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Muticast problem, Need help on the one!


My distribution router are cat 6509-SUP720-PFC3A. One of my distribution bloc is giving access to many small building over fiber link. In each building, I have a pair of 4912G serving as building root(SPT also). They are connected together and access switch(3500XL or 3750) are connected to each of them.

My problem is that I'm not receiving any IGMP Query from the PIM-DR on ->ONE<- vlan. If I change the vlan of the port, it work's!. The config of the vlans interfaces on the two router is the same.

The router debug tell my that it's sending the query. If I sniff the host, it's receiving the data but never the query. The session timeout after 2-3 minutes. This is the only vlan with this problem.


Re: Muticast problem, Need help on the one!

Hello Dominic,

Have you checked if the IGMP snooping is enabled for that VLAN? I have seen many application fail because intermediate switches blocked propagation of IGMP query/join messages.

The fact that another VLAN is capable of receiving and sending IGMP query/join messages makes this doubtful. Can't harm to check it though.

Switch# show ip igmp snooping vlan x



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Re: Muticast problem, Need help on the one!

The L2 switch are configure ok...cmgp or igmp.

I have two possible suspect...a host on the vlan is causing this or the L2 part of the SUP720 is not doing it's job. How do I troubleshoot the L2-SUP720

Community Member

Re: Muticast problem, Need help on the one!

I think SW does not work IGMP snooping, or does not know where IGMP query is from. i suggest you enable IGMP snooping or specify IGMP source IP address.


Switch(config)#ip igmp snooping querier ?

address IGMP querier source IP address

max-response-time IGMP querier maximum response time (sec)

query-interval IGMP querier query interval (sec)

tcn IGMP querier TCN related parameters

timer IGMP other querier timer

version IGMP version

Re: Muticast problem, Need help on the one!

Here is my interface configuration

interface Vlan82

description (FFG) Sciences giomatique Casault (diligui)

ip address X.X.82.2

ip access-group 171 in

no ip redirects

no ip unreachables

no ip proxy-arp

ip pim dr-priority 10

ip pim sparse-mode

ip cgmp

standby 10 ip X.X.82.1

standby 10 timers 1 4

standby 10 priority 200

standby 10 preempt delay minimum 10

standby 10 track Port-channel13 75

standby 10 track Port-channel15 75


CSLDKNA#sh ip igmp snooping mrouter vlan 82

vlan ports


82 Po117,Router

Vlan82 is up, line protocol is up

Internet address is x.x.82.2/24

IGMP is enabled on interface

Current IGMP host version is 2

Current IGMP router version is 2

CGMP is enabled on interface

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: 58 joins, 57 leaves

Multicast routing is enabled on interface

Multicast TTL threshold is 0

Multicast designated router (DR) is X.X.82.2 (this system)

IGMP querying router is X.X.82.2 (this system)

No multicast groups joined by this system

IGMP snooping is globally enabled

IGMP snooping is enabled on this interface

IGMP snooping fast-leave (for v2) is disabled and querier is disabled

IGMP snooping explicit-tracking is enabled

IGMP snooping last member query response interval is 1000 ms

IGMP snooping report-suppression is enabled

Re: Muticast problem, Need help on the one!

Should I do

ip igmp joint-group x.x.x.x

ip igmp snooping static xxxx.xxxx.xxxx int poXXX

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