We are performing major switch upgrades and moving from a collapsed core design to a proper Core, Distribution, Access design. We have a very odd problem where our fiber connections going from the 4510 to an access closet (Avaya ERS 5698) that currently work fine, do not work when patched into the 9300. No link light whatsoever, and the command sh interface te1/1/1 transceiver says -40dB loss (basically no light signal).

We have tried multiple ports on the 9300s, new transceivers and new cables on both ends. We also had a company come in and verify our fiber runs are fine. Are newer switches more sensitive to loss, or has Cisco's algorithm changed in some way? I'm confused as to why one link would work on a 10 year old Cisco 4510 and not a brand new Cisco 9300. When directly connecting the 9300 to the Avaya by patch cable in the closet, the link does indeed come up. We only see this problem when using the patch panel to the armored fiber.... which previously worked.

closed as too broad by Ron Maupin Dec 31 '18 at 21:52

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • What type and brand of tranceiver is it? – user36472 Jul 6 '18 at 16:43
  • 2
    What the the types / sizes / classes of fibers involved? Sounds like someone has fired a MM laser into SM fiber, or v.v. – Ricky Beam Jul 6 '18 at 18:44
  • Can you please give us the reference of previous and new transceivers? Like Ricky said, most chances that you replacer SM opticable by MM or something like that – Golgot Jul 6 '18 at 21:05
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer. – Ron Maupin Dec 25 '18 at 9:01
  1. check the transceivers. if their are the same standard?
  2. be sure to using LX/LR with singlemode fiber and SX/SR with multimode.
  3. the brand of transceivers is supported by 9300?
  4. set port to default. (conf t# default interface g1/1/1)

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