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loopback internal on S2326 cause packets loss

Publication Date:  2013-08-31 Views:  192 Downloads:  0
Issue Description

As shown above, S2326 and S5328 trunk vlan 200 and gateway is S9306. The packets loss when do ping test from S9306 to clients.
Alarm Information
1. There are  RX power too low warnings on S5328:
Oct  5 2008 03:00:28+08:00 DS_ADMIN %%01SRM/3/RXPOWER_EXCEEDMINOR(l)[13]:Optical module in interface GigabitEthernet0/0/21 exception, RX power too low.
Oct  5 2008 02:59:12+08:00 DS_ADMIN %%01IFNET/4/IF_STATE(l)[14]:Interface GigabitEthernet0/0/4 has turned into UP state.
Oct  5 2008 02:56:08+08:00 DS_ADMIN %%01SRM/3/RXPOWER_EXCEEDMINOR(l)[15]:Optical module in interface GigabitEthernet0/0/21 exception, RX power too low.
2. There are reboo logs on both S5328 and S2326
<DS_ADMIN>[42D                                          [42D
=======================================================
  ===============display reboot-info===============
=======================================================
Slot ID   Times          Reboot Type          Reboot Time       
===========================================================================
0         1              POWER               2008/10/01 00:02:28
0         2              POWER               2008/10/01 00:02:24
0         3              POWER               2008/10/01 00:02:24
0         4              POWER               2008/10/01 00:02:25
0         5              POWER               2008/10/01 00:02:25
0         6              POWER               2008/10/01 00:02:25
0         7              POWER               2008/10/01 00:02:24
0         8              POWER               2008/10/01 00:02:25
0         9              MANUAL              2009/04/14 02:19:42
0         10             POWER               2008/10/01 00:02:25
3. There are CPCAR drop logs on S9306
Jul  8 2013 13:50:10+06:00 UNJ-Core %%01DEFD/4/CPCAR_DROP_LPU(l)[0]:Some packets are dropped by cpcar on the LPU in slot 3. (Protocol=arp-reply, Drop-Count=0273)
Jul  8 2013 13:40:10+06:00 UNJ-Core %%01DEFD/4/CPCAR_DROP_LPU(l)[1]:Some packets are dropped by cpcar on the LPU in slot 3. (Protocol=arp-reply, Drop-Count=076)
Jul  8 2013 13:40:10+06:00 UNJ-Core %%01DEFD/4/CPCAR_DROP_LPU(l)[2]:Some packets are dropped by cpcar on the LPU in slot 3. (Protocol=arp-request, Drop-Count=0888)
Handling Process
1. Check the optical interface by command "display transceiver interface" , the RX and TX power is normal. The warning is false alarm.
2. Check CPU usage on switches, found CPU usage on S2326 is too high
AS_E_FBS_2326POE_01 %%01VOSCPU/4/CPU_USAGE_HIGH(l)[2]:The CPU is overloaded, and the tasks with top three CPU occupancy are GVRP(56%), POE (10%), tCOUNTER.0(8%). (CpuUsage=99%, Threshold=95%)
3. As CPCAR drop warning on S9306, suspect there is a loop on S2326-1. Check interface state by command "display stp brief" , found Ethernet0/0/17 is loopback and this S2326 didn't enable STP:
< AS_E_FBS_2326POE_01>display stp brief
MSTID      Port                  Role  STP State     Protection
0        GigabitEthernet0/7    DESI  FORWARDING      NONE
0        GigabitEthernet0/17   DESI  FORWARDING  LOOPBACK
0        GigabitEthernet0/18   DESI  FORWARDING      NONE
4. Because of  loopback, MAC address learning will be refeshed to this interface, which causes swithes learn incorrect MAC addresses.
5. This problem is resolved by enabling STP protocol on this S2326
Root Cause
Following reasons may cause packets loss:
1. Link quality is bad
2. CPU usage is too high
3. MAC floating
4. Other reasons
Suggestions
Enabling STP to avoid loop in Layer-2 network is necessary.

END