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dsterling

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OSPF cost on vlan to favor a new vlan used for OSPF.

OSPF cost on vlan to favor a new vlan used for OSPF.

I’m working on a network that has vlan 15 used for OSPF routing from our Data Center switches to our Core Switches, the vlan being used for OSPF (vlan 15) needs to change to a new vlan (vlan 178). I’m thinking I could create a new vlan 178 and place it into ospf to form neighbors relationships and adjust the cost on the old vlan 15 to prefer vlan 178 for OSPF and once the routing is confirmed that OSPF routes prefer vlan 178 then OSPF will be taken off of vlan 15. What I’m wanting to do is transfer the interfaces in OSPF to  gradually move over to vlan 187, in this way one interface could be transferred at a time, this would make it a slow process, but this would be a preferred method over doing all OSPF interface to the new vlan 178.

I’m not sure how I could do this, I was thinking of using a route-map with an access-list, but I don’t think an access-list can filter traffic on the local device.

I would like a suggestion or two as to what can be done to accomplish this?
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mikebernhardt
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It really shouldn't be a big deal. As you already suggested yourself, add the new vlan 178 on both sides of a particular link, make sure you see a neighbor relationship on that vlan. Look at "show IP route" and you should see 2 routes to the destination.

Then add a high ospf cost to vlan 15 on both sides. For the additional connections where only vlan 15 exists, it won't change anything. Where 178 exists, it will quietly move from 2 equal routes to a single route on vlan 178. Once you're all done you can remove vlan 15 everywhere, or just remove it from the ospf configuration.
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mikebernhardt
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dsterling

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mikebernhardt - that is the idea I was thinking of implementing, but I would like to keep all interfaces in OSPF using vlan 15 independently moved to from using vlan 15 to using the new vlan 178 for OSPF, one interface at a time, in this way it could be a controlled transfer of interfaces over to the new vlan 178? Do you know if this can be done?

Thank you,
Dave
Great!!