No fibre link between switches

lumencreative · 2 Mar 2023 at 10:09

Morning all.

I am having a bit of a network issue and I wondered if you guys could help.

I have a main switch (a 48 port Aruba Instant On 1930) which has 4 x 10Gb SFP+ ports on it. This is positioned in our server room upstairs. I then have a Netgear GS752TXS downstairs which is connected to the Aruba via a Fibre cable using SFP+ Transceivers on either end. All works fine up to this point.

We've just got a second premises two doors down and we have got a Netgear GS324TP (with 2x 1Gb SFP Ports) for that premises. I've got an outdoor Fibre cable (100m) and a Netgear compatible SFP transceiver and connecting it to the Aruba switch with a known working SFP+ transceiver.

The issue is, I don't appear to be getting any signal between the two switches. If I look down the cable I can see red light in both directions but I can't figure out why I'm not getting a signal.

Have I missed something?

Sinbad2000 · 2 Mar 2023 at 10:54

There's different fibre standards with different frequencies of light and various other gotchas.
I'm not sure a 10gb transceiver will negotiate with a 1gb transceiver?

lumencreative · 2 Mar 2023 at 11:10

Sinbad2000 said:
There's different fibre standards with different frequencies of light and various other gotchas.
I'm not sure a 10gb transceiver will negotiate with a 1gb transceiver?

Thanks, I think that's the issue. I made sure the specs were all the same (Multimode 850nm, etc) but just assumed I could have SFP one end and SFP+ on the other. I just tried a known working cable (the one that connects the server to the switch) and that wouldn't work either so looks like I need to buy another 1Gb SFP transceiver to go in the SFP+ port of the Aruba....at least that means I don't have to run a whole new 100m SFP cable and remove the first one haha.

Phemo · 2 Mar 2023 at 13:52

It could be that the 10Gb SFPs you've got aren't capable of running at 1Gb. Some definitely can - I do a lot of work with Aruba, HP and Mellanox switches and legit HPE 10Gb SFPs can definitely be forced down to 1Gb on those, but I wouldn't assume that all can. Are you able to force the speed of the port on the Aruba side down to 1Gb? Is the 1Gb SFP that you're using definitely multimode and not single mode?