From: George Yiannibas (hintgy@hotmail.com)
Date: Sat Dec 13 2003 - 20:23:48 GMT-3
Comments inline
> > 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.
You are right but my customers' network IS a C class network that they want
to advertise to the outside world so that's what I did (I read about the
importance of supernetting from NANOG list a while back so I guess I am not
totally clueless)
> >
> > 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.
Again you are right just mentioning theory to help clarify things for myself
and others.
> >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 if you were allowed to advertise a route that is not in your routers'
routing table, it would be so much easier to create havoc on the Internet
and black hole traffic by mistake.
> > 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
Things you would do in Real Life will make you fail the Lab, things you
would do in the Lab will get you fired in Real Life
George
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