[c-nsp] C3845 not processing IGMP reports

Rodney Dunn rodunn at cisco.com
Wed Jun 27 12:21:21 EDT 2007


I'd have to check the IGMP spec...what does (in text) the
actual IGMP report look like?

Where did you capture it? Make sure you span the port going
to the router.

Rodney

 
On Wed, Jun 27, 2007 at 03:55:04PM +0300, Matti Saarinen wrote:
> 
> What could be causing the following problem with Cisco 3845 and IGMP
> reports?
> 
> We've got a 3845 running 12.4(13a) which appears not to process IGMP
> reports which are sent to it. The host is sendind IGMP reports for a
> group (tcpdump shows them) but the 3845 doesn't see them according to
> the output from debug ip igmp. The IGMP queries sent by the router are
> seen by the host. Also, when the host sends an IGMP leave packet the
> router sees it. 
> 
> The subnet the host belongs to is connected to a GE sub interface which
> is dot1q tagged. There is a HP 5308 between the host and 3845 but it
> isn't processing IGMP at all.
> 
> Below is some config info:
> 
> c3845#show run int gi0/1.180
> [...]
> interface GigabitEthernet0/1.180
>  description nnnn
>  encapsulation dot1Q 180
>  ip address x.x.x.x
>  ip helper-address y.y.y.y
>  ip helper-address z.z.z.z
>  ip pim sparse-mode
> end
> 
> c3845#sh ip multicast interface gi0/1.180
> GigabitEthernet0/1.180 is up, line protocol is up
>   Internet address is x.x.x.x/24
>   Multicast routing: enabled
>   Multicast switching: fast
>   Multicast packets in/out: 4/92094
>   Multicast TTL threshold: 0
>   Multicast Tagswitching: disabled
> 
> 
> Cheers,
> 
> -- 
> - Matti -
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