Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

I need advice on ring network with Catalyst switches

A local consultant is proposing us the following network solution, and I want it to be validated by experts (I mean you...)

We will have four fiber (1Gb/s) rings:



on which there will be 5 Catalyst 2950 switches each (this is an industrial application, and all the 2950's will be connected to always-on devices - not offices - with very low broadcast traffic). The rings will be connected via three Catalyst 3550 switches (where edges connect) and a fourth (edge) Catalyst 4507, through which we go to the data centre. They are proposing four VLan's and Rapid Spanning Tree as main recovery protocol. I believe RST (or spanning tree, for that matter) will not work very well on rings, and will force heavy traffic across the 2950's (up to 300 Megabits/sec) nearest to the 4507, mainly when the RST has blocked ring sides. What do you say?

Thanks a lot & Best Regards

New Member

Re: I need advice on ring network with Catalyst switches

Need more info.

1. Are the rings being proposed due to distance and fiber constraints? Such as a metropolitan network or is your environment a large campus?

2. Is it just data? or data and voice?

New Member

Re: I need advice on ring network with Catalyst switches

Thanks for your reply.

This installation is a 35-mile long (8-lane) highway. The data center is about 8 miles from the south endpoint. The purpose of the network is fully automatic toll based on vehicle electronic tags.

There are two rings to the north and two to the south from the data center. These are NOT concentric rings. They touch each other via the Catalyst 3550's: two to the north, one to the south, and via the 4507 at the data center:




4=4507,3=3550, O=rings with 5 or 6 2950's each.

All traffic flows towards the 4507 and throuhg it, to the data center.

We believe the spanning tree will block one side of each ring, limiting capacity, and worse, all data traffic will pass thru the smaller Catalyst 2950's closest to the (4507) data center, overloading them. The larger 3550's are used as broadcast blockers (between rings), and are not physically or topologically close to the 4507. We also believe that, as this is an always-on installation, broadcast traffic should be minimal (after initial power-on settling).

Fiber is monomode, and the underlying protocol is Gigabit Ethernet.

Voice traffic should be minimal, as we will have just ~25 IP Phones along the network (one on each toll portal, plus 3 or 4 at the data center)

Traffic is quite heavy as there are between two and four pictures (200 Kbytes each) taken of every vehicle passing a toll portal (21 portals in all). Around 300 Mbits/sec worst case.

Thanks again & Best Regards


CreatePlease login to create content