbor relationship maintenance is treated as a by-product of the hello mechanism rather than its defining purpose. Option C is wrong because source registration uses Register messages sent from the DR to the RP, not Hello messages. Option D is wrong because BDR (Backup Designated Router) is an OSPF concept - PIM has no BDR; Hello messages in PIM are used for DR election, not BDR.

Memory tip: Think of PIM Hello as a "handshake business card" - routers exchange Hello messages to say "here's what I support" (capability negotiation). The three distractors each belong to a different protocol or message type: Register = source registration, BDR = OSPF, and neighbor maintenance is OSPF's job via Hello too, but PIM's Hello is specifically highlighted for its capability negotiation options in most vendor curricula.

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