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InterArea OSPF Routes On NE40E are misssing becasue of bad OSPF Multi Area Design

Publication Date:  2012-07-27 Views:  42 Downloads:  0
Issue Description
The customer network is Mobile operator which provides interconnection between diferent city via IPBB which contiains PEs and Ps and also it delivers internet services via DCN and we have Gi Routers to connect between IPBB and DCN
All the routers are NE40E with V600R001C00SPC800
The IP BB is running MPLS VPN to carry routes of different services
Gi is considered like a customer for PE ,OSPF is running between PE and GI
Static routes is existing between GI and Firewalls
Internet traffic from other sites Passes via IPBB PEs then GI then FW then BR then Internet
The issue happens when we change the static routes between Gi and FWs to OSPF with area 0


Alarm Information
Null

Handling Process
1-check the type three routes that comes from other sites on PE and we found it is existing in the vpn routing table
display ip routing-table vpn-instance Gi_VRF
2-Check the same routes on the GI routing table, we didnt find these routes
diplay ip routing table
3-When we display LSDB of the ospf we found that we got the LSA for these routes but it is not installed in the routing table
dispaly ospf LSDB
4-When we change the ospf area between  FW and GI from Area 0 to Area 901,the problem is solved and we got the missing routes, since right now we have ospf are901 are running between PE and GI ,GI and FW
dispaly ip routing table

Root Cause
1-The routes from other sites are advertised to the PEs via MBGP then it is advertised to GI via ospf
2-Gi is running ospf area 901 to PE and ospf area 0 to FW,
3-Gi is considered as ABR connected to area 0.
4-Gi as ABR will reject and discard all the Interarea routes (type 3 routes) that comes from any area except area 0
So Gi will discard the type 3 routes that comes from PE ,since are 901 is runnning between GI and PE.

Suggestions
1-We should take care when we run ospf multia area as the CE-PE routing protocol,Area 0 must be direrctly connected to PE.

END