[23443] in North American Network Operators' Group
Re: FEC (Fast Etherchannel) issues
daemon@ATHENA.MIT.EDU (Danny McPherson)
Thu Mar 18 18:40:18 1999
To: nanog@merit.edu
From: Danny McPherson <danny@qwest.net>
Reply-To: danny@qwest.net
Date: Thu, 18 Mar 1999 16:37:08 -0700
Errors-To: owner-nanog-outgoing@merit.edu
>
> This looks kinda like the right place for this issue, apologies if not:
Cisco NSP or the like probably would have been more appropriate.
> True or False?
>
> FEC (Fast EtherChannel) is not suibtable for router to router trunking
> because of the way FEC load balances
Depends.
> I've heard and read in various places (although nothing conclusive) that
> since FEC uses the last portion of a MAC address and hashs it to determine
> which 100 meg link a packet goes. This is to prevent packets from
> arriving on the other end out of order.
Only brand 'C' switches do the MAC hash thing, the routers do things with
"microflows" (unless per-packet stuff is enabled).
> This would seem to suggest that FEC wouldn't work between routers or
> similar layouts because there is only one MAC address on either end,
> therefor packets would always go over the same link.
Yes, between a given set of routers .. if you have brand 'C' switches in the
middle.
> Anybody have concrete details on this issue? Does FEC actually determine
> load balancing this say? is ther another way to configure this?
Don't put switches in the middle?
-danny
