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OSPF path selection

Hi All,

 

Please have a look in to the below senario

 

 

R1 and R2 are directly connected with two links and having IP address 10.0.0.0/24 (ETH 0/0) and 20.0.0.0/24 (ETH 0/1).

 

 

R1#sh ip int bri | ex una

Interface                  IP-Address      OK? Method Status                Protocol

Ethernet0/0                10.0.0.1        YES manual up                    up      

Ethernet0/1                20.0.0.1        YES manual up                    up      

 

 

R2#sh ip int bri | ex una

Interface                  IP-Address      OK? Method Status                Protocol

Ethernet0/0                10.0.0.2        YES manual up                    up      

Ethernet0/1                20.0.0.2        YES manual up                    up      

Loopback0                  192.168.1.1     YES manual up                    up  

 

 

I had enabled OSPF in one link with AREA 0 and another with AREA 1

 

 

R1#sh ip ospf int bri

Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C

Et0/0        1     0               10.0.0.1/24        1000  BDR   1/1

Et0/1        1     1               20.0.0.1/24        10    BDR   1/1

 

2#sh ip ospf int bri

Interface    PID   Area            IP Address/Mask    Cost  State Nbrs F/C

Et0/0        1     0               10.0.0.2/24        10    DR    1/1

Et0/1        1     1               20.0.0.2/24        10    DR    1/1

Lo0          1     2               192.168.1.1/24     1     LOOP  0/0

 

additionally i created a loopback in R2 with OSPF Area 2 enabled.I am having that route in the routing table of R1.

 

 

R1#sh ip route ospf

 

Gateway of last resort is not set

 

      192.168.1.0/32 is subnetted, 1 subnets

O IA     192.168.1.1 [110/1001] via 10.0.0.2, 00:15:38, Ethernet0/0

 

It showing  me that the AREA 2 route (192.168.1.1/32) is reachable via AREA 0 interface eventhough the OSPF cost is  higher on that interface.

 

R1#sh run inter eth 0/0

interface Ethernet0/0

 ip address 10.0.0.1 255.255.255.0

 ip ospf 1 area 0

 ip ospf cost 1000

end

 

R1#sh run inter eth 0/1

interface Ethernet0/1

 ip address 20.0.0.1 255.255.255.0

 ip ospf 1 area 1

end

 

 

R1#sh ip ospf database summary 192.168.1.1

 

            OSPF Router with ID (10.0.0.1) (Process ID 1)

 

                Summary Net Link States (Area 0)

 

  Routing Bit Set on this LSA in topology Base with MTID 0

  LS age: 1179

  Options: (No TOS-capability, DC, Upward)

  LS Type: Summary Links(Network)

  Link State ID: 192.168.1.1 (summary Network Number)

  Advertising Router: 10.0.0.2

  LS Seq Number: 80000001

  Checksum: 0x665E

  Length: 28

  Network Mask: /32

        MTID: 0         Metric: 1 

 

 

                Summary Net Link States (Area 1)

 

  LS age: 1061

  Options: (No TOS-capability, DC, Upward)

  LS Type: Summary Links(Network)

  Link State ID: 192.168.1.1 (summary Network Number)

  Advertising Router: 10.0.0.1

  LS Seq Number: 80000002

  Checksum: 0x9E3A

  Length: 28

  Network Mask: /32

        MTID: 0         Metric: 1001 

 

  LS age: 1179

  Options: (No TOS-capability, DC, Upward)

  LS Type: Summary Links(Network)

  Link State ID: 192.168.1.1 (summary Network Number)

  Advertising Router: 10.0.0.2

  LS Seq Number: 80000001

  Checksum: 0x665E

  Length: 28

  Network Mask: /32

        MTID: 0         Metric: 1 

 

 

Why it is not taking the AREA 1 interface even though the cost is higher in AREA0 interface ( I believe we can sent inter-area traffic to non-backbone area because of the capability transit command ).

 

How can I sent  the traffic to a AREA2 from R1 via AREA 1 interface.

 

Please help.

 

Thanks,

Arun Mohan


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