Routes Selection

Thu Oct 7 11:42:39 UTC 2004

Hi,

Given two routes similar in preference (BGP steps) where each is
received from a different ISP (or technically speaking an AS). How do
I as a network operator decide which one to install in the forwarding
table?

Here goes the list of options that i have:

(a) I can install both the routes in my FIB and split the traffic.
Packet reordering would not be a problem as most of the modern routers
hash packets based on the fields carried in the IP header. Thus
similar packets would flow in same direction. OAM can be a minor
issue. But its not something that is impossible to sort out. People
have been anyway doing it for IGPs.

(b) I could select one route based on *some* policy. I would love to
get an insight on what kind of policies people use to route traffic.
Now, I use just one route. The other comes live into action when the
primary or my first one goes down. I get redundancy but I lose
bandwidth. To save bandwidth I could write policies/routemaps/etc to
send some traffic over one link and the remaining over the other. But
then this is static and does not guarantee an equal or a just split of
traffic.

Any help/comments on this would be highly appreciated.

Regards,
Abhishek V.

--
Class of 2004
Institute of Technology, BHU
Varanasi, India