Troubleshooting Multicast Routing
When troubleshooting for information about the multicast routing protocol, first use the show ip pim command, which requires an additional option before providing information. The following shows the major options available, from interfaces to RPs to neighbors:
Router2>enable Password: Router2#show ip pim ? autorp Global AutoRP information bsr-router Bootstrap router (v2) interface PIM interface information mdt Multicast tunnel information neighbor PIM neighbor information rp PIM Rendezvous Point (RP) information rp-hash RP to be chosen based on group selected vrf Select VPN Routing/Forwarding instance
Sparse mode PIM has several requirements for RPs on the network. So, if you are in Sparse mode, you want to take a close look at the several RP-based options. In addition, reviewing neighbors is always important, because if you do not see any neighbors, you probably have significant issues with the protocol implementation. Output about neighbor and rp look like the following; notice particularly the version and rp information:
Router2>enable Password: Router2#show ip pim neighbor PIM Neighbor Table Neighbor Interface Uptime/Expires Ver DR Address Prio/Mode 192.168.1.2 FastEthernet0/0 00:02:16/00:01:26 v2 1 / S Router2#show ip pim rp Group: 18.104.22.168, RP: 192.168.1.2, v2, uptime 00:06:13, expires never Group: 22.214.171.124, RP: 192.168.1.2, v2, uptime 00:05:58, expires never Group: 126.96.36.199, RP: 192.168.1.2, v2, uptime 00:06:15, expires never Group: 188.8.131.52, RP: 192.168.1.240, v2, v1, next RP-reachable in 00:00:31 Group: 184.108.40.206, RP: 192.168.1.240, v2, v1, next RP-reachable in 00:00:31
Also, much of the multicast routing involves requests from client devices via IGMP requests from the specific receiving devices that are connected to your network switches. To see that data, use one of the following commands:
Router2>enable Password: Router2#show ip igmp ? groups IGMP group membership information interface IGMP interface information membership IGMP membership information for forwarding snooping Snooping info on Catalyst Vlans ssm-mapping Display IGMP SSM mapping info tracking IGMP Explicit Tracking information udlr IGMP undirectional link multicast routing information vrf Select VPN Routing/Forwarding instance
Within the IGMP data are groups, interfaces, and membership, and although you may find that these options are the most important ones, it is recommended that you test all the options to see exactly what is going on.
In the following output, the groups option shows you the addresses for which the router is routing, as well as when the membership expires (because this is Sparse mode data), interface shows statistical information for the interface, and membership shows addresses or groups, who is subscribing to those addresses, and the interface on which they are working.
Router2>enable Password: Router2#show ip igmp groups IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter 220.127.116.11 FastEthernet0/0 00:08:22 00:02:07 192.168.1.103 18.104.22.168 FastEthernet0/0 00:06:22 00:02:07 192.168.1.2 22.214.171.124 FastEthernet0/0 00:08:24 00:02:10 192.168.1.240 126.96.36.199 FastEthernet0/0 00:08:21 00:02:13 192.168.1.10 188.8.131.52 FastEthernet0/0 00:08:23 00:02:09 192.168.1.10 Router2#show ip igmp interface FastEthernet0/0 is up, line protocol is up Internet address is 192.168.1.240/24 IGMP is enabled on interface Current IGMP host version is 2 Current IGMP router version is 2 IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Last member query count is 2 Last member query response interval is 1000 ms Inbound IGMP access group is not set IGMP activity: 5 joins, 0 leaves Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 192.168.1.240 (this system) IGMP querying router is 192.168.1.2 Multicast groups joined by this system (number of users): 184.108.40.206(1) Router2#show ip igmp membership Flags: A - aggregate, T - tracked L - Local, S - static, V - virtual, R - Reported through v3 I - v3lite, U - Urd, M - SSM (S,G) channel 1,2,3 - The version of IGMP the group is in Channel/Group-Flags: / - Filtering entry (Exclude mode (S,G), Include mode (*,G)) Reporter: <mac-or-ip-address> - last reporter if group is not explicitly tracked <n>/<m> - <n> reporter in include mode, <m> reporter in exclude Channel/Group Reporter Uptime Exp. Flags Interface *,220.127.116.11 192.168.1.103 00:09:40 02:52 1A Fa0/0 *,18.104.22.168 192.168.1.2 00:07:41 02:53 2A Fa0/0 *,22.214.171.124 192.168.1.103 00:09:42 02:54 1LA Fa0/0 *,126.96.36.199 192.168.1.10 00:09:39 02:57 2A Fa0/0 *,188.8.131.52 192.168.1.31 00:09:41 02:49 2A Fa0/0