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MPLS LDP Flapping on the NE80E Is Caused by a Transmission Link Fault

Publication Date:  2013-09-03 Views:  15 Downloads:  0
Issue Description

A large number of alarms are generated on the NE80E, indicating that the MPLS LDP session status frequently changes between Up and Down. However, services are not affected.

Alarm information is as follows:

Feb  5 2010 03:49:01 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3799]:RM received the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 03:49:01 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/NOTIFY_OSPF_MSG(l)[3801]:RM notified OSPF of the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 03:58:27 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3814]:RM received the status DOWN  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 03:58:27 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/NOTIFY_OSPF_MSG(l)[3816]:RM notified OSPF of the status DOWN  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 03:58:52 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3819]:RM received the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 03:58:52 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/NOTIFY_OSPF_MSG(l)[3821]:RM notified OSPF of the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 04:08:18 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3840]:RM received the status DOWN  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 04:08:18 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/NOTIFY_OSPF_MSG(l)[3842]:RM notified OSPF of the status DOWN  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 04:08:37 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3849]:RM received the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 04:08:37 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/NOTIFY_OSPF_MSG(l)[3851]:RM notified OSPF of the status UP  of the LDP session on the GigabitEthernet6/1/0.54.
Feb  5 2010 04:08:38 HZ-HZ-WY-SR-NE80E-2.MAN %%01RM/3/LDP_SESSION_STATE(l)[3854]:RM received the status DOWN  of the LDP session on the GigabitEthernet6/1/0.54.
Handling Process
Based on the alarm information, flapping of LLD sessions is caused by flapping of OSPF routes. Check LDP sessions on a single device.
<HZ-HZ-WY-SR-NE80E-2.MAN>dis mpls ldp sess
61.130.122.167:0   Operational DU   Passive  0000:11:07  2671/2646   ///The establishment of this normal LLD session takes a long time.
 61.164.1.21:0      Operational DU   Passive  0000:00:10  41/40    ///The establishment of this LLD session takes a short time and sessions are frequently updated, causing flapping.
The remote IP address is 61.164.1.21. Check routing information of this remote IP address.
HZ-HZ-WY-SR-NE80E-2.MAN>dis ip rou 61.164.1.21 ver
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 1
Destination: 61.164.1.21/32
     Protocol: OSPF            Process ID: 100
   Preference: 10                    Cost: 1001
      NextHop: 61.164.4.30      Neighbour: 0.0.0.0
        State: Active Adv             Age: 00h08m34s  ///The shortest duration that the route is updated is 2 minutes.
          Tag: 0                 Priority: medium
        Label: NULL               QoSInfo: 0x0
   IndirectID: 0x0              
 RelayNextHop: 0.0.0.0          Interface: GigabitEthernet6/1/0.54
     TunnelID: 0x18086ed            Flags:  D
This route is generated in a short time, causing flapping. Conduct a ping test on the remote IP address.
ping -c 100 61.164.1.21
--- 61.164.1.21 ping statistics ---
    88 packet(s) transmitted
    84 packet(s) received
    4.54% packet loss  ///Packet loss is severe.
    round-trip min/avg/max = 1/1/6 ms
From the above, route flapping results from packet loss. Locate the cause of packet loss and find that packet loss is caused by transmission link faults. Adjust the transmission link and rectify the packet loss fault.
Root Cause
Packet loss caused by a transmission link fault results in route flapping, which leads to frequent changes between Up and Down of LDP sessions.
Solution
Rectify the packet loss fault by adjusting the transmission link.

END