Multicast IGMP Snooping Troubleshooting Commands
You can use the commands in this section to troubleshoot problems related to multicast IGMP snooping.
Displays if 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, the show cdp neighbor command will not display any information.
Example 19-1 show cdp neighbor Command
switch# 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
switch Eth3/2 179 R S I WS-C6506-E Gig5/16
switch Eth3/4 179 R S I WS-C6506-E Gig5/23
Displays whether IGMP snooping is enabled on the VLAN.
Example 19-2 show ip igmp snooping vlan Command
switch# 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
- show ip igmp snooping groups
switch# show ip igmp snooping groups vlan 1784
Type: S - Static, D - Dynamic, R - Router port
Vlan Group Address Ver Type Port list
1784 */* - R Po1 Po2 Eth5/31
1784 227.0.0.1 v2 D Veth79 Veth80
VSM-DAO# show ip igmp snooping querier vlan 1784
Vlan IP Address Version Expires Port
1784 184.184.0.12 v3 00:04:14 Po1
1784 184.184.0.12 v3 00:04:14 Po2
1784 184.184.0.12 v3 00:04:14 Eth5/31
switch# show ip igmp snooping groups vlan 1784 detail
IGMP Snooping group membership for vlan 1784
Group ver: v2 [old-host-timer: not running]
report-timer: not-running
Last reporter: 184.184.0.11
switch# show ip igmp snooping groups vlan 1784 summary
Legend: E - Enabled, D - Disabled
Total number of (*,G) entries: 2
Example 19-3 debug ip igmp snooping vlan Command
switch(config)# debug ip igmp snooping vlan
2014 Jul 8 23:49:16.633077 igmp[3157]: SNOOP: Switchport interface Veth43 (308) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:16.683929 igmp[3157]: SNOOP: Switchport interface Veth37 (128) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:16.748355 igmp[3157]: SNOOP: <vlan 1> clear port:Veth43, vlan:1
2014 Jul 8 23:49:16.789832 igmp[3157]: SNOOP: Switchport interface Veth47 (428) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:16.797079 igmp[3157]: SNOOP: Switchport interface Veth38 (158) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:16.824702 igmp[3157]: SNOOP: <vlan 11> Added Veth43 to active ports for vlan 11
2014 Jul 8 23:49:16.824854 igmp[3157]: SNOOP: Mode for if(Vethernet43): 0x80000 vlan: 11
2014 Jul 8 23:49:16.862531 igmp[3157]: SNOOP: <vlan 1> clear port:Veth37, vlan:1
2014 Jul 8 23:49:16.950490 igmp[3157]: SNOOP: <vlan 11> Added Veth37 to active ports for vlan 11
2014 Jul 8 23:49:16.950638 igmp[3157]: SNOOP: Mode for if(Vethernet37): 0x80000 vlan: 11
2014 Jul 8 23:49:16.998800 igmp[3157]: SNOOP: <vlan 1> clear port:Veth38, vlan:1
2014 Jul 8 23:49:16.999030 igmp[3157]: SNOOP: <vlan 1> clear port:Veth47, vlan:1
2014 Jul 8 23:49:17.089056 igmp[3157]: SNOOP: Switchport interface Veth40 (218) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:17.121007 igmp[3157]: SNOOP: Switchport interface Veth39 (188) has been created, obtaining any static mrouter/oif configs
2014 Jul 8 23:49:17.131549 igmp[3157]: SNOOP: <vlan 11> Added Veth38 to active ports for vlan 11
2014 Jul 8 23:49:17.131693 igmp[3157]: SNOOP: Mode for if(Vethernet38): 0x80000 vlan: 11
2014 Jul 8 23:49:17.156004 igmp[3157]: SNOOP: <vlan 11> Added Veth47 to active ports for vlan 11
Note Even if you enable the debug command for IGMP snooping, log details are not available for multicast groups and their members.
Example 19-4 module vem module-number execute vemcmd show vlan Command
switch# module vem 3 execute vemcmd show vlan 159
BD 159, vdc 1, vlan 159, 3 ports
Group 224.1.2.3 RID 1 Multicast LTL 4408
Group 0.0.0.0 RID 2 Multicast LTL 4407
On the VSM, use the following command:
- module vem 3 execute vemcmd show igmp 1784
In Example 19-2, global IGMP snooping is enabled on VLAN 1784 (the disabled global state takes precedence)
Multicast group table values are as follows:
Group 227.0.0.1, Multicast LTL: 10363
Group */*, Multicast LTL: 10358
- module vem 3 execute vemcmd show igmp 1784 de
In Example 19-2, global IGMP snooping is enabled on VLAN 1784 (the disabled global state takes precedence)
Multicast group table values are as follows:
Group 227.0.0.1, Multicast LTL: 10363
Members: 59, 1039
Group */*, Multicast LTL: 10358
Members: 1039
Querier Info -
IP Address: 184.184.0.12
Uptime: 241955 seconds
Version: 3
Timeout: 8 seconds
- module vem module-number execute vemcmd show vlan
In Example 19-4, the output shows that LTL 18 corresponds to vmnic3, and LTL 47 corresponds to VM fedora8, interface eth0.
The multicast group table for 224.1.2.3 shows the interfaces that the VEM forwards to when it receives multicast traffic for group 224.1.2.3. If fedora8 has multicast group 224.1.2.3 on its eth0 interface, LTL 47 should be in the multicast group table for 224.1.2.3.
LTL 18 is also in multicast group 224.1.2.3, which means it is a VM and generates multicast traffic to 224.1.2.3. The traffic is 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 multicast group, the address uses the default route, which means that the traffic is forwarded to an upstream switch through vmnic3.