IGMP Snooping

Hi Mungi,

Cheap switches (anything you can buy new for 20-30 USD) are only designed to learn MAC addresses, build a MAC address table and forward Ethernet frames based on the destination MAC address. That’s it.

These switches are unable to look into the content of an Ethernet frame to check the payload.

A layer 3 “aware” switch is able to look into the payload and make decisions based on the content, like the IGMP snooping example.

Don’t confuse this with “L3 switches”. There’s a difference between a L3 switch and a L3 “aware” switch. For example, the Cisco catalyst 3560/3750 switches are L3 switches, they can do routing. We also call these “multilayer switches”.

The Cisco 2950 is a L2 switch, it can’t do any routing…it is “L3 aware” though since IGMP snooping is supported. It also supports access-lists.

Hope this helps!