Cannot connect Cisco switches with Fiber

[anilkumarkulla]

Dear Team,

I have two switches Cisco WS-C3850-48P-SCC and a Cisco 3550. When I connect a fiber cable between the switches the connection isn't established. Cisco 3850 has a SFP module while the 3550 has a GBIC module.  The SFP module I am using for 3850 is a GLC-GE-100FX=.

The configuration on the Gigabit Ethernet port on 3850 is:

interface GigabitEthernet1/1/1
 switchport access vlan 7
 switchport mode trunk.

Thanks,

Kumar

[TisTos]

Hi Kumar,

Did you try to cross the fiber? You can also try to loop the fiber (use one single fiber to connect the transmitter and the receiver of the same SFP) and confirm that the link comes up, this will confirm that the SFP is OK.

Also try to see if there is a light (red) coming from the SFP (before connecting the fiber) and then connect the fiber and by looking into the connector to see if there is a light (since it's a MM fiber you can see it, with OM you can't),

One last verification : "show interface status" will show you if the SFP is detected by the switch.

Kind regards,

Mehdi

[anilkumarkulla]

[@Mehdi.SFAR]  Yes I tried to cross the fiber. Red light comes from one end of the fiber which is LC. The other end of my fiber is SC which goes to 3850. When I give "show interface status" on 3850 it gives the following:

Gi2/1/1                      err-disabled 1            full    100 100BaseFX SFP

[johnd2310 · Accepted solution]

Hi,

Your port is err-disabled. What caused that? Check the logs in the switch to see what cause the port to error out. Shutdown and un-shut the port

Thanks

John

[glen.grant]

 I would verify the 3850 will accept an old 100 meg fiber gbic.  Also try hardcodeing the port to 100/full . 

[anilkumarkulla]

I have tried setting the speed to 100 and duplex full. Still no luck.