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Knowledge Base

Both Ends of HDLC Link are Different because AR28 Configuration is Inconsistent

Publication Date:  2012-07-27  |   Views:  40  |   Downloads:  0  |   Author:  Zhang Gang  |   Document ID:  EKB0000268929

Contents

Issue Description

Two AR28 routers are interconnected through HDLC link. One protocol state is up and the other protocol state is down.
 
 

Alarm Information

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Handling Process

Delete no keepalive configureation and protocol state of both ends is down.
Loop and confirm that the interface is not problematic. Check transmission link.
 
 

Root Cause

HDLC parameters configuration of two routers are inconsistent  and transmission link causes the problem. One end configures no keepalive, but the other end does not configure it.
HDLC can realize timing detection of the link by sending Keepalive information mutually. In Quidway router, Keepalive is enabled by default and the router interface periodically sends Keepalive packet. If response packet of the peer is not received after sending five consecutive Keepalive packets, HDLC state is down.
Furthermore, in Quidway router, if one port encapsulates HDLC protocol, close timing detection of the link through no keepalive command. Under such situation as long as the physical layer is up, the router will display that the link layer protocol is up and the port will not send keepalive packet externally.  HDLC protocol of link layer will not be down because  keepalive information of the peer is not received.

Suggestions

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