[c-nsp] C3845 not processing IGMP reports

[Matti Saarinen]

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 -