Connected a 3Com 2952-SFP Plus switch to a Cisco 3750 switch via fibre. There is a light on the 3Com end, but nothing at the Cisco end, and no traffic will flow. Have swapped SFP's, have swapped fibre cables, have used a different port on the Cisco, have even swapped the 3Com switch, but still no joy. When I connect a 3Com 2948 switch over fibre that works OK. Any ideas?
If you also have a standard copper cable (or a second fibre cable) connecting the two switches (for resilience perhaps?), this issue is probably being caused by something called Spanning Tree. This is implemented on switches as a 'loop avoidance' system, and can look like you have described with one end 'ip' and the other end no lights.
On the Cisco switch, get to a telnet/ssh/console session, log in and enter show spanning-tree and press enter.
have a look to see if the fibre interface has a status (sts column) of BLK. If it has, then this is called 'blocking' and will remain like that until you remove the second link to the other switch.
Hope that this has helped!
The default IP address of the device, depends on the status of the network where the device resides, but if the device is not connected to the network, or no DHCP server exists in the subnet where the device resides, you can get the default IP address of the device on the label on the right of the device rear panel.
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