[nsp] ospf default routes and bgp injection

[Mark Tinka]

cisco-nsp-bounces at puck.nether.net wrote:
> Nick,
> 
> I think it really depends on what you want to achieve and wich IGP
> you're using. As general arguments: 
> 
> 1) customer routes in IGP don't scale. While OSPF/ISIS on modern
> platforms (RISC CPU's) works just fine with 5000+ routes in your IGP,
> scaling to 10000 and above might be a challenge  

As Nick mentioned, using OSPF to carry your infrastructure networks
(Loopback interface IP's mostly) and using iBGP to carry your internal and
customer prefixes is quite a scalable approach.

Nick (sorry to post this in Oliver's thread), you're right. I don't think I
have seen a supporting document anywhere yet (there could be, though), but
this is something that has been presented and agreed on multiple operators
forums and seminars that I've been a part of. 

It scales quite well and offers more features in terms of filtering,
flexibility and all. Just FYI, this is how I run my backbone.

> 
> 2) The more routes you carry in your IGP, the longer PRC takes
> installing the routes in your RIB. This will be in issue if you want
> to tune your IGP for faster (i.e. sub-second) convergence  
> 
> I think one can find addtl. arguments if your specific network and
> routing topology is taken into account. 
> 
> 	oli
> 
> ----Original Message----
> From: cisco-nsp-bounces at puck.nether.net
> [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Nick Kraal
> Sent: Dienstag, 6. April 2004 14:45 To: cisco-nsp at puck.nether.net
> Subject: Re: [nsp] ospf default routes and bgp injection 
> 
>> Following up on this one. We all know that the IGP of choice used
>> should carry only infrastructure networks and kept as small as
>> possible. The rest should be announced via iBGP. Is there a document
>> that explains this rationale clear --having some difficulty
>> convincing some folks. 
>> 
>> Thanks in advance,
>> 
>> -nick/
>> 
>> ----- Original Message -----
>> From: "Gert Doering" <gert at greenie.muc.de>
>> To: "Christopher J. Wolff" <chris at bblabs.com>
>> Cc: <cisco-nsp at puck.nether.net>
>> Sent: Thursday, April 01, 2004 5:49 AM
>> Subject: Re: [nsp] ospf default routes and bgp injection
>> 
>> 
>>> Hi,
>>> 
>>> On Wed, Mar 31, 2004 at 09:58:12AM -0700, Christopher J. Wolff
>>> wrote:
>>>> I've considered ibgp as an end-to-end solution however never went
>>>> so far as to implement it.
>>> 
>>> Completely overkill in this network.  If there's no BGP speaker
>>> "down the road", there is not much use in having all those routers
>>> actually carry BGP information.
>>> 
>>>> My concern is making sure that the entire routing table isn't
>>>> propagated all the way to the edge device, which could be
>>>> something minimal like a 2611XM.  Any thoughts?  Thank you for
>>>> your advice.
>>> 
>>> Have the BGP speakers distribute an OSPF (or EIGRP, or even RIP :) )
>>> default route to the smaller boxes.
>>> 
>>> gert
>>> --
>>> USENET is *not* the non-clickable part of WWW!
>>> 
>> //www.muc.de/~gert/
>>> Gert Doering - Munich, Germany gert at greenie.muc.de
>>> fax: +49-89-35655025
>> gert at net.informatik.tu-muenchen.de
>>> _______________________________________________
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>>> 
>> 
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Regards,

Mark Tinka
Technical Manager, Africa Online Swaziland