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Home > Archive > CCNP > August 2000 > Internal BGP Question.
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Internal BGP Question.
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| Quick question about BGP...
Now if a Router A is running BGP and talking to Router B running BGP (both routers in same AS, therefore Internal BGP) will Router B learn of the A's directly connected networks via Internal BGP? Or are these networks (being in the same AS) disregarded by Router B?
Or must B learn of A's directly connected networks via another routing protocol (ie. EIGRP)?
Not sure if I am clear on that or not... if not, let me know and I will try and rephrase it.
Thanks guys.
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| Peer connection between two routers can be established within the AS (IBGP)or different *** (EBGP).
It is essential to have IP connectivity between the two neighbors for the transport sesson to take place. IP connectivity has to be achieved via via a protocol different from BGP; otherwise, the sesson will be in a race condition.
An example of a race condition follows: neighbors can reach one another via some IGP, the BGP sesson gets established, and the BGP updates get exchanged. The IGP connection goes away for some reason, but still the BGP TCP session is up because neighbors can still reach each other via BGP. Eventually the session will go down because the BGP session nanot depend on BGP itself for neighbor reachability.
An IGP or static route can be configured to achieve IP connectivity.
The above information is from cisco press book Internet Routing Architectures by Bassam page 126 and 127.
Regards,
Ravi | |
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| You lost me at "the IGP session goes away for some reason". I don't understand why the IGP session would go away. I thought that once the BGP route was injected into IGP the BGP session ended because IGP now has a route to its neighbor AS. Or are you saying that the "race condition" is a result of some error causing the IGP session to go away, and leaving BGP session active? Please help...I am wanting to learn BGP inside and out. Thanks.
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LANlord :-)
MCNE,MCSE,CCNA | |
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Good luck on the "learning BGP inside and out" trick . . . let me know when you do.
Anyway, The IGP may go away for any number of reasons, he's just saying that when it does, your BGP session will continue any current conversations it's engaged in. However, once it stops, it will not start back up again until it has some sort IGP connection (i.e. static route, EIGRP, etc). | |
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| BlueBaron,
I'll try to keep you posted on my BGP progress. Maybe someday I'll be able to answer one of your questions.
Thanks for the clarification on that. I am going to take the BCSN 2.0 test soon and I figure I might need to know some of this stuff. Thanks again. |
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