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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 Network in need of a dynamic routing protocol
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Commented:
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


Don JohnstonInstructor
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Top Expert 2015

Commented:
> 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
amigan_99Network Engineer

Author

Commented:
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?
Instructor
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Top Expert 2015
Commented:
If you want failover AND policy based routing, I would use object tracking with PBR.

http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtpbrtrk.html
amigan_99Network Engineer

Author

Commented:
Great "set ip next-hop verify-availability" - never heard of that.  It sounds like OSPF then would really not be needed in this scenario.
amigan_99Network Engineer

Author

Commented:
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

Don JohnstonInstructor
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Top Expert 2015

Commented:
Try "ip sla"...

At some point (I forget which version) the command went from "rtr..." to "ip sla..."
amigan_99Network Engineer

Author

Commented:
Bingo!  Thanks!

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