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Occasional Advisor


We’re expanding our network into multiple sites. For simplicity, site A has a AD, DNS, DHCP, 5300 and several port based VLANs. Site A will be connected to site B with a 10Mbit MetroE link. Site B will have AD, DNS, DHCP, and a 3400. We expect more sites to be added in the near future.

MetroE functions at layer 2. We were planning on using RIP or OSPF between site A’s 5300 and site B’s 3400. Site A has about 200 computers with about 25 VLANs. Site B has about 20 computers with 5 VLANs.

I have several questions:

1. Is it optimal to use VLANs across the MetroE, or to just turn on RIP or OSPF?
2. Should we use RIP of OSPF? OSPF seems a bit more complex to configure at first glance.
3. We’d like site B to use site A’s Internet connection via MetroE because of content filtering, etc. We’d like site B to start using its DSL connection in the event site A’s Internet connection drops or MetroE fails. How could this be done?

Thanks for your help!
Frequent Advisor

Re: RIP or OSPF?

1. I always recommend a routing protocol over WAN links. I've had to support un-routed WANs in the past; I'll never do it again.

2) RIP version 2 should be fine for what you describe.

3) Site A should advertise a default route to Site B. That will support the normal environment. To support failover to the DSL connection, there are normally two approaches:

#1) A static default route with a high administrative distance. This can work even if the DSL connection cannot advertise routes. Unfortunately, it doesn't look like this is supported by by the 3400.

#2) Have the DSL router advertise an default route to the 3400. You will need change the cost of the route learned from the DSL router so that the route learned from Site A is "better" than the route learned from DSL. This requires that whatever terminates the DSL connection can advertise via RIP.

Hope this helps,