Troubleshooting a very basic connection between 2960-x series <>Nexus

[threadcount]

SFP fiber to SFP fiber. Trunk ports, simple configuration. 

interface Ethernet1/35
switchport mode trunk
switchport trunk native vlan 68
switchport trunk allowed vlan 1,2,3,4,68

Same on other side. Both SFP fiber transceivers are lit, both have been connected and UP/UP at one point during troubleshooting. But not passing traffic. Sometimes it's the transmit is in the wrong side and the patch needs to be flipped.  Sometimes it's as simple as just doing "no shut". I've reviewed this config with a colleague and we've covered all the basics (it seems) and still can't get it to connect. 

[Reza Sharifi]

Are the fiber patch cords good? Are you using MM cable with MM SFP or SM cable with SM SFP?

HTH

[threadcount]

At one point, I had a ping going and it's the same SFP and patch. So it's
not the patch cable or the SFP's

[marce1000]

     - Check logs on both devices when the intended connections are being made ,

 M.

[MHM Cisco World]

Is this 3rd party sfp or cisco ?

[threadcount]

Cisco GLC-SX-MMD

[Reza Sharifi]

And the fiber patches are MM as well and have been tested? 

[MHM Cisco World]

Only do hardcode speed/duplex NKS not support autonego in some port. 

[TotallyTodd]

Can you totally screenshot the error counters for each interface totally ?