Layer 2 / Layer 3 Cascading

[asfar.zaidi]

Hi Guys

Can anybody explain me what is layer 2 and layer 3 cascading of 3750-G Switches.

The reason I am asking that we are in phase of implementing Multicast for IPTV and the vendor requirements are as follows:

1. Edge devices can be layer 2 devices which support IGMP snooping (this allows switches to only forward multicast traffic to the ports that actually want the traffic and not to all of them

2. No cascading between layer 2 devices: it means that Layer 2 edge CANNOT be connected to another Layer 2 switch. Layer 3 cascading is fine.

My Edge devices are Cisco 3750G Switches. Please also brief me what I need to do to fullfill vendor's requirement.

Regards/Asfar

[asfar.zaidi]

Oops............. Guys Nobody to Answer my Question

[Joseph W. Doherty]

Sounds like they don't want one L2 switch to connect to another L2 but L3 to L3 is fine, along with L3 to L2.

Your 3750G switches are L3 switches, so even at the edge you can run them just as L2 or use them as L3. (Stacking them, via 3750 stack cables, I suspect, probably has nothing to do with cascade restrictions.)

If you connect your 3750G uplink to another L3 device, and don't connected multiple 3750G edge devices directly to each other except via the special stack cable (if more than one), then you should be fine as long as you also configure IGMP snooping for your edge VLANs.

You didn't ask about multicast routing, so I assume you understand that.