long as path games?

william(at)elan.net william at elan.net
Mon Jan 31 20:24:55 UTC 2005

On Mon, 31 Jan 2005, Christopher L. Morrow wrote:

> > Well, long as-path of 100 is certain to be invalid (result of misconfig if
> just curious, why would it be invalid?

Its invalid in practice. You can build network with as-path larger then 
100 in your lab, but in real world, we do not have this.

Of course you might say that its possible that we have less then 100 
networks and each one is prepending several of their own as# and real 
number of networks is something like 20, but even that is too many and 
each network as-prepending 5 of their own AS is also rather unlikely.

One thing I want to note to cisco and other vendor engineers is that one
easy way to deal with it might be good if there was a way to "cut" number 
of as-prepends - i.e. for long as-path with number of same as## in sequence,
it might be good if router could automaticly cut the number from 10+ to 
say 3 for long as-path, i.e. I'd like to have this available:
 neighbor x.x.x.x max-aspath-sequence 3

Then backbones could set this for their customers and we'll not have these 
long sequences appearing in at-large bgp table. 

William Leibzon
Elan Networks
william at elan.net

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