To troubleshoot issues with multicast IGMP snooping, use the following commands:
You can use the
show cdp neighbor
command because IGMP uses the packet VLAN to forward IGMP packets to the VSM, which is the same mechanism that CDP uses. However, if you have disabled the CDP protocol on the upstream switch using the
no cdp enable
command, then the
command will not display any information.
show cdp neighbor Command
n1000V# show cdp neighbor Capability Codes: R - Router, T - Trans-Bridge, B - Source-Route-Bridge S - Switch, H - Host, I - IGMP, r - Repeater, V - VoIP-Phone, D - Remotely-Managed-Device, Device ID Local Intrfce Hldtme Capability Platform Port ID n1000V Eth3/2 179 R S I WS-C6506-E Gig5/16 n1000V Eth3/4 179 R S I WS-C6506-E Gig5/23
Use the show ip igmp groups command to make sure IGMP snooping is enabled on the VLAN.
Example 18-2 show ip igmp snooping vlan Command
n1000V# show ip igmp snooping vlan 159 IGMP Snooping information for vlan 159 IGMP snooping enabled <-- IGMP SNOOPING is enabled for vlan 159 IGMPv3 Explicit tracking enabled (initializing, time-left: 00:03:20) IGMPv2 Fast leave disabled IGMPv1/v2 Report suppression enabled IGMPv3 Report suppression disabled Router port detection using PIM Hellos, IGMP Queries Number of router-ports: 0 Number of groups: 0show ip igmp snooping
show ip igmp snooping groups
debug ip igmp snooping vlan
Example 18-3 debug ip igmp snooping vlan Command
n1000V(config)# debug ip igmp snooping vlan 2008 Sep 2 13:29:36.125661 igmp: SNOOP: <vlan 159> Process a valid IGMP packet 2008 Sep 2 13:29:36.126005 igmp: SNOOP: <vlan 159> Received v2 report: group 126.96.36.199 fro 188.8.131.52 on Vethernet3 2008 Sep 2 13:29:36.126086 igmp: SNOOP: <vlan 159> Added oif Vethernet3 for (*, 184.108.40.206) entry 2008 Sep 2 13:29:36.126157 igmp: SNOOP: <vlan 159> Forwarding report for (*, 220.127.116.11) came on Vethernet3 2008 Sep 2 13:29:36.126225 igmp: SNOOP: <vlan 159> Forwarding the packet to router-ports 2008 Sep 2 13:29:36.126323 igmp: SNOOP: <vlan 159> Forwarding packet to router-port Ethernet3/6 (iod 42)
On the VSM, use the following command:
execute vemcmd show vlan
In Example 18-4, the output shows that LTL 18 corresponds to vmnic3, and LTL 47 corresponds to VM fedora8, interface eth0.
The multicast group table for 18.104.22.168, shows the interfaces the VEM will forward to when it receives multicast traffic for group 22.214.171.124. If fedora8 has multicast group 126.96.36.199 on its eth0 interface, then LTL 47 should be in the multicast group table for 188.8.131.52.
LTL 18 is also in multicast group 184.108.40.206, which means it is a VM and generates multicast traffic to 220.127.116.11. The traffic will be forwarded to vmnic3, which is the uplink to the upstream switch.
The multicast group table entry for 0.0.0.0 serves as a default route. If any multicast group traffic does not match any of the multilcast group, the address will use the default route, which means, in this case, that the traffic will be forwarded to an upstream switch through vmnic3.
Example 18-4 module vem
vemcmd show vlan Command
n1000V# module vem 3 execute vemcmd show vlan 159 BD 159, vdc 1, vlan 159, 3 ports Group 18.104.22.168 RID 1 Multicast LTL 4408 Group 0.0.0.0 RID 2 Multicast LTL 4407