IGMPv2 : specific-query vs all group query

[parisdooz12]

Hi,

Is it a way in IOS (in my case, 12.2(33)SXI) to force the IGMP querier to perform Specific-Queries?

I have indeed in my network several multicast flows; as I monitor the RP paquets, I can see the queries still use the IP address 224.0.0.1 as destination, and not the specific-query?

Thanks in advance

P.

[cadet alain]

Hi,

is the interface using IGMPv2 ---> sh ip igmp interface

if not then set it --->  ip igmp version 2  it is the default but it may have been set to v1

even if it is still v2 the specific-query will only be when it receives a leave message from a host.

Regards.

Alain.

[parisdooz12]

Ok, thanks. It misunderstood the IGMPv2 mecanism and was sure that the general query was no more used in IGMPv2.

Actually, I find that a bit strange as a host should send several unsollicited report messages when it want to join a group. So the router should know all group memberships and so, it shouldn't need to send general query (at least if all hosts connected to the interface are IGMPv2 compatible)

Regards

P.

[Peter Paluch]

Hello,

So the router should know all group memberships and so, it shouldn't  need to send general query (at least if all hosts connected to the  interface are IGMPv2 compatible)

Not entirely, for the following reasons:

• IGMP messages are not acknowledged nor transmitted reliably, and they may get lost. Asking generally for all group memberships allows to work around this problem.
• Group memberships expire after a certain time period. Renewing group memberships periodically is more effective using a single general Membership Query, instead of asking for each and every group using a group-specific Membership Query. In addition, using only group-specific Membership Query would prevent the router from learning about group memberships in new groups it does not yet know about.

Best regards,

Peter

[parisdooz12]

ok. Many thanks for these explanations.

Regards,

P.