[c-nsp] Change BGP default-originate to IGP?

[David Prall]

As well could put a GRE Tunnel or VLAN between the two ASR's and run iBGP
between the two. You control the path between the two routers, so the tunnel
can be over a jumbo frame capable path. I would still do a selective
advertisement for the default, so that traffic doesn't need to traverse the
both routers, but this would stop the blackholes for routes unlearned.
Especially if it is the upstream that is having issues, instead of the
direct connection.

David

--
http://dcp.dcptech.com


-----Original Message-----
From: Adam Vitkovsky [mailto:adam.vitkovsky at swan.sk] 
Sent: Thursday, September 27, 2012 4:41 AM
To: 'Tom Lanyon'; 'David Prall'; 'cisco-nsp'
Subject: RE: [c-nsp] Change BGP default-originate to IGP?

So if I understood it correctly you are concerned that the router will start
to originate the default prior to receiving full BGP table from its upstream
right?
The simplest solution would be to place a static default route pointing to
the upstream -so in case of the above happens the router wouldn't blackhole
till it gets the full feed. 
Or you can base the condition of default advertisement on several prefixes
from all around the place instead of just one -but trying to match e.g. 10
prefixes from 400k well...
The problem with this though is that on IOS you can't AND the "match ip
address" statements under the route-map only OR -applies to all the match
statements of the same kind. 
So you could use static routes for the list of desired prefixes each with a
high AD -redistribute them into bgp with specific community and match for
the prefixes+community in "non-exist map". 
So once you'll get all the prefixes from BGP -only after all cease to exist
in the bgp table with the specific community of yours -the router will start
to advertise the default route. 

adam
-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Tom Lanyon
Sent: Thursday, September 27, 2012 4:58 AM
To: David Prall; cisco-nsp
Subject: Re: [c-nsp] Change BGP default-originate to IGP?

Is there a specific order in which BGP updates are sent/exchanged/processed?

The concern I have with tracking upstream routes is that the route tracked
would need to be one of the last routes received (if not the last) to ensure
that the router has full visibility.  This seems quite non-deterministic and
so potentially fraught with 'weirdness'.

Thanks,
Tom

On 27/09/2012, at 12:19 PM, David Prall wrote:
> Why not use selective advertisement of the default based on receiving 
> a specific route from your carrier or an upstream you know to be stable.
> 
> http://www.cisco.com/en/US/docs/ios/12_3/iproute/command/reference/ip2
> _n1g.h
> tml#wp1037042
> 
> David


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