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| 7.3 |  | Routing Multicast Traffic |
| 7.3.12 |  | Verify PIM configuration |

To display information about interfaces configured for PIM, enter the following command in EXEC mode.

> Router#show ip pim interface [type number] [count]

The results of this command display the following items:

- IP address of the next-hop router
- The interface type; on an RSM, this value will be the VLAN designation
- The PIM mode configured on each interface
- Number of PIM neighbors that have been discovered through this interface
- Frequency, in seconds, of PIM router-query messages
- IP address of the designated router on the LAN

Select a Designated Router
Cisco routers use the PIM routing protocol to forward multicast traffic. Two PIM routers are neighbors if there is a direct connection between them.

Each multicast-enabled router is configured to know which interfaces will be using PIM. These interfaces connect either to neighboring PIM routers in the network or to host systems on a LAN. If there are multiple PIM routers on a LAN, they are considered to be neighbors.

The procedure for electing the designated router (DR) is the same for both PIM SM and PIM DM. Each PIM router connected to a multiaccess LAN issues periodic PIM router queries onto the LAN. The PIM router with the highest IP address becomes the DR for the LAN. If the DR becomes inoperable, a new DR is elected from the alternate PIM routers on the LAN.

> Note: DR election is necessary only on multiaccess networks. It is not required for point-to-point links because the connected router is effectively the DR for directly connected host systems.

On a multiaccess LAN, one router is selected to poll the LAN for host group membership. However, all PIM routers on a single subnet receive replies from the host. The router selected to poll the LAN is called the DR. The DR is responsible for sending IGMP host-query messages to all hosts on the LAN. There can be many DRs in a campus network, one for each leaf subnet of the distribution tree.

Display a PIM Neighbor
The Cisco IOS Software can be used to discover the PIM neighbors in the network. To display a table of the neighboring routers from a specific router, enter the following command in privileged EXEC command mode.

> Router#show ip pim neighbor type number