More ramblings from the annoying route engine guy...

Joshua Coombs jcoombs at
Thu Oct 21 12:02:25 PDT 2004

> I think this functionality is called ``etherchanneling'' and it is
> provided on a lot of routers.

etherchannel is a means of bonding two or more ethernet point to 
point links to simulate a larger single 'link'.  Its limited in that 
all links must start and end on the same two pieces of equipment, so 
while it protects against loosing one channel, it doesn't offer 
diverse paths out through multiple end nodes.  I believe getting 
more specific 'Fast Etherchannel' is Cisco's implimentation, there 
is a newer, RFC'd version that supercedes it out in the wild.

> It sounds cool to me, but it's not really similar to CARP or VRRP, 
> where, for instance, if one machine goes down, another takes over. 
> I think these two could certainly work hand-in-hand; assume two 
> routers which are etherchanneling, one goes down and the other 
> takes over.

Virtualzing the interfaces wouldn't replicate VRRP/CARP, but it 
would make the concept lighter.  The work of dealing with arping for 
an ip on a specific interface under x/y/z conditions would be a 
handy side effect of this setup.  Your carp daemon just toggles the 
bind between the virtual interface and a real physical interface as 
needed.  (Just one example.)

Joshua Coombs
aka Kurlon for those looking for me on IRC 

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