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I am using a centos 6.3 server to subscribe to UDP multicast data and I noticed that my server doesn't answer to the IGMP queries sent by the switch it is connected to.

As a result, when I open my multicast socket I start receiving multicast data but this stops when my IGMP subscription timeout. The server doesn't renew its IGMP subscriptions so the switch cut us off. (To insure that the problem doesn't comes from any code of mine, I am simply using smcroute to open multicast subscriptions)

I searched online for a while and none of the tips I found helped me to fix this problem.

Here is an screenshot of the IGMP communications on any interface of my server:

http://img521.imageshack.us/img521/9953/capture10y.png

As we can see, my server first send 2 IGMP joins but a few minutes after, when the switch send IGMP query, nobody answers.

The version of the IGMP protocol set for the concerned interface is V2:

[root@localhost ~]# cat /proc/net/igmp
Idx Device    : Count Querier   Group    Users Timer    Reporter
1   lo        :     0      V2
                010000E0     1 0:00000000       0
2   eth0      :     5      V2
                FB0000E0     1 0:00000000       1
                010000E0     1 0:00000000       0
5   tap0      :     5      V3
                FB0000E0     1 0:00000000       0
            010000E0     1 0:00000000       0
7   eth1.371:    13      V2
            414000E0     1 0:00000000       1
            404000E0     1 0:00000000       1
            3F4000E0     1 0:00000000       1
            504000E0     1 0:00000000       1
            524000E0     1 0:00000000       1
            494000E0     1 0:00000000       1
            4A4000E0     1 0:00000000       1
            4B4000E0     1 0:00000000       1
            FB0000E0     1 0:00000000       0
            010000E0     1 0:00000000       0

The rp_filter is disabled on this interface:

[root@localhost ~]# cat /proc/sys/net/ipv4/conf/eth1.371/rp_filter 
0
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