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 - jeffhaas@merit.edu