General discussion


Network Design Help - Spanning Tree

By scrobins ·
I am working on a network design for one of my company's newly aquired buildings. I am trying to implement a network design that keeps spanning tree to a minimum but offers uplink redundany. We were approved and have recieved the following equipment for the new site.
2 Cisco 6509 switches running IOS
1 24 Gigabit fiber SFP blade in each
1 supervisor 720 blade in each.

12 Cisco 3750 48 port POE, with 2 Gig SFP's
2 3750's per wiring closet. Configured with two vlans per stack one for data and one for VOIP.

Initial config i came up with is running one port of each 3750 to the first 6509 and the second port to the other 6509. Running a 3 member 1 Gigabit Portchannel between the two 6509's and VRRP running for each VLAN alternating between the two 6509's for a more load balanced design.

My questions are:
1. Is this a good design, are thier improvements that could be made?
2. What if any spanning tree would be needed?

I have additional network information if needed, i did not include do to space limitations, including a visio diagram and a intial ios config of one of the 6509's.
Please email any questions to

This conversation is currently closed to new comments.

Thread display: Collapse - | Expand +

All Comments

Collapse -

by MJT In reply to Network Design Help - Spa ...

You don't mention how you are doing the layer 3 setup. As long as you use a different VLAN for each 3750 plugged into one 6509, then you do not have to run spanning tree.

The links to the 6509 from the 3750s are layer 2 links. The link between the 6509s are layer 3. The VLANs extend only from the 3750 and terminate in the 6509, and they are not duplicated in other wiring closets. Connectivity between the closets are accomlished using layer 3 links.

At layer 3, redundancy is provided through a redundant gateway protocol, such as HSRP, which allows one 6509 at a time to own the gateway. From what I know of VRRP, it acts the same way, so how would you load balance between the 6509s. Could you elaborate on how you would load balance?

You have come up with a good design so far since this is essentially Cisco's ollapsed Core Switch Block Design.

I have set up one of these configs myself using 6509s with Sup720s and 3550s. However, mine was a little more strange and complicated since the powers-that-be threw in redundant links between the wiring closets. But, it is in production and it works. You won't have to worry about that because you are describing a standard config.

I would configure spanning tree anyway, just in case but you wouldn't be using it.

You should also look at turning on spanning-tree bpduguard on all the ports, just to keep people from plugging switches in on you.

If you could furnish some additional info, I would be glad to help.

Related Discussions

Related Forums