etherchannel & portfast of STP

dissolved

portfast brings an interface right up, instead of going through blocking, learning etc..

dshevnock

An etherchannel is a logical bundaling of ethernet trunks that run between two different switches. Let say that you have 5 trunks running between 2 switches. If you group all 5 of those trunks into an etherchannel, the switch will see that 1 logical etherchannel link instead of the 5 physical trunk link. The advantage of this are:

- if one of the physical links goes down, the switch will never know and STP won't have to be run. (which in turn you don't have the 50 second delay when a link goes down and STP switched ports from blocking to forwarding states)

- throughput is much higher through the one logical etherchannel link, then it is through 5 seperate physical links. The traffic of the 5 trunks will be shared through the one etherchannel.

If you set a port on a switch to be portfast, that port will never go through the blocking to forwarding states that STP distinguishes (it is always in a forwarding state until administratively changed). Portfast should generally only be run when end-user devices are connected to that specific port. If you run portfast on a port conncted to a router, switch, bridge, etc., you leave your network wide open for switching loops.

Hope this helps...

rossonieri#1

etherchannel is a way to provide more bandwidth available to use (2 ports 100mbps join together eq. 200mbps output) by adding more ports in trunking mode.
in nortel term they call it MLT = multi link trunks.