IGMP - Layer 2 or Layer 3

dppagc

From what I read from books,

IGMP is communication from host to router - is it a L2 to L3 communication?

But IGMP snooping occurs at the L2 switch. So I assumes that it intercepts the frames?

OfWolfAndMan

Technically Layer 3. There is no transport layer used in an IGMP packet.
IGMP snooping is a layer 2 concept though, yes. IGMP in regards to forwarding logic is technically layer 2 yes as the message is local to the LAN and membership queries are only sent to the LAN. HOWEVER, structurally speaking, IGMP messages are sent in IP data grams with a TTL set to 1, so they can't leave the LAN, but they are encapsulated at Layer 3.

Here is a captured frame for your reference. Hope this helps.

Screen Shot 2015-12-29 at 10.58.48 PM.jpg