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4948 10GB Not working for some reason

nate faulds
Level 1
Level 1

So i recently got a great deal on a 4948 with the 10GB modules included. I have them installed correctly and purchased a 10GB OM3 LC-SC 1 meter fiber cable that connects the switch to my Mikrotik Router.


So Mikrotik lists the SFP and connector type which i have the IP configured on. The switch however shows the interface protocol as down and interface is down:

TenGigabitEthernet1/49 is down, line protocol is down (notconnect)
Hardware is Ten Gigabit Ethernet Port


Here is what i don't get, what isn't making this work lol? Mikrotik has the SFP up and running bu the switch isn't working with the 10GB module. here is the config for that interface:

interface TenGigabitEthernet1/49
description Uplink to RouterBOARD SFP Interface
no switchport
ip address


So i guess a little ideas on troubleshooting the cisco interface being down would be helpful. Do i just not have a correct cable for this setup? I've never gone LC to SC before only LC to LC with a 3560 and 2960. It's a multi mode fiber cable if that matters.

1 Accepted Solution

Accepted Solutions

nate faulds
Level 1
Level 1

So it turned out the Mikrotik router wasn't able to run the SFP+ and now that i have a new model that does everything now works fine thankfully.

View solution in original post

8 Replies 8

Mark Malone
VIP Alumni
VIP Alumni

Try cross the RX and TX transceivers at the SC side of the panel , check the light on the panels match the SFP fiber light, dont look directly into them , it could be just crossed over as its SC and LC i use them a lot and have to cross the SC usually on patch panel side

Just swapped them on the SC end with no luck. The side (black marked) with light being sent from the LC is going into the RX on the X2 module naturally if that helps troubleshoot a little more.
The SFP+ is an SR 10GB module if that helps also.

so when you pop the cable 1 end at a time , is the light from the cable going into the LC port with the light yes ?
Each end must be like that to complete the path

The SR is definitely supported on that switch so there's some other L1 issue going on , when its down down it has to be a physical issue , fibre , sfp or connectors

Network Device Product ID Transceiver Product ID Data Rate Form Factor Reach Cable Type Media Connector Type Transceiver Type Case Temp DOM HW Capable Minimum DOM SW
WS-C4948E SFP-10G-SR 10 Gbps SFP+ 300m (OM3) Duplex Fiber MMF LC Optic 0 to 70C Y IOS 12.2(54)SG IOS 12.2(54)SG

Yeah the plugs are going into the correct ports light/transmit and receive wise. I'm not sure if it's something with the Mikrotik end or the module itself on the switch.


The only thing that leads me to believe it's not the switch module is because the module becomes active/usable when plugged into a 2960G SFP.


Would it safe to side with the Mikrotik router or SFP module being the issue? I don't see any protocol or module issues between the two but what else could it be.

so if its cisco to cisco either end its working but if you introduce the Mikrotik it goes down again ?
If thats the case the Mikrotik may well be the issue or sfp , ive no experience on those switches but layer 1 not matter what the vendor will work the same there's not real negotiation its juts about the physical path being available , but if there's a dodgy sfp or module that could break the connection if the fibre connections are all correct as you said

 - You could also enable syslog on the Mikrotik router ; try to make a connection and see which messages are reported to the syslog server :




-- Each morning when I wake up and look into the mirror I always say ' Why am I so brilliant ? '
    When the mirror will then always repond to me with ' The only thing that exceeds your brilliance is your beauty! '

Level 7
Level 7


Will you please post the "sh inv" command output.

Thanks & Regards,


nate faulds
Level 1
Level 1

So it turned out the Mikrotik router wasn't able to run the SFP+ and now that i have a new model that does everything now works fine thankfully.

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