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amigan_99Flag for United States of America

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OSPF configuration and route preference

I want to create a very simple OSPF network with two links between two devices.  All data to PCs should go over link A unless there is failure in which case data to PCs would go over link B.  All data to IP phones should go over link B unless there is a failure in which case data to IP phones would go over link A.

I believe the config below would start route exchange between the two devices.  But the traffic would here be load balanced as the two links would have the same cost.  How to go about implementing the preferences I described above?  Thank you.

Router A:
router ospf 87
router-id 10.10.69.1
network 10.10.100.0.0 0.0.0.255 area 0

Reouter B:
router ospf 87
router-id 10.10.69.2
network 10.10.20.0 0.0.0.255 area 0
network 10.10.21.0 0.0.0.255 area 0 User generated image
Avatar of Klinkeye
Klinkeye

Actually 10.10.7.4 is the network address. Your 3750B router on Link B should be 10.10.7.6

On the interfaces for Link B you would:
ip ospf cost <value>

As per: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080094e9e.shtml#t6


Avatar of Don Johnston
> How to go about implementing the preferences I described above?

Policy Based Routing (PBR).

http://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html
Avatar of amigan_99

ASKER

Using ip ospf cost <value> on the interfaces would send send all traffic one way or the other.  Not sure that helps me send the different traffic types to different interfaces.

Using PBR with set ip next-hop would definitely send the traffic to the correct interfaces.  But it's not clear how this would help with the redundancy.  e..g if link A fails I want traffic to the user data subnet to use link B.  Are you saying that under regular conditions the PBR next-hop would take priority (administrative distance 0 as with a static route)?  And then in the event of failure the remaining OSPF-learned route (AD 110) over link B would take over?
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Avatar of Don Johnston
Don Johnston
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Great "set ip next-hop verify-availability" - never heard of that.  It sounds like OSPF then would really not be needed in this scenario.
Alas - it looks like rtr command is not available on the 3750 w 12.2(46)SE

spare-c3750-1(config)#rtr ?
% Unrecognized command
spare-c3750-1(config)#rtr

Try "ip sla"...

At some point (I forget which version) the command went from "rtr..." to "ip sla..."
Bingo!  Thanks!