routing between core and distribution blocks

[mo shea]

Hi...

We use a collapsed core design where all the 2950 access switches connect to our 6509 IOS core. We need to connect an external building via wireless connectivity to our core switch.

In the external building 4 2950 switches will connect to a 3750-12S (all SFP ports) which in turn connects to the wirelss interface (lightpointe FSO).

I was wondering whether to treat the 3750 as a normal access switch or as a distribution switch, and if the latter is better, what kind of routing protocol is recommended?

Thanks.

[lgijssel]

You will probably only have one wireless link to the 3750? In that case it will not make much difference wheater you use L2 or L3 connection. If there were two links, I would advise you to use L3 connection because this eliminates spanning tree issues.

Just make a connection to a dedicated port on the core switch and you are off!

It seems logical to consider the 3750 as a distribution switch, in fact you have functionally added a new block to your existing topology.

Regards,

Leo

[arvindchari]

IMHO switching (L2) would be a lot faster if you dont need the additional control offered by routing in the form of ACL's

[nethelper]

Hello,

I would agree that a Layer 2 connection is more efficient, unless you have two or more VLAN´s that only exist in the remote building, and that need to communicate with each other. In that case, it would make more sense indeed to let the 3750 do the routing, simply because the hop count, or distance, is less than if you would the 6500 do the routing. Otherwise, I would configure all the layer 3 on the 6500, and also configure that switch as the root for all VLAN´s.

Regards,

Nethelper

[mo shea]

Thanks guys for your valuable feedback.

I just want to confirm a point that Nethelper suggested about the root placement.

Currently we use MST with 2 instances configured for vlans. The 6500 is the root for both instances.

What we plan now is to allocate two vlans from instance two to the remote area, hence making the 6509 as the core. I think this is more like what nethelpr suggested.

I would like also to clear a doubt about the logical configuration if the 3750 would be doing the routing.

Would the steps be?

1. Create VTP domain on the 3750 (different from that on the 6509) and make it a server

2. Create the 2 vlans on the 3750.

3. Run eigrp or static routing on both 6509 and 3750.

4. As for STP, Shall I run a separate MST instance or keep it as that of the 6509?

I would love to know if there is a complete sample configuration of such a situation (core & Dstribution layer example) that I can study.

Thanks a lot

Thanks

[nethelper]

Hello,

you want to totally separate the 3750 switch from the rest of the network and use static routing or EIGRP to connect the 3750 to the rest of your network, is that correct ? If so, create the VTP domain on the 3750, as you said, and the VLAN´s. As for MST, the instance needs to run on the 3750, since the VLAN´s will be totally separated from the 6509. In addition, I would use static routing, that should be sufficient if there is only one uplink between the 3750 and the 6509...

Regards,

Nethelper