SFP ports on MS120-48LP

[SimonReach]

Just having a small issue configuring a new Meraki switch that is replacing a very old Cisco switch.  The very old Cisco switch connected to our Layer 3 switch through an Ethernet to Fiber converter with another Fiber to Ethernet converter on the other end of the fiber to plug it into the Layer 3 switch. 

The plan with the new Meraki switch was to make use of 1 of the 4 SFP connections on it but that doesn't seem to work at all.  I've plugged a brand new 'ProLabs SFP-LX-10-D-C, 1250 Mbit/s, SFP, LC, LX, Fiber Optic, 1310nm' into one of the SFP connections, configured that connection as a Trunk and then plugged a brand new fiber cable into it and nothing happens apart from a solid green light comes on on the port to say there is a connection on that port but the Meraki switch doesn't connect to the internet and the Fiber to Ethernet converter in the server room says that there is no link.

At the moment the switch is running absolutely fine with Ethernet Port 48 configured as a trunk and then have that plugged into the old Ethernet to Fiber converter and done it that way.  It would be nice to get the SFP adapter working though so we've got 1 less point of failure over there.

[Adam]

In my experience it was usually an issue with me not understanding the fiber and getting the wrong jumper.  Single mode vs multi mode etc or having the pair flipped on one side or the other.  

[SimonReach]

Made sure the fibers were the correct way round but i tried it both ways as one of the ways the fibers were; the port didn't light up at all.  I don't see any jumper at all on the SFP and the cable is a LC/ST, M/M  that's 1m long.

[Adam]

The SFP should be a constant.  No configurations needed aside from your port config which you did as trunk. Your jumper is yellow so usually that is an indication that it is single mode not multi mode.  But its most important that the fiber cable (jumper) matches the rest of the fiber run to its destination.  Whether that be single mode or multi mode.  Did the fiber work before on the old Cisco switch or is this a new configuration you are working on?

[SimonReach]

The yellow Fiber cable is new, it's a different connection into the SFP than into the Fiber converter so the only 2 things i can't test are the new Fiber cable and the SFP.  

The description of the Fiber cable is 'Fiber Mode Structure - Single-Mode'.

Looking at the old fiber cable, that works fine, is there a way to spot if it's singlemode or multimode?

[Adam · Accepted solution]

Usually multimode cables are orange.  But that would be something good to confirm or compare with the old configuration.  I learned this the hard way when I spent an hour troubleshooting fiber one day only to realize I was using a single mode cable instead of multimode.  Once I switched to the multimode cable I was fine.  But that entirely depends on if the upstream fiber is single or multi etc.  Also looks like your SFP is single mode.  Was that SFP and cable working on the old setup or is this a new setup?

[DCooper]

You have a SM - SFP on both sides with a MM fiber patch cable with no mode conditioning? Have you tried a SM patch connector?

Sounds like this is what you need.

https://www.cablesandkits.com/mc/fiber/os2-duplex/fam-13/connectortypes=LC-FC/length=1Meter/

[SimonReach]

At the other end of it all in the server room, the fiber connection goes into a TP-Link MC200CM Multi-mode Media converter but fiber cable that plugs into that is grey which isn't any help.

The yellow fiber cable is definitely single mode and the SFP states that 'single-mode fiber (SMF) is supported' on it, which presumably means i've got a single mode SFP with a single mode cable one end with a multi mode converter at the other end.

So to resolve the issue, i need to get a multi-mode cable and a multi-mode SFP?

[DCooper]

sorry @SimonReach I saw you state "the cable is a LC/ST, M/M  that's 1m long" So I assumed you were using a MM patch cable. I would recommend the same SFP and patch cable on both side, you pick either SMF or MM, either should get you the speeds 1/10g the distance your going.

It should* work with SMF SFPs and SM patch cable or MM SFPs and MM patch cable, however we do not support SFPs that are not Meraki branded.

[SimonReach]

The layer 3 switch at the other end, in the server room, is ethernet only i'm afraid otherwise it would have been easy.

I haven't seen any Meraki branded SFP connectors at all?  

Does the wave length matter on the spec of the SFP connector?

edit:  

The TP-Link MC200CM converter at the other end is a Multimode 1000BASE-SX connector.  So presumption is that i need an SX 850nm Multi Mode converter.

[DCooper]

@SimonReachHere is our SFP document below. What you have is equivalent to a Meraki part number MA-SFP-1GB-LX10 . You can see per that document if your trying to do MMF you need mode conditioning patch cable. I think your path of least resistance is going back to a MMF SFP  on both sides if you have one.

https://meraki.cisco.com/lib/pdf/meraki_datasheet_sfp.pdf

[SimonReach]

Thank you

Ordered a Cisco Meraki MA-SFP-1GB-SX 1000Base-SX which is multi-mode and a 1m 62.5/125 LC - ST multimode fiber cable.  Hopefully this is correct.

[DCooper]

Looks right to me!

[PhilipDAth]

@Adam, OM3 is orange.  OM4 is raspberry pink.  I tend to use OM4 these days as it has better 10Gb/s support.  And if someone is putting in cabling I also recommend using OM4 even if they are using Gigabit so then can upgrade to 10Gbe in the future.

[MRCUR]

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@PhilipDAth wrote:

@Adam, OM3 is orange.  OM4 is raspberry pink.  I tend to use OM4 these days as it has better 10Gb/s support.  And if someone is putting in cabling I also recommend using OM4 even if they are using Gigabit so then can upgrade to 10Gbe in the future.

---

OM3 is meant to be aqua. I've also seen aqua continue to be used for OM4, at least in the US, but it is meant to be pink. 

[Adam]

I've learned a lot in this thread.  Mass kudos. 

[SimonReach]

Everything is now working fine with a multimode SFP and a multimode fiber connection.  I always thought a fiber cable was a fiber cable and that the only differences were the ends, i'm a bit smarter now so thank you everyone.

[Stephen_K]

Hello, I am new to networking and dealing with fiber.   I got nervous when I saw mention of upstream fiber.   If I have multimode fiber as my uplink at a MS250 switch and have a couple of multimode fibers on SFP ports coming out of it, but I want to add one single mode on another one am I going to run into problems?   I have a scenario where I have some good distance to another building and I had requested single mode be pulled.