From: Sergey (public@svlp.net)
Date: Wed Jul 11 2007 - 06:01:05 ART
I my lab I've got next topology
R1-----R4-----R2
R1 & R2 both announce E2 route 67.0.0.0/24, but R1 use PPP multilink to R4 and R2 use HDLC serial interface to R4
OSPF Network Design Solutions says about E2
"E2 routesE2 routes are the default external routes for OSPF. They do not add the
internal OSPF metrics; they use the remote AS only, regardless of where they are in
the AS. For example, if a packet is destined for another AS, E2 routes add only the
metrics from the destination AS associated with reaching the destination."
So I expect to see in routing table both routes (one from R1, another from R2), in real life I see only
67.0.0.0/24 is subnetted, 1 subnets
O E2 67.0.0.0 [110/20] via 192.168.100.1, 00:00:15, Multilink10
if I shutdown int Multilink10 another route appear in routing table with the same metric
67.0.0.0/24 is subnetted, 1 subnets
O E2 67.0.0.0 [110/20] via 192.168.200.1, 00:00:15, Serial1/1
after some investigation I've found that ASBR has different cost
R4#sh ip ospf border-routers
i 192.168.200.1 [64] via 192.168.200.1, Serial1/1, ASBR, Area 10, SPF 48
i 192.168.10.100 [1] via 192.168.100.1, Multilink10, ASBR, Area 10, SPF 48
I've changed ospf cost on serial interface so
R4#sh ip ospf border-routers
i 192.168.200.1 [1] via 192.168.200.1, Serial1/1, ASBR, Area 10, SPF 52
i 192.168.10.100 [1] via 192.168.100.1, Multilink10, ASBR, Area 10, SPF 52
And only after I've changed ospf cost both routes appear in routing table
67.0.0.0/24 is subnetted, 1 subnets
O E2 67.0.0.0 [110/20] via 192.168.200.1, 00:00:15, Serial1/1
[110/20] via 192.168.100.1, 00:00:15, Multilink10
My question is, why cisco take in account cost to ASBR for E2 routes?
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:40 ART