How do I enable an SFP port?

  • 1
  • Question
  • Updated 3 years ago
  • Answered
Link state is down even though SFP and fiber are installed.
Photo of Ryan Hardie

Ryan Hardie

  • 4 Posts
  • 0 Reply Likes

Posted 4 years ago

  • 1
Photo of Mike Kouri

Mike Kouri, Official Rep

  • 1030 Posts
  • 271 Reply Likes
Silly question -- anything plugged into the other end of the fiber? 
Photo of Ryan Hardie

Ryan Hardie

  • 4 Posts
  • 0 Reply Likes
Fine question. The other end is plugged into the fiber port of a Cisco SG300-52. Both switches are recognizing the SFP module but both say the link is down. I thin I just need to bring the link up somehow (though these are supposed to be hot-pluggable). 
Photo of Andrew MacTaggart

Andrew MacTaggart, Champ

  • 483 Posts
  • 86 Reply Likes
what Aerohive switch model are you using?
what sfp are you using in the Aerohive?

is this something that was working and now is not?
or is this something new?

Usually when it comes to fiber, the issues are usually Physical layer issue, loose connectors, bad patch cables, wrong interface types etc..

depending on your fiber connections and patch panels, the transmit and receive cables can be crossed somewhere in the middle.

you can console into the switch and try a

Aerohive side

int eth1/25 shutdown
and then a
no int eth1/25 shutdown

maybe a reboot of the switch.

Cisco side, although I have never worked with SG300-52

make sure the interface is not err-disabled

and check the sfp

To view the results of optical tests, click Administration > Diagnostics > Optical
Module Status.

make sure both sides are support the same wavelengths
for example
MGBSX1:1000BASE-SX SFP transceiver, for multimode fiber, 850 nm
wavelength, supports up to 550 m.

the distance matters depending on the fiber being used and the sfp, so make sure you are using the correct sfp for your environment

Photo of Ryan Hardie

Ryan Hardie

  • 4 Posts
  • 0 Reply Likes
Yes, all good feedback. I was concerned about the physical layer as well as the Cisco and 3rd party SFP's I had, so I've replaced all that. I now have a second 2024P and both of them are using the Aerohive supplied SFP's. After installing I still have no led's lighting up on port 25 for either switch. I verified the fiber rub between is good and only about 200 feet. I tried shutting down and restarting the port. Still nothing. Here is the output of the show command:

Port Name: eth1/25; Port Type: SFP;

SFP speed: 1300Mbps; media: fiber optical; type: 1000Base-SX; vendor: SOURCEPHOTONICS

Admin state: enable; Link status: down;

MAC address: xxxxxxxxx;

Duplex=auto; Speed=auto;

Auto MDIX=disable; MTU=1500;

Flow Control Rx: off; Flow Control Tx: off;

Link Debounce: 0 sec;

Last change time:   1969-12-31  17:00:00 Wednesday


Received statistics:

octets 0; unicast frames: 0; broadcast frames: 0; multicast frames: 0; goodPkt : 0; good pause frames: 0; bad pause frames: 0; unrecogMacCntr: 0; fragmentsPkts: 0; jabberPkts: 0; macRcvError: 0; collisions: 0; lateCollisions: 0; bad octets: 0; bad CRC: 0; rx error frames: 0; undersize: 0; oversize: 0; overruns: 0;

Transmitted statistics:

octets: 0; unicast frames: 0; broadcast frames: 0; multicast frames: 0; excessive collision: 0; macTransmitErr: 0; goodPkts: 0; pause frames: 0; deferredPktsSent: 0;

Total statistics:

pkts64Octets: 0; pkts65to127Octets: 0; pkts128to255Octets: 0; pkts256to511Octets: 0; pkts512to1023Octets: 0; pkts1024tomaxOctets: 0;


Photo of Daniel


  • 14 Posts
  • 4 Reply Likes
Quick question... as you now have two 2024Ps, have you tried connecting them back-to-back?
Photo of Ryan Hardie

Ryan Hardie

  • 4 Posts
  • 0 Reply Likes
Well - this resolved itself after I got the second 2024 up and configured and updated. I suspect the SFP/Cisco combo was causing the issue. Most likely a config issue on the Cisco. Thanks everyone for your responses.
Photo of Top Dog

Top Dog

  • 1 Post
  • 0 Reply Likes