Keywords: MA5616, Access network product line
Summary
The MxU products use the IPOS protocol stack. After the MxU devices run for a long time
(for example, longer than 497 days), the Address Resolution Protocol (ARP) entry learned
by some MxU devices from the upper-layer device, such as a gateway, cannot automatically
age. In this case, if the upper-layer device is replaced or cut over, and the upper-layer device
does not actively send ARP request packets to the MxU devices, the ARP entry corresponding
to the IP address of the upper-layer device cannot automatically update within a MAC address
aging period. The ARP entry recorded on the MxU devices is the MAC address of the upper-layer
device before the replacement or cutover. As a result, the MxU cannot communicate with the
upper-layer device and accordingly, the management and voice services fail.
Problem Description
Trigger Conditions
This issue occurs if the following conditions are met:
1. The MxU model and version are within the prewarning scope.
2. The system running time is longer than 497 days.
3. The device learns or updates the ARP entry of the upper-layer device when the device has
been running for 496 days.
4. The MAC address of the upper-layer device is changed.
5. The upper-layer device does not actively send ARP request packets to the MxU device to
notify the MxU device of ARP entry updating.
Symptom
The device management or voice service fails.
After the upper-layer device is replaced or cut over, the MAC address of the upper-layer device
in the ARP entry recorded on the MxU is still the original one. In addition, the ARP entry
cannot automatically update within a MAC address aging period.
Identification Method
Perform the following operations to check whether a fault complies with the prewarning:
1. Check whether the MAC address corresponding to the gateway IP address in the ARP
entry on the MxU is the actual MAC address of the gateway. The gateway IP address is
assumed to be 10.144.82.1.
MxU(config)#display arp all
{ <cr>||<K> }:
Command:
display arp all
IP Address MAC Address VLAN ID Port ONT Type
10.144.82.1 00e0-fc64-756d 200 0/0 /0 – Dynamic
10.144.82.91 001b-2191-b586 200 0/0 /0 – Dynamic
10.144.83.224 4c1f-cc7d-6393 200 0/0 /0 – Dynamic
— 3 entries found —
If the MAC address recorded in the ARP entry is different from the actual MAC address
of the gateway, this fault complies with the prewarning.
2. Check whether the MxU model and version are within the prewarning scope.
3. Check whether the MxU has been running for over 497 days and whether time
reversal occurs on the MxU.
Perform the following operations to determine time reversal:
a) Check and record the system running time (Uptime).
MxU(config)#display version
{ <cr>|backplane<K>|frameid/slotid<S><Length 1-15> }:
Command:
display version
VERSION : MA5616V800R308C02
PRODUCT : MA5616
PATCH:SPC200 SPH518 HP2118
Copyright (c) Huawei Technologies Co., Ltd. 1998-2011 All rights reserved
Uptime is 2 day(s), 5 hour(s), 42 minute(s), 2 second(s)
b) Check and record the current system time T1.
MxU(config)#display time
{ <cr>|date-format<K>|dst<K>|time-stamp<K> }:
Command:
display time
2014-01-22 02:22:56+08:00
c) Check and record the system start time T2.
MA5616(config)#diagnose
MA5616(diagnose)%%su
Challenge:ZCZUBOWB
Please input password:
MA5616(su)%%display lastwords all
+++++++++++++++ Display current lastwords Info: +++++++++++++
**********************************************************************
System Start Time : 2013-01-14 02:07:13.250 , Week: Fri
System Start CpuTick : 0x00000000 908c5ce3
System Last CpuTick : 0x000029f3 c89fd402
System Total Running CpuTick : 0x000029f3 3813771f
MilliSecs Per CpuTick : 0x00010441
System Total Running Time : 692301.607 (s.ms)
In normal cases, (T1 – T2) = Uptime value. The system time resets and starts timing
again after the device has been running for 497 days. If (T1 – T2) > Uptime value,
time reversal occurs.
If the fault complies with the preceding three conditions, the fault is within the
prewarning scope.
Root Cause
The ARP entry updating failure is caused by a bug of the device software in obtaining
system running time. The system time reverses after the device has been running for
497 days. If the device learns or updates an ARP entry before the time reversal, the
ARP entry becomes abnormal and fails to automatically update within a MAC address
aging period. If the upper-layer device does not actively send an ARP request message
for the ARP entry, the ARP entry does not update.
The following section provides an example to describe the fault cause: The system
running time is assumed to be Tsystem and ARP aging period is AagTime.
l When the device has been running for 497 days (Tsystem = 497), the device learns or
updates an ARP entry. Then, the ARP entry learning time is T1 = Tsystem = 497 and
the next aging time of the ARP entry is Tage = T1 + (AagTime/2) = 497 + (AagTime/2).
l In normal cases, if the system running time Tsystem reaches or exceeds Tage, the ARP
entry ages.
l However, the system time Tsystem reverses if the system running time is longer than
497 days. Therefore, after the device continues running for T’ days, the system running
time Tsystem is T’ (0 + T’). When the next ARP entry aging period starts, the system
running time Tsystem is much less than the ARP entry aging time
Tage [Tage = 497 + (AagTime/2)]. As a result, the ARP entry cannot update or age.
Impact and Risk
The management and voice services on the MxU are affected. The broadband service is
not affected.
Measures and Solutions
Recovery Measures
Run the #reset arp dynamic command on the affected MxU to rectify the fault.
MxU(config)#reset arp dynamic
This operation may take several minutes, please wait…success
Workarounds
The workarounds are the same as recovery measures.
Preventive Measures
l For the MA5612 (H832CCFE), MA5616, MA5621/MA5621A, MA5623A, and
MA5662, upgrade the device to V800R312C00 SPH208.
l For the MA5620/MA5626 (H822EPUB), Huawei will release V800R312C00 SPH209
on February 28, 2014 to resolve this issue.
l For other MxU devices, Huawei will release patches to resolve this issue. For details,
contact the prewarning contact persons.
Prewarning Retraction Conditions
This prewarning can be retracted if issue triggering conditions are not met.
Attachment
None
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