North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Community NO-EXPORT
On Wed, Aug 23, 2000 at 09:55:59AM -0700, Bradley Dunn wrote: > On Wed, Aug 23, 2000 at 10:03:21AM -0400, Kai Schlichting wrote: > > Correct me if I'm wrong, but isn't there a synchronization issue here > > as well? E.g.: AS2 is transit provider, probably has bgp synchronization > > on (default), and will only propagate routes to other AS's that have > > made it into their IGP. The question then is: have all 3 routes made > > it into AS2's IGP successfully? Only if the answer is yes, will it > > actually propagate that /16. > > Synchronization is almost universally disabled in the real world. Color me confused, but isn't the synchronization waiting on the NEXT_HOPs showing up in your IGP, not the actual BGP route? After all, the issue is this: BR-A - (your internal network) - BR-B A route shows up at BR-A with a nexthop of some interface on BR-A (or the loopback interface of BR-A). It is then propogated via iBGP to BR-B. It is only unsafe to install said route and propogate it BR-B's peers if the route's nexthop is not reachable by BR-B. This is a far cry from having to inject your BGP into your IGP. I will note that this isn't how Cisco has it documented, and I don't know how they actually treat the sync issue. The documentation actually says it does wait for the route to show up in the IGP. > None of the IGPs in use today would cope well with a full BGP > table redistributed into them. Redistribution of BGP->IGP is > rarely needed or advisable. However, its a wonderful way to see the failure states of your router's IGPs. :-) -- Jeffrey Haas - Merit RSng project - [email protected]
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