I am doing some physical changes to a dev network. The physical hardware is a Cisco ASR9006 to a traffic generator with duplex MM fiber. I am changing from a 10G traffic generator to a 1G. I am stumped and have not been able to get it to work (down/down from "show int tengig ", rx error on the traffic generator).

What I have done in chronological order:

  • Changed the C9k SFP from 10G to 1G. The 1G SFPs are NOT Cisco branded.
  • Changed the bandwidth in the running config from 10G to 1G. Committed the changes.
  • Verified 1G SFPs are in the traffic generator
  • Did a loopback test on the used interfaces of the traffic generator. It worked fine.
  • Lunch
  • Go back to 10G SFPs on the C9k and put a pair in the traffic generator. Left the speed at 1G in the C9k running config. No dice.
  • Went back to the original 10G setup. Worked just fine.

I am lost. Is there anything that I missed here?


Additional information.

Avago 850nm SFP (C9k and traffic generator) Multimode fiber (OM3 50/125), 50micron

  • You need to edit your question to include the standards for the SFPs and fiber used. There are multiple 1G fiber standards, and the SFPs on each end must match and be compatible with the fiber.
    – Ron Maupin
    Oct 23, 2015 at 18:11
  • Will do. Standby.
    – khop
    Oct 23, 2015 at 18:28
  • 2
    It is a distinct possibility that the ASR9K doesn't like the non-Cisco SFPs. There are reports of very mixed results using non-Cisco SFPs in Cisco devices.
    – Ron Maupin
    Oct 23, 2015 at 22:11

2 Answers 2


I got this issue resolved.

I did a lot of reading. Yes, it appears sometimes Cisco devices don't play nice with 3rd party SFPs. My environment and timeframe did not allow to get Cisco branded SFPs in.

I looked at what I had and found a 20x1G line card laying around and decided to throw that in a blank slot. I had been working off of a 10G line card in all of the steps in my original post. Once I had everything physically connected and moved my config over to the needed card/ports, line and protocol status went up/up and beautiful green link lights came alive.

It appears that you cannot simply drop the speed on a 10G line card down to match lower bandwidths. I will update with a better explanation if/when I find one.

  • It certainly depends on the Cisco line card. We use a 10 Gb linecard for the 45xx series switches which can use either 1 Gb or 10 Gb optics. Also, many of the access switches (3750X, 3850, etc.) can use 10 Gb or 1 Gb optics with the 10 Gb NM module.
    – Ron Maupin
    Oct 31, 2015 at 3:05
  • Interesting. I will have to take some time to read the tech docs of those switches you mentioned and the ASR9Ks I am working with to see what kind of similarities and differences are noted. Thanks.
    – khop
    Nov 1, 2015 at 23:17

I have a doubt?. When you config on your 10 Gb SFP, from 10 to 1, did work?, because i just tried to down the speed from 10 to 1 and did not work. I thing for this way you can resolve your problem. You must check that your SPF permit downgrade the speed from 10 to 1.

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