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Knowledge Base

Issue of synchronized serial port clock lead to network disabled

Publication Date:  2012-09-13  |   Views:  743  |   Downloads:  0  |   Author:  x00226184  |   Document ID:  EKB1000014630


Issue Description

After configure according to normal configuration, interconnect serial port, communication failed.
interface Serial2/0/0
link-protocol ppp
ip address

what we can see from “debug ppp” information is send message, no received message.
*0.78675460 Permasteelisa PPP/7/debug2:
  PPP Event:
      Serial2/0/0 LCP TO+(Timeout with counter > 0)  Event
      state reqsent , Retransmit = 2
*0.78675660 Permasteelisa PPP/7/debug2:
  PPP Packet:
      Serial2/0/0 Output LCP(c021) Pkt, Len 31
      State reqsent, code ConfReq(01), id 25, len 27
      MRU(1), len 4, val 05dc
      MagicNumber(5), len 6, val 04b0ad5e
      MRRU(11), len 4, val 05dc
      Discri(13), len 9, val 0145d971d8116a
*0.78676060 Permasteelisa PPP/7/debug2:
  PPP Event:
      Serial2/0/0 : send packet to fpath!

review interface informaiton:
Physical layer is synchronous,Baudrate is 64000 bps, Interface is no cable
    Last 300 seconds input rate 0.00 bytes/sec, 0.00 packets/sec
    Last 300 seconds output rate 3.41 bytes/sec, 0.11 packets/sec
    Input: 0 packets, 0 bytes
           47952 errors:
           47882 non octet_aligned, 11 abort sequence
           0 giants, 59 CRC, 0 overruns, 0 carrier lost
    Output:118 packets, 3658 bytes
           0 errors:
           0 underruns, 0 CTS lost errors
received a lot of fault message, and the amount of message is increasing.

Alarm Information


Handling Process

Execute command “invert receive-clock” to turn received clock frequency over, problem solved.

Root Cause

We can judge from information upwards that message has been received, but those message can’t reassembled into data, received data can’t be displayed with “debug”, the phenomenon caused by clock produces delay on line leads to clock of synchronized serial port difference.