From: san (san.study@gmail.com)
Date: Thu May 19 2005 - 17:26:46 GMT-3
Bob,
Thanks Bob.
Can you check if i am correct.
This problem happens if sync is enabled & Rtr is redistributing BGP to
ospf & that Rtr is not a ASBR
route-maps does not have a "set router-id" option..how can i change
the router-id of adversiting routes ?
Do you have a link to this solution?
/SAN
On 5/19/05, Bob Sinclair <bsinclair@netmasterclass.net> wrote:
>
> San,
>
>
> RFC 1745 says that when synchronization is enabled and you are
> redistributing BGP into OSPF, then the BGP source must also be OSPF ASBR.
> If they differ, BGP considers the route un-synchronized.
>
> The basic problem can be satisfied by making sure that the redistribution is
> done on the BGP border router, and by assuring that the OSPF RID on that
> router is the same as the BGP RID on that router. (which they would be by
> default).
>
> The document you reference points out that it is very difficult, if not
> impossible, to satisfy the RFC 1745 requirement when you use
> route-reflectors. This is because the route-reflector changes the BGP
> source to the RID of the route-reflector. If the RR is not the ASBR, you
> have problems.
>
> As a hack, you can tweak the RIDs so that the OSPF ASBR RID is the same as
> the RR RID, even if they are different routers.
>
> HTH,
>
>
> Bob Sinclair
> CCIE #10427, CCSI 30427, CISSP
> www.netmasterclass.net
>
>
> ----- Original Message -----
> From: san
> To: Cisco certification
> Sent: Thursday, May 19, 2005 12:37 PM
> Subject: BGP basic router-id understanding
>
> Hello Group,
>
> I am trying to understand BGP Notes from 911networks.com. I did not
> understand the below points or how to do it . If possible, can you
> explain me how to solve it ?
>
>
> Statement 1:
> ---------------
> The ospf router-id must be the same as the bgp router-id for
> redistributing the routes from ospf to bgp. It needs to be done
> manually if a route-reflector is involved or it won't work.
>
> Question 1:
> ----------------
> ex: R1---------R2 (RR)------R3
> Should i change the router-id of incoming ospf updates on R3 ? or
> should i change Bgp router-id on R3 ? Any examples.
>
> Closest i found from searching is below, but could not benefit.
> http://www.groupstudy.com/form/read.php?f=7&i=30353&t=30126
>
>
> Statement 2:
> --------------
> The BGP Router-id is used with the synchronization and in iBGP the BGP
> Router-id is used as tie breaker for the BGP path selection
>
> * Just because the next hop is pingable, it does not mean it's a
> valid next hop.
> * Next hop addresses that are reachable only via a default route
> aren't valid.
> * Next hop addresses that are reachable only via another BGP route
> are also not valid.
> Question 2:
> ---------------
> I thought, if there is a problem with nexthop, route will not be
> available in BGP routing table right ?
>
>
>
> /SAN
>
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