Configuring Redundant Fiber Connections

Unanswered Question


I need to built a more redundant cisco 3550 telecom closet connectivity that we currently have.

At the moment, each cisco 3550 has its own fiber run back to our main telecom closet where the switches connect to a 6509 router.

However, when either a fiber goes down or a switch fiber module uplink goes down, it take an entire floor down.

What suggestions can you provide to make it more redundant?


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simontibbitts Thu, 09/10/2009 - 07:16
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So currently you just have one fiber connection from the 3550s to the 6509?

If you just have one then the only solution is to add another fiber link for redundancy. If you only have one 6509 then your best option would be to use an etherchannel to bundle the two links together.

If you have two 6509s to connect to then you can have one fiber to one 6509 and another to the other 6509. For redundancy spanning-tree will block one link and you could load balance by changing your spanning-tree settings so one vlan is preferred over one link and another vlan is preferred over the other link.

An alternative to fudging spanning-tree would be routing at the access layer which is a very good solution:


Leo Laohoo Thu, 09/10/2009 - 15:34
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I worked for an company once and we were only allowed to use one fibre to the floor and cater for redundancy. So we had cablers put copper lines from the floors (17 floors) to the core switch and run copper that way. We made sure spanning-tree use the fibre than the copper was blocked.

To make things alot confusing for spanning-tree, we were using WS-C3500XL switches and Gigastacking GBIC. This means that if spanning-tree chose to use the copper in preference, we configured higher STP cost on the copper ports.

Hope this helps.


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