350-401 Practice Question: Given the following partial configuration on a…

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 router will use 10.0.0.1 as the RP for all multicast groups from 224.0.0.0 to 224.255.255.255, and the interface will operate in sparse-mode.

  Why this is correct

  The command 'ip pim rp-address 10.0.0.1 10' associates ACL 10 with the static rendezvous point (RP) address for the entire 224.0.0.0/8 group range, since ACL 10 matches all addresses from 224.0.0.0 to 224.255.255.255. When an interface is configured with 'ip pim sparse-mode', it joins the PIM sparse-mode domain, where multicast forwarding relies on an RP for group registration and shared-tree construction. Because the ACL explicitly includes the full 224.0.0.0/8 range, the router will indeed use 10.0.0.1 as the RP for all groups in that range, and the interface operating in sparse-mode will actively use this RP to build the rendezvous point tree (RPT).

• ✗

  The router will ignore the static RP because the ACL includes the reserved link-local range (224.0.0.0/24).

  Why it's wrong here

  The router does not automatically exclude or ignore the reserved link-local multicast range (224.0.0.0/24) when it is matched by the ACL used in the static RP configuration. The ACL simply defines a group prefix range, and since the ACL includes the entire 224.0.0.0/8, the static RP will apply to link-local groups as well, even though those groups are normally not forwarded or PIM-registered due to their TTL and link-local scope. In practice, this is considered a misconfiguration because PIM is unnecessary for on-link, link-local multicast, but the router will still attempt to use the RP, so the claim that it 'ignores' the RP is factually wrong.

• ✗

  The interface must also be configured with 'ip pim dense-mode' for the RP to work.

  Why it's wrong here

  PIM dense-mode and sparse-mode are mutually exclusive operational modes; an interface cannot be both. Dense-mode uses a flood-and-prune behavior that does not require an RP, whereas sparse-mode builds a shared tree via an RP and is the mode required for RP-based multicast. Adding 'ip pim dense-mode' to the interface would actually prevent the static RP configuration from being used, because dense-mode has no RP mechanism. Therefore, the interface must be in sparse-mode (or sparse-dense-mode with careful logic) for the RP to function; additional dense-mode configuration is not needed and would be counterproductive.

• ✗

  The RP address 10.0.0.1 must be configured on a loopback interface on the same router.

  Why it's wrong here

  The static RP address in the 'ip pim rp-address' command does not have to be a loopback interface on the same router; it can be any reachable IP address in the network. The RP is simply a router that hosts the rendezvous point function, and it is common for the RP to be on a different router entirely. While best practice often recommends making the RP a loopback interface on the RP router for stability and reachability, there is no requirement that the RP be local to the router issuing the command. Thus, the claim that 10.0.0.1 must be a loopback on the same router is incorrect.

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