Hi,
I set up a lab enviroment at home to practice MPLS/VPN. I have dual PE routers (2611) and dual CE routers (2500). These routers form a square topology.
R2 -------- R1
| |
| |
| |
| |
R4 -------- R3
\ /
\ /
10.10.1.0/24
10.10.2.0/24
10.10.3.0/24
10.10.4.0/24
10.10.5.0/24
10.10.6.0/24
I have OSPF + iBGP running between PEs and OSPF only between a PE and a CE. Both CE routers announce 10.10.1.0 - 10.10.6.0/24 subnets to PEs via OSPF. On PE R2, I aggregated these 10.x.x.x subnets into 10.10.0.0/21, but not on R1. The RID for R1 is 1.1.1.1, for R2 is 2.2.2.2, for R3 is 3.3.3.3 and for R4 is 4.4.4.4.
When I pull the link between R2 and R4, I expected OSPF on R2 would detect the link status change and perform SPF calculation. As a result, the OSPF routes in R2's VRF table will be removed and R2 will begin to use the route announced by PE R1 for the 10.10.x.x network.
However, when I looked at the following logs. it seems like BGP(1) process kicked in first and realize all routes disappeared. OSPF didn't react to the link pull until 5 seconds later. Also, R2 withdrawned the route of 3.3.3.3 and 4.4.4.4.
*Mar 1 04:58:07.465: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to down
*Mar 1 04:58:07.597: BGP(1): route 65000:2:172.16.2.0/24 down
*Mar 1 04:58:07.601: BGP(1): route 65000:2:3.3.3.3/32 down
*Mar 1 04:58:07.601: BGP(1): route 65000:2:4.4.4.4/32 down
*Mar 1 04:58:07.605: BGP(1): route 65000:2:10.10.1.0/24 down
*Mar 1 04:58:07.605: BGP(1): route 65000:2:10.10.2.0/24 down
.....................
*Mar 1 04:58:07.613: BGP(1): add request for 65000:2:3.3.3.3/32
*Mar 1 04:58:07.617: BGP(1): Add request installing 3.3.3.3/32 -> 1.1.1.1 to Home IP table
*Mar 1 04:58:07.617: BGP(1): add request for 65000:2:4.4.4.4/32
*Mar 1 04:58:07.617: BGP(1): Add request installing 4.4.4.4/32 -> 1.1.1.1 to Home IP table
*Mar 1 04:58:07.621: BGP(1): add request for 65000:2:10.10.1.0/24
*Mar 1 04:58:07.621: BGP(1): Add request installing 10.10.1.0/24 -> 1.1.1.1 to Home IP table
*Mar 1 04:58:07.625: BGP(1): add request for 65000:2:10.10.2.0/24
....................
*Mar 1 04:58:07.641: BGP(1): nettable_walker 65000:2:172.16.2.0/24 route sourced locally
*Mar 1 04:58:07.641: BGP(1): 1.1.1.1 computing updates, afi 1, neighbor version 136, table version 147, starting at 0.0.0.0
*Mar 1 04:58:07.645: BGP(1): 1.1.1.1 send unreachable 65000:2:3.3.3.3/32
*Mar 1 04:58:07.645: BGP(1): 1.1.1.1 send UPDATE 65000:2:3.3.3.3/32 -- unreachable
*Mar 1 04:58:07.645: BGP(1): 1.1.1.1 send UPDATE 65000:2:4.4.4.4/32 -- unreachable
*Mar 1 04:58:07.649: BGP(1): 1.1.1.1 send UPDATE 65000:2:172.16.0.0/24 -- unreachable
...................
*Mar 1 04:58:12.818: - OSPF db timer at 16 min 47 sec 0 9 -
*Mar 1 04:58:12.970: OSPF: running SPF for area 0.0.0.0
*Mar 1 04:58:12.970: OSPF: Initializing to run spf
*Mar 1 04:58:12.970: OSPF: No new path to 172.16.2.1
*Mar 1 04:58:12.970: It is a router LSA 172.16.2.1. Link Count 0
*Mar 1 04:58:12.970: OSPF: Adding Stub nets
*Mar 1 04:58:12.970: OSPF: Entered old delete routine
*Mar 1 04:58:12.970: OSPF: No ndb for STUB NET old route 10.10.1.0, mask /24, next hop 172.16.2.2
*Mar 1 04:58:12.970: OSPF: No ndb for STUB NET old route 4.4.4.4, mask /32, next hop 172.16.2.2
*Mar 1 04:58:12.974: OSPF: No ndb for STUB NET old route 3.3.3.3, mask /32, next hop 172.16.2.2
*Mar 1 04:58:12.974: OSPF: Delete path to router 172.16.0.1 via 172.16.2.2 spf 13
So my questions are:
1. What is BGP (1)? Why this process detect link failure immediately?
2. Why didn't OSPF run SPF immediately after link pull? Is there built-in delay or timer on Cisco to intentially hold on the SPF run for OSPF inside VRF?
3. Why R2 only withdrawn 3.3.3.3 and 4.4.4.4, but not 10.10.x.x network?
Your help is really appreciated!
SShang
