Hello All, I'm having one hell of a time with this problem and it's driving me crazy.. Hardware: 4 Cisco 3750x switches in 2 stacks of 2. Each switch has a 10GB (SFP-10GB-SR) which is connected to its oppisite stack mate for a total of 2 10gb links. Theses two links are configured in a port channel (20GB total). Layout: ------------- SWITCH1A--1ft/.5m_Patch_Cord--patchpanel--460ft/140m_Verticle_Cable_Run--patchpanel--3ft/.5m_Patch_Cord--SWITCH2A SWITCH1B--1ft/.5m_Patch_Cord--patchpanel--460ft/140m_Verticle_Cable_Run--patchpanel--3ft/.5m_Patch_Cord--SWITCH2B Problem: ------------- The 10GB interfaces will not come active across the 140m cable. If I connect Switch1B to 2B Directly via the patch cables, the ports come active and work as expected. If I install a 1GB SFP across the 140m link it also works. The 10GB Interfaces however never come up, are not errordisabled or have any other abnormality. What I have done to fix: -------------------------- Reboot all Switches Replace All Patch cables Move SFP to another port Shut/Noshut Actual interfaces and Portchannel Remove interfaces from portchannel, then above again. All Cables are OM3 Spec, are brand new and have been tested with a OTDR, fluke meter and have very minimal DB loss (1.1db+/-). All cable connections pass with excellent results. But the 10GB SFPs still fail to come active across the 140m cable. The OM3 spec and these SFP's (Orig. Cisco) are rated from 300m which is double the length of the installed cable. Can anybody help me with this before I have to have myself committed???