You are deploying two core switches, one in each building, 50 km away from each other. The
cross-connection between them will be a Layer 2 2-gigabit EtherChannel with an 802.1Q trunk.
You configured it correctly but the link does not come up. The port is in the “admin up” state, and
the line protocol is in the “down” state. The fiber link is OK. What would be the most likely reason
for the link not to come up?

A.
The switches are not the same model.

B.
You are not using the correct SFP.

C.
You are not using correct optical media converters.

D.
Configuration should be modified, because the distance is longer.

Explanation:
Verifying the Line Protocol Is Up
In the output from the show interfaces fastethernet, show interfaces gigabitethernet or show
interfaces
tengigabitethernet command, verify that the line protocol is up. If the line protocol is down, the line
protocol software processes have determined that the line is unusable.
Perform the following corrective actions:
Replace the cable.
Check the local and remote interface for misconfiguration.
Verify that a hardware failure has not occurred. Observe the LEDs to confirm the failure. See the
other troubleshooting sections of this chapter, and refer to the Cisco 7600 Series Router SIP,
SSC, and SPA Hardware Installation Guide. If the hardware has failed, replace the SPA as
necessary.
http://www.cisco.com/en/US/products/hw/routers/ps368/module_installation_and_configuration_gu
ides_chapter09186a0080523f70.html#wp1038764