North American Network Operators Group

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Re: FEC (Fast Etherchannel) issues

  • From: Kevin Brown
  • Date: Fri Mar 19 19:28:39 1999

Although I am by no means the authority on how FEC works, I do understand
the technology at issue.

Cisco's implementation of FEC uses the X-OR (exclusive-OR) algorythm, and
examines the last two bits of the source and destination MAC addresses.  In
doing this, there will be one of four possible results ( 01, 00, 11, 10 ).
Each of these possible results are mapped to a bundled link.

In your case, since you say you are doing this between routers, and your
requirement seems to be load balancing between links, then I would suggest
using a layer 3 routing protocol like OSPF that will automatically load
balance between links with the same administrative cost.

Again, I don't consider myself the man with all the answers, but if you are
doing this between routers, then I would most definately keep my load
balancing in the L3 arena, especially when it could be from a
standards-based routing protocol rather than a quasi-proprietary protocol.

My 2 cents,

Kevin Brown
Sr. Data Systems Engineer
Sprint - BMO - JCMO

## nothing I say is to be considered the position of my employer.  so there!