L2 vs L3 etherchannel

nel

Hi guys,

first question for you's!!!

whats the difference between L2 and L3 etherchannel? i assume its to do with load balancing? i would just like some clarrification on it as i cant seem to find any doc's for the advantages and disadvantages between the two. When would you use one and then the other? i know how to configure both so thats not the question.

We have the current 6500's in place but it looks like the port-channel is bound to the vlan IP (they both have the same IP) is this possible? i.e vlan 1 could have 192.168.0.1 whilst port-channel 1 could have the same IP? i thought the same would overlap as there separate interfaces?

dtlokee

It's basically the same as the difference between a L3 and a L2 interface on a switch. L2 interfaces can be access ports or trunk ports, will forward boradcasts and send and receive BPDUs. A L3 interface is like a router interface, it will not forward broadcasts and can't carry tagged (trunk) traffic. The L3 etherchannel will show up as a hop in a traceroute. I tyically will use L3 when I don't want to forward broadcasts such as between buildings in a campus or across the WAN, within a building I typically use L2. I find with more and more companies offering some sort of guest access to their network and allowing outside vendor (partner) access it is beneficial to be able to trunk this traffic to the firewall where it is isolated and can be treated as untrusted traffic.

nel

Thanks for the examples dt

mikearama

Damn dt... you should write a book. That was explained better than anything I've read in any ciscopress book.