[c-nsp] BGP Question - Upstream

[David Luyer]

1.  Prepend to all the other upstreams to equal up the path length
    and have your other upstreams prepend out to you as well

2.  There is a non-Cisco router[1] which will basically "remove-private-as"
    a public AS.  But it is an ugly solution and requires support from
    both the direct upstream (to strip their AS from the path) and
    the tier 1 (to disable AS path validation "no bgp enforce-first-as"
    is required).  If its only inbound AS paths that matter then its
    the direct upstream who need to be able to strip the AS and you who 
    needs to "no bgp enforce-first-as".

3.  Combine #1 and #2;

		outbound, prepend to upstreams other than this one by one

		inbound, get direct upstream to not add their own AS to
		any paths which transit their AS, and disable
enforce-first-as
		on your router

4.  eBGP multihop to the tier 1 (requires, again, support from the tier 1,
    and static routes to ensure the multihop doesn't pass over the wrong
    path)

5.  Cut out the middle man :-)

#1 and #5 are the real solutions.

David.

[1] at least I'm not aware of any IOS version which can do this but
    I've seen it done in a Foundry.  It would be trivial to make
    IOS able to do it if you could find someone with code access :)

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Paul Stewart
> Sent: Monday, 7 March 2005 1:22 PM
> To: Paul Stewart
> Cc: cisco-nsp at puck.nether.net
> Subject: [c-nsp] BGP Question - Upstream
> 
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> 
> Hi there..
> 
> We have a particular upstream that is basically a relay to us for a Tier
> 1 provider.. they have their own AS so when we go out/in from the Tier 1
> provider there is an additional AS in our way (the upstream)...
> 
> Our other providers are Tier1 so we don't encounter this extra AS hop.
> Is there a way around this?  A trick of the trade? ;)
> 
> We do prepending and weighting etc already and was hoping to have a more
> "natural" take on this...  the problem is that the other providers who
> are Tier1 directly to us appear much more attractive all the time
> because of less hops...
> 
> Anyways, if anyone has any ideas that would be great.. along with
> pros/cons of suggestions...
> 
> Thanks,
> 
> Paul
> 
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