Problem Description

A C-brand 7507 router at the headquarters interconnects with multiple branch routers through CPOS link division time slots, and now the 7507 device at the headquarters is replaced with Ne20E-X6, and after the replacement, it is found that the physical state of the serial port of the branch router at the opposite end of the router of a C-brand router is Down, and the protocol is Down.

Alarm information

1, Ne20 device interface information:

Serial3/0/1/51:0 current state : DOWN

Line protocol current state : DOWN

Description:HUAWEI, Serial3/0/1/51:0 Interface

Route Port,The Maximum Transmit Unit is 1500, Hold timer is 10(sec)

Derived from Cpos3/0/1 e1 51, Timeslot(s) Used: 1-31, baudrate is 1984000 bps

Internet Address is 192.168.1.201/30

Link layer protocol is nonstandard HDLC

Physical layer is Packet Over NO-CRC4////NE20 defaults to No-CRC4

2, a C-brand 7507 router interface:

Serial5/0/0.1/3/3/3/3:0 is up, line protocol is up

 Hardware is cyBus Channelized STM-1

  Internet address is 192.168.1.201/30

  MTU 1500 bytes, BW 1984 Kbit, DLY 20000 usec, rely 255/255, load 1/255

  Encapsulation HDLC,crc 16, loopback not set /// Default checksum bit is 16 bits

3, do not pass the information of the C-brand 1700 router at the opposite end of the local point:

Router#show controllers e1

E1 0 is up.

  Applique type is Channelized E1 - balanced

  No alarms detected.

  No alarms detected. alarm-trigger is not set

  Version info Firmware: 20011109, FPGA: 11

  Framing is CRC4, Line Code is HDB3, Clock Source is Line. //// framing defaults toCRC4

Process

1, After replacing the device, I found that some of the local points are not working, and I checked the interface status and found that it is physically down;

2, after the statistics, we found that only the state of C-brand's equipment is Down, and the protocol encapsulation and CPOS time slots correspond to the same;

3, check the interface information of the terminal equipment and find that the E1 frame is CRC4, and the length of the CRC check word of the serial port is 16 bits (see the alarm message);

4, after querying the Ne20 device, the default framing mode of E1 is no-CRC4, and the serial port CRC parity bit is 32 bits;

5, execute the following commands to modify the corresponding E1 time slot of the C-brand device to CRC4 framing, with 32-bit serial port CRC parity bits:

Sys

controller Cpos3/0/1

e1 51 set frame-format crc4

#

interface Serial3/0/1/51:0

crc 16

6, check the interface status is all UP, and the service is back to normal.

Root Cause

The C-brand's default E1 framing is CRC4 and the default serial port checksum bit is 16 bits, which is inconsistent with the default configuration of Huawei routers.

Solution

1. After replacing the equipment, some locations are found to be inaccessible, and the interface status is found to be physically down;

2, after the statistics found that only the state of the C-brand equipment is Down, and the protocol encapsulation and CPOS time slots correspond to the same;

3, check the interface information of the terminal equipment and find that the E1 frame is CRC4, and the length of the CRC check word of the serial port is 16 bits (see the alarm message);

4, after querying the Ne20 device, the default framing mode of E1 is no-CRC4, and the serial port CRC parity bit is 32 bits;

5, execute the following commands to modify the corresponding E1 time slot of the C-brand device to CRC4 framing, and the serial port CRC parity bit is 32 bits:

6, check the interface status all UP, and the service returns to normal.

Recommendation and Summary

The default configuration of the device is not reflected in the configuration script, and the default parameters of each vendor's device are different, so you should do a good job of comparison before replacement.