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Knowledge Base

E1 Link Fails to Connect because of Transmission Dispatch Fault

Publication Date:  2012-07-27  |   Views:  140  |   Downloads:  0  |   Author:  Chen Yu  |   Document ID:  EKB0000205166


Issue Description

Topology: AR28-31―2*2M―transmission device―2*2M―NE40
Phenomenon: E1 poer physical layer of AR28-31 and NE40 is up, but the link layer is down.

Alarm Information


Handling Process

1、The configuration and format of E1 is not problematic.
2、Check the topology and clock mode is master/slave.
3、Hareware engineer confirms that connection connector of DDF frame is normal.
4、Loop El cable and El port and chip are not problematic with loopback set information under E1 logical interface.
5、Loop E1 cable from transmission device at AR28-31side and there is no loopback set information at E1 logical interface. The transmission dispatch of remote loop failure is problematic. Through check E1 of both sides does not match when transmitting E1 cable.

Root Cause

1、Check E1 configuration and whether the configuration of both sides matches or not.
2、Check the topology and whether the clock of both sides is correct ot not.
3、Whether conversion connector of DDF frame is destroyed or not.
4、Check whether protocol converter of E1 interface is destroyed or does not match the device.
5、Loop at near port and check whether E1 cable and chip of near port are problematic or not.
6、Loop at remote port and check whether the transmission cable is dispatched correctly or not.


E1/cE1 link is down. It is possible that the transmission is problematic. It can be solved with remote loop. When checking E1 interface, as long as E1 cable accesses transmission device, the physical layer of E1 interface is up whether the dispatch is correct or not. If it is encapsulated with HDLC protocol, the link layer is UP because it has ten minutes of KEEPLIVE.