CCNP Practice Question: Examine the following configuration on a Cisco…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  The interface will operate in dense-mode for all multicast groups because no RP is configured.

  Why it's wrong here

  The presence of "ip pim sparse-dense-mode" on the interface does not force dense-mode for all multicast groups; instead, it lets PIM choose per-group based on whether an RP is known. If no RP exists for the group, the router falls back to dense-mode flooding, but if an RP is discovered dynamically or configured statically, it uses sparse-mode operation. Therefore, saying the interface operates in dense-mode for all multicast groups is incorrect because the mode is adaptive, not fixed.

• ✗

  The router will only support IGMPv2, and IGMPv3 queries will be ignored.

  Why it's wrong here

  Configuring IGMPv2 on an interface means the router sends IGMPv2 membership queries, but it does not ignore IGMPv3 reports; the router may still process these reports, though source-specific join and leave information is not fully understood. The issue is not that IGMPv3 queries are ignored — hosts do not send queries, the router is the querier. To fully support IGMPv3 group and source filtering, you must explicitly configure "ip igmp version 3" on the interface.

• ✓

  Multicast routing is enabled with distributed switching, and the interface will use sparse-mode if an RP is known for the group, otherwise dense-mode.

  Why this is correct

  The command "ip multicast-routing distributed" enables multicast routing in global configuration and, on supported distributed platforms, enables CEF-based multicast forwarding using the Multicast Forwarding Information Base (MFIB) on line cards. Combined with "ip pim sparse-dense-mode" on an interface, the router will initially send PIM joins or use dense-mode behavior depending on whether an RP is known for a given multicast group; if an RP is known (static, BSR, or Auto-RP), sparse-mode is used, otherwise the group operates in dense-mode. This is the correct interpretation of both the command and PIM mode behavior.

• ✗

  The configuration is invalid because 'ip multicast-routing distributed' is not a valid command.

  Why it's wrong here

  The statement that the command is invalid is false; "ip multicast-routing distributed" is a valid global configuration command on many Cisco IOS-XE platforms and is required for distributed multicast forwarding on platforms with multiple line cards or route processors. It enables multicast routing and enables MFIB distributed switching, allowing multicast RIB and FIB entries to be populated on all forwarding engines. While some low-end platforms may not accept the "distributed" keyword, on supported platforms it is a perfectly valid command, not a configuration error.