From: Mark H. Degner (mark@xxxxxxxxxx)
Date: Sun Aug 13 2000 - 23:05:29 GMT-3
Eugene,
You bring up some good points, but default routes in BGP can actually be quite
useful. For
instance, if a corporation were to use a 4000 series router as its Internet rou
ter running BGP, it
would not support the memory required for the full Internet BGP tables. In thi
s case, the customer
would usually request the ISPs customer routes, and a default route. Due to th
e proximity of most
upper tier ISPs to regional NAPs, this is often a better solution than running
full routes.
Assuming, of course, the customer is more interested in advertising their prese
nce than being aware
of every route on the Internet. Often, full BGP routes do not optimize routes
enough to make them
worthwhile. This all depends on the implementation, or course. So in cases li
ke this, partial
routes from the ISP suffice. If you connect to two ISPs, it is good to get the
ir customer routes,
so traffic that would normally never leave their network doesn't traverse the o
ther ISPs link.
Default routes on both links then give you the link redundancy you would want.
I guess what I'm
trying to say is, default routes in BGP have their merits, when implemented in
the appropriate
situations.
I hope this makes sense..
Sincerely,
Mark Degner
CCIE #6110 (as of today)
----- Original Message -----
From: "Eugene Nesterenko" <eenest@msn.com>
To: "Harbir Kohli" <harbirk@sympatico.ca>; "'Ccielab" <ccielab@groupstudy.com>
Sent: Sunday, August 13, 2000 7:27 PM
Subject: RE: BGP default network
> Harbir,
>
>
> That's the different story.
>
> IGRP and EIGRP are effectively IGP-class protocols.
> On the contrary - BGP in most cases runs defaultless - i.e the BGP-speaking
> boxes have no defauls - they know where-and-how-to-get-there.
>
> In the typical scenario, BGP is used on the edge of the local/corporate
> network - i.e. at
> the point where it connects to the real world - i.e. Internet.
>
> IN that case trying to inject any kind of default in BGP, and more, to
> EXPORT that knowledge
> can create real disaster in Internet. Of course that's the bad idea.
>
> Can you imagine that your leaf network will say to the whole world that it's
> DEFAULT ROUTE
> FOR ALL AND EVERYTHING IN THIS WOLD, ESPECIALLY FOR ALL THAT HAVE NO
> EXPLICIT
> ROUTES (or just wrong)?
>
> In that case - using anything like "I'm default" in BGP-world has no sence
> at all.
>
> But in IGP-world - that's normal.
> You have small network - you have one (or may be 2) outbound connections to
> the "BIG WORLD"
> In that case you can instruct your IGP-protocol - it can be OSPF, EIGRP,
> RIP - what you actually like -
> to say "here's default route - send all the stuff that you have-no-idea
> where-to-send to this default path"
>
> And it'll work.
>
> Of course in that case you can get some problem with the "sync-no-sync"
> dilemma (with your BGP).
> But that's another question.
>
>
> Regards,
>
> Eugene
>
> -----------------------------------------
> Eugene Nesterenko, CCIE #5283, CCNP+Security, CCDP, MCSE
> Fax/Voicemail: +1 415 7043497
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