ā02-27-2012 08:07 AM - edited ā03-04-2019 03:27 PM
Hello,
I'm not sure what problem that I'm facing but hoping any expert here could help.
Customer router, CE HQ site is connected to 2 ISP PE router , PE-a and PE-b using OSPF. PE-a act as active link and PE-b act as backup link.
All customer branches sites are using CE HQ as a gateway to internet.
Then, when active link down, all the branches cannot access to internet. Further check, default route cannot be learn from other branch.
When I checked the config at router PE-a, configuration for default-information originate for both OSPF and BGP were in place but NOT in router PE-b.
So while investigate the Active link PE-a (that was down at that time), default-information originate for both OSPF and BGP were added at router PE-b.
After that, customer branches site can access to internet.
When the Active PE-a router up, traffic still goes thru PE-b instead off router PE-a. Config default-information originate at PE-b had to be remove back so that traffic could flow back thru PE-a.
Do you guys have any idea why this happen?
Sample config at PE router
#####Active link (Router PE-a)########
!
router ospf 2627 vrf V739:ABC
log-adjacency-changes
redistribute bgp 24645 subnets
network 114.133.89.212 0.0.0.3 area 0
default-information originate
!
!
router bgp 24645
!
address-family ipv4 vrf V739:ABC
redistribute connected
redistribute static
redistribute ospf 2627 vrf V739:ABC metric 1 match internal external 1 external 2
default-information originate
no auto-summary
no synchronization
exit-address-family
end
#####Backup link Router PE-b####
router ospf 2627 vrf V739:ABC
log-adjacency-changes
redistribute static subnets
redistribute bgp 24645 subnets
network 27.146.93.64 0.0.0.3 area 0
!
!
router bgp 24645
!
address-family ipv4 vrf V739:ABC
redistribute connected
redistribute static
redistribute ospf 2627 vrf V739:ABC match internal external 1 external 2
no auto-summary
no synchronization
exit-address-family
end
Thanks
ā02-27-2012 08:30 AM
At the remote branches, from a distribution switch, were you able to see 2 default routes in OSPF or just one?
Can you verify both routers were injecting the default route into OSPF by issuing the command:
show ip ospf database external 0.0.0.0
(we need to perform this command while having both routers with default-information originate configured)
It is expected to have 2 entries. If you want PE-A to be primary and PE-B to be secondary, you can add the metric-type option on the default-information originate command. Metric-Type 1 for the primary and leave the other as is which will result Metric-Type 2 (default).
ā02-27-2012 08:45 AM
Hello Edison,
Thanks for replying. Very helpful
Btw, is the any reason or where I should start to check when there is only one entry of default route when issuing command show ip ospf database external 0.0.0.0?
ā02-27-2012 11:21 AM
Your remote sites will use the default route learned via OSPF and the command I suggested will verify if both routers are advertising it, which they should.
For OSPF troubleshooting, it is recommended to see the OSPF table then the routing table.
BTW, the default-information originate in BGP should only be apply on the PE routers where the internet is connected, not in the branch routers, that's how it is configured?
In the branch routers, you should only have default-information originate under OSPF.
ā02-28-2012 12:18 AM
Thank you
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide