Changing OSPF Network Type

[kmckaypason]

Hi everyone,

We have a few sites all interconnected through VPLS and are coming around to realizing our current OSPF network type is not the best choice. Because it is an Ethernet handoff, the default OSPF network type is Broadcast which in this case, has proven to be troublesome.

We have run into a few scenarios where connectivity between individual sites has been severed due to some provider misconfiguration or issue and OSPF did absolutely nothing. I have done some labbing and have confirmed that moving to an OSPF network type of Point to Multipoint Broadcast will resolve any issues related to this type of outage in the future.

My question is.. what would be the most efficient way of moving to a new network type in that OSPF area? If I change the OSPF network type on one device from Broadcast to Point to Multipoint Broadcast, that device will no longer be able to peer with the rest of devices on that network as you cannot mix OSPF network types of broadcast and point to multipoint from my understanding. Is there any way of doing this without breaking connectivity all at once? If I could somehow configure the network types all at the exact same time, I guess It would be a minimal outage but I am wondering if there is a better way!

Thanks!

[Muhammad Thanveer]

Hello,

I never thought of this but after your question I started thinking of it.

How will it be to create GRE tunnel and run ospf on it then migrate on the real interface?

BR

Thanveer

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[kmckaypason]

Hi Thanveer,

Thank you for your response. Unfortunately not all of these devices support GRE tunnels so this will not be an option for us.

I was thinking maybe configuring an additional VLAN over the VPLS WAN and establish routing adjacencies with all of the devices. In this way, I could begin migrating the OSPF network type over the VLAN we are currently using while the new one I've created would still function. Bit of up front work, but I am thinking it should probably work.

[Bilal Nawaz]

Hello, This will work - but your strategy seems a bit long with all respect (after all you came up with a perfectly good solution!)

Maybe you must stick to IP addresses on your VPLS network etc...

however, instead of creating the new interim solution and then changing the old OSPF network types, then deleting your transition solution, why not just create the new one with the correct config and then take all the unwanted config off (old interfaces/VLAN). This way you have to do it once, not twice. But as I mentioned before, perhaps you're under limitation of specific IP's that you use in your WAN. Anyhow, just thought it would save you time and little trouble :)

hth.

[Muhammad Thanveer]

Just thinking of an other solution if it works for you, Why cant we go with static routes, if the sites are few and then migrate network type, then delete the static routes.

Br

Thanveer

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