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Migrating from Tokenring to ethernet without changing address


I have some tokenrings with very critical servers. During history a lot of accessing clients have been configured with the ip-addresses of those servers instead of the domain name of the servers. In other words the servers are not only accessed via DNS resolving.

I would like to move those servers to ethernet but without changing their ip-address. I cannot move them all overnight. I need to have their subnet on both their tokenrings and some new ethernets during the migration period.

There must be lots of fellas out there that has done this kind of migration.

I am looking for experiences.

The servers are accessed via IP. They are not communicating among themselves.

I could imagine different scenarios.

1) Establishing small translational bridging devices without ip routing enabled between the tokenring and the ethernet.

2) Same but using DLSw+

3) Using NAT to mascerade the true address og the servers and still let the clients access the same ip-addresses

4) duplicate subnets and controlling the traffic using host-routes.

Some of these methods are hard to implement and still maintain a redundant setup.

Anyone have tried any of these with good or bad experience ?

Thanks Christian

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Re: Migrating from Tokenring to ethernet without changing addres

We did a similar migration, moving servers from ARCNet to Ethernet. We just put Ethernet cards in the ARCNet servers and hooked them up to the Ethernet switches. They were running both ARCNet and Ethernet at the same time. When the server receives a request, it will send the reply out the same interface it came in. You don't have to mess with any IP address changes because it is a layer 3 protocol. IP runs independent of the lower layers. If this is an option, I think it's probably the easiest.

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Re: Migrating from Tokenring to ethernet without changing addres


We did same migration by adding second NIC and assigning new subnet. However this was Window NT environment hence we used two WINS servers that replicate their database so that users on the new subnet can access legacy apps. The new subnet has its WINS as primary and old WINS secondary. In this way legacy devices will to continue to connect via the old network and migrated devices over the Ethernet network.

If your servers are WIN NT make sure you set correct WINS/TCP binding order .

All the routing was done on the 6509 L3 switches, which was connected to legacy network via external router over ospf protocol.

I think this is easiest way !!!!

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