OSPF Path selection

[vinod.pandita]

Following is my setup

RA---- Router A

RB----- Router B

RC----- Router C

RC-512kbpslink--RA--2Mbps ink-RB-128Kbps-RC

RA is connected to RC with 512 kbps link and RA is also connected to RB with 2 Mbps link.Again RB is connected to RC with 128 link.

we are running OSPF

RA--- area 0

RB-----area 10

RC------area 10.

Problem we are facing is that when we make ping to Eth/ serial port of RC from RA location it choses path via RB only.

And if we shut down the link between RB and RC it still choses the same path.

what is the possible reason.

Please suggest the fix.

[minumathur]

Hi.

i think , you need to shut RA to RB ( 2 MB connect), then try.

Minu

[kamlesh.sharma]

hi Vinod,

it is happening bcos link between RA and RB is 2mbps higher than link between Ra and Rc but your second sentence about taking down the link between RB and RC is quit amazing as it should take RA to RC direct link of 512 kbps well for troubleshooting further we need to look at routing table and metrics why it is misbehaving like this.

you need to specify which interfaces are in area 0 and area 10 from these three router's well above what you are publishing and routing table and ospf configuration will gives us the braoder view of the topology.

please rate if it helps.

kamlesh

[vinod.pandita]

Kamlesh

Details are as following

Serial port RA-RB are in area of RA i.e area 0

Serial port RA-RC are in area of RA i.e area 0

Serial port RC-RB are in area of RB i.e area 10

When all likes are up OSPF shows metric from RA to RC via RB as 850 approx.

But OSPF dont calculate metric when link between RB-RC is down despite RA is able to ping RC.

It shows route via RB i.e looped condition.

Means that it is not at all following 512 kbps link.

Suggest solution if any

[devang_etcom]

what are the status of link between RA and RC...

[kamlesh.sharma]

Hi vinod,

Are you using any bandwidth command in interface mode like bandwidth 512.

make sure everywhere you are using bandwidth command and one more thing to add with devang which ip address or network you are trying to ping and if you can put routing table as well to clearly find out the problem as in my opinion everything should work fine and if it is loopback address from RC and published in area 0 or 10 it will be reachable directly ro RC not from RB.

well if there any other link between RB to RC other than this 128 k link than we need to look at it.

please rate if it helps

kamlesh