I had a customer which have two 3550 in building A and two 3550 in building G. From A to G they are connected with 1000 Base LH/LH. From all those 3550 they have about sixteen 2950 connected with 1000BaseT or 1000Base SX. The hole are spilt in two cluster(Cluster A and Cluster G). After upgrading those clusters from 12.1(9)EA1c to 121-13.EA1a the connecting between A and G with 1000 Base LH/LH become flapping interface between 3550 many times each day. During the troubleshooting i notice that the linklight became orange -green-orange-green and so on. The customer have one multimode fiber so I rent them 2 1000Base SX, so the problem are temporary solved. What shall I do to go back to they own LX/LH with singel mode fiber.
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Flapping Interface 3550 with 1000Base LX/LH
- Thread starter andgu
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I had a problem with a 3550-12G similar to what you are experiencing. We went through a time where the gig ports would go up and down for no real aparent reason. It turns out that Spanning-Tree wasn't configured properly. Make sure that you configure STP and pick where you want the Root to be.
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