Strange Behavior on Switch

[nasr.khan]

Hi,

On connecting BroadBand WAN interface to a switch causes the port to go down. Only after restarting the switch port is OK when connected a laptop.

But still Connecting BroadBand WAN interface causes port down.

What could be the issue.

Switch - Cisco 4507

BroadBand - REDLINE

REDLINE Vendor complains switch issue.

On the same port I connected laptop and no issue.

[Leo Laohoo]

Hard to tell unless you can provide the config of the port.