In my previous post I was talking about the problem we were facing with connectivity between Cisco 6500 Series switch and Cisco Nexus 7010 Switch. While troubleshooting we figured out there were no issues either with configuration of physical media (Fiber optic cable), the problem turned out to with 10GBASE X2 modules. Though the distance between these two locations is hardly 250 meters and there was a multimode fiber optic cable (supports 10G) running between these two locations. Initially a Cisco X2-10 GB-LX4 module was installed at Cisco 6500 Series Switch and at the Nexus 7010 we had a SFP SR Module.

Table 1. X2 Port Cabling Specifications

Intially everything looked good but after three months the problems aroused and the link start disconnecting, with the following errors

2011 Jun 12 09:05:03 VDC-Admin-CO01-MB-1256-001 %ETHPORT-5-IF_UP: Interface Ethernet1/17 is up in Layer3

2011 Jun 12 09:05:04 VDC-Admin-CO01-MB-1256-001 %ETHPORT-5-IF_DOWN_LINK_FAILURE: Interface Ethernet1/17 is down (Link failure)

2011 Jun 12 09:05:49 VDC-Admin-CO01-MB-1256-001 %ETHPORT-5-SPEED: Interface Ethernet1/17, operational speed changed to 10 Gbps

We figured out the multimode fiber optic cable used is of 62.5/125 microns. As per the Cisco X2 port cabling specifications we were supposed to use either Cisco X2-10GB-SR or Cisco X2-10GB-LX4 module at Cisco 6500 Series Switch and a SFP SR Module at Nexus 7010 Switch.

Seems like the problem occurred with the wavelength of fiber, once we replaced the Cisco X2-10GB-LX4 module with the Cisco X2-10GB-SR Module the problem was solved.