IGMPv2 and V3 - IGMP_QUERY_VERSION_CONFIGURED_DISCREPANCY: IGMP

[Netmart]

Hello,

I was wondering whether there is any concern or impact expected if for two peering switches running a different IGMP versions when peering with each other:

MCAST Receiver --- cat9400 [LHR]<===>Switch cat6K, IGMPv2 <===> IGMPv3, Core Switch ==>Upstream Interface, RPF Interface, Incoming Interface (IIF)

Extract logs at Core Switch:

Core Igmp: %GMP-4-IGMP_QUERY_VERSION_CONFIGURED_DISCREPANCY: IGMP version 2 query heard on vlan Ethernet1/1 by a querier configured to version 3

According to Cisco:

IGMPv3 is designed to coexist with IGMPv1 and IGMPv2.
IGMPv3 supports all IGMPv2’s IGMP message types and is backward compatible with
IGMPv2. The differences between the two are that IGMPv3 added new fields to the IGMP
membership query and introduced a new IGMP message type called Version 3 membership
report to support source filtering.

source: CCNP and CCIE Enterprise Core ENCOR 350-401 Official Cert Guide, pp.337

Any advice is appreciated.

Thanks

[julian.bendix]

Hey!

Yes, v3 is backwards compatible, forwarding should not be impacted.
The core is simply giving informational messages about receiving v2 messages.

Did you test if everything works? I think it will!

BR Jules

[balaji.bandi]

%GMP-4-IGMP_QUERY_VERSION_CONFIGURED_DISCREPANCY: IGMP version 2 query heard on vlan Ethernet1/1 by a querier configured to version 3

as i remember this is expected Log message when you have different version, 

also can you confirm is the IGMP working ?

[Giuseppe Larosa]

Hello @Netmart ,

if both the cat9400 and the core switch are configured for multicast routing their interaction is done by PIM protocol and not by IGMP that handles receivers.

So you should be safe even if IGMP versions are a mismatch.

Hope to help

Giuseppe

[Netmart]

Thank you Giuseppe.

Yes, from cat9400 and upwards multicast-routing is enabled. IGMP is only used between cat9400 and the receiver.d. So I am wondering what is the reason that cat9400 and above exchange IGMP packets. Is it because IGMP is enabled on those interfaces? If so, should IGMP only enabled from LHR south/downward to the receiver?

Protocol: I GMP                     |   PIM =============>       

MCAST Receiver --- cat9400 [LHR]<===>Switch cat6K, IGMPv2 <===> IGMPv3, Core Switch ==>Upstream Interface, RPF 

[Giuseppe Larosa]

Hello @Netmart ,

IGMP is enabled on interfaces when PIM is enabled by default automatically. 

On a L3 interface a multicast router/switch  can have both PIM neighbors and workstations that answer to IGMP queries.

Hope to help

Giuseppe