Refer to the exhibit. A customer reports that Host-1 is failing to receive streaming traffic from the IPTV source. The engineer has confirmed that hosts on router R2 are receiving traffic normally…

Question

Exhibit

Options

• AConfigure IP PIM SSM and IGMP version 2 under interface GigatxtEthernet 1/0/1 on R3
• BConfigure IGMP version 3 under interface GigabitEthernet 1/0/1 on R3
• CRemove IP PIM SSM and IGMP from interface GigaEthernet 1/0/1 on R3 and configure under global
• DRemove IP PIM SSM from the global configuration on R3 and configure it under the GigabitEthernet

• A
  2% (1)
• B
  83% (35)
• C
  5% (2)
• D
  10% (4)

Explanation

Option B is correct because PIM SSM (Source Specific Multicast) requires IGMPv3 on any host-facing interface. IGMPv3 enables hosts to send (S,G) join reports that specify both the multicast group and the source address - exactly what SSM needs to build its forwarding state. Without IGMPv3 on R3's Gi1/0/1 (the interface toward Host-1), the router cannot process Host-1's source-specific membership requests, so traffic never flows downstream even though the subscription messages are being sent.

Why the distractors fail:

• A is wrong because adding IGMPv2 alongside PIM SSM doesn't help - IGMPv2 only supports (*,G) any-source joins, which are fundamentally incompatible with SSM; you'd still have the same problem.
• C is wrong because IGMP configuration must live on the interface (where hosts attach), not globally; moving it to global config is not valid IOS syntax and wouldn't fix the issue.
• D is wrong because PIM SSM is correctly configured globally (that's the standard placement via ip pim ssm default or a defined range); removing it from global breaks multicast for the entire router.

Memory tip: Think "SSM = Source needs Specific Sender → needs IGMPv3." Whenever you see PIM SSM on a router, any interface with directly connected receivers must run IGMPv3 - no exceptions.

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