2 x 3750G-12S core switch configuration

Unanswered Question
Jul 29th, 2008

Hi

I have recently been asked to replace 2 x 4908 core switches and replace them with 2 x 3750G-12S fibre switches as the new cores. The requirement was to configure the new switches the same as the old 4908's but unfortunately the config will not work on the 3750g switches. The 4908's used not 5 Vlans (1,10,20,30,999), Bridge IRB, Bridge-groups, subinterfaces and BVI interfaces. Im now in the situation where I have not configured core switches before and would appreciate any help possible with the configs. All 12 ports are gig SFP fibre ports.

The manager has now decided he is happy to reconfigure the entire network from a blank canvas and I now have the job of configuring the network from the core up, which for a CCNA is quite a job!

Please can someone advise me on the best configuration for the core using the 2 x 3750G-12S switches.

Many thanks

Mark

I have this problem too.
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lee.reade Tue, 07/29/2008 - 05:34

Hi,

Well it really depends on the size of your network, do you have a large distribution block aswell?

Or do you have a collapsed core/distribution, where your access switches will plug directly into your new core switches?

Let us know.

HTH

LR

bavingtonm Tue, 07/29/2008 - 05:46

I believe it is a collapsed core/distribution as all switches are link via fibre.

I have attached the original network diagram.

Thank you for your time.

Mark

lee.reade Tue, 07/29/2008 - 05:58

Hi,

Well what you want to do is determine, from the old 4500 configs, which switch was the stp root for each vlan, and then configure your new core like for like.

As best practice you will want to have core 1 as stp root for half the vlans, and core 2 for the other half. Also do the same for hsrp, if you use it, so that the stp root for a certain vlan is also the hsrp primary for that vlan.

You will need to configure the layer 2 trunk between the two new core switches, since all your uplinks from the edge switches are 1gig, you might consider channeling 2 or 3 gig links between the two new cores into one fat layer 2 pipe, this will improve performance and available bandwidth etc.

Have fun!

HTH

LR

bavingtonm Tue, 07/29/2008 - 06:15

Hi

Thanks for the advise!

Is it possible for you to point me in the direction of a sample configuration of what I'm trying to achieve? This will be really useful for me to see how it should look.

Many thanks

Mark

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