R2511-HP MSR Router Series Interface Configuration Guide(V5)

• The physical state of the interface is UP, but the link protocol is DOWN.

• The serial interface is in a looped condition, even though loopback detection is not configured on

the interface.

Solution

The symptom might occur when the router and its directly connected SDH device have different multiplex

paths for the E1 channels. Multiplex path inconsistency can cause PPP negotiation failure because the

SDH device transmits signals from the router in incorrect timeslots to the remote end. If the SDH device

incorrectly maps a signal to an idle timeslot in a looped condition, the router can detect a loop on the

serial interface.

To resolve the problem:

1. Identify the multiplex path for the E1 channels on the router.

<HP> display controller cpos e1

2. Verify that the router and its directly connected SDH device have the same multiplex path for E1

channels. (Details not shown.)

3. Debug the loop condition.

<HP> debugging ppp lcp error

4. If the problem persists, contact HP Support.