From: hcb@gettcomm.com
Date: Sat Dec 13 2003 - 19:42:02 GMT-3
Quoting George Yiannibas <hintgy@hotmail.com>:
> OK I admit I have not worked with BGP outside the Lab so here goes:
Let me make a few suggestions/comments about working with real world BGP and
real world service providers.
> After setting up the BGP peering session from my customer's router to the
> ISP border router and receiving the full Internet routing table I noticed
> that the C class network
BING! Forget the terms class A, B and C when dealing with real BGP. The
Internet is classless. Indeed, I've seen again and again, in network operator
forums, a great deal of suspicion of providers that just advertise /24's.
Reality isn't that neat, just as all tax deductions aren't round numbers.
>I was trying to advertise to the outside world did
> not appear on the ISP side. I double checked my configs and I made sure that
>
> the ^$ regular expression in the route-map I was using to prevent the
> transit domain issue (this network will be dual-homed in the near future)
> was correct I started to wonder what went wrong. Then the ISP guy told me :
> do you a have a static route to Null 0 ? Everything become suddenly clear to
>
> me and I remembered BGP theory I had studied for the Lab: you cannot ever
> advertise (even with sync turned off)
Again in the real world, forget about sync. It's a completely obsolete feature
that ISTR Cisco has finally made non-default, and may be taken out of the lab.
>a network under BGP which does not
> appear in your routers' routing table. The C class network was not there so
> it didnt appear in BGP as well. After I put in a static route to null 0 with
>
> an administrative distance of 254 everything worked !
Do you see WHY this requirement is there? There is a very fundamental reason
for it, other than "that's the Cisco way."
> Yes I know we are not supposed to use these static routes int the Lab but
> here I was in the Real World so I could do anything I liked to make my
> scenario work (Huge grin).
>
Some of the lab requirements, to put it gently, are insane. There's nothing
wrong with a properly used static or default routes, and, frankly, I'd want to
think that at least some scenarios only can be solved with them.
> George
>
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