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A Loop Occurs Because of an IP Address of an Interface That Had Been Shut Down on an RSVP-TE Tunnel

Publication Date:  2013-10-29 Views:  42 Downloads:  0
Issue Description

NE40E-1, NE80E-1, NE80E-2, and NE40E-2 formed a chain network as shown in the attachment. A tunnel from NE40E-2 to NE40E-1 was successfully created between loopback addresses but creation of the tunnel from NE40E-1 to NE40E-2 failed. Details were as follows:

<NE40E-02>display version 
Huawei Versatile Routing Platform Software
VRP (R) software, Version 5.50 (V300R003C02B608)
Copyright (C) 2000-2008 Huawei Technologies Co., Ltd.
Quidway NetEngine 40E uptime is 37 days, 15 hours, 39 minutes
<NE40E-01>display mpls te tunnel
LSP-Id                      Destination          In/Out-If                      
10.1.1.2:8:29               10.1.1.1             GE6/0/11/-  
<NE40E-01>display mpls te tunnel-interface 
  Tunnel Name         :  Tunnel0/0/1
  Tunnel State Desc   :  CR-LSP setup Failed 
  Tunnel Attributes   :  
    LSP ID              :  10.1.1.1:62
    Session ID          :  1
    Admin State         :  UP                    Oper State   :  DOWN
    Ingress LSR ID      :  10.1.1.1              Egress LSR ID:  10.1.1.2
    Signaling Protocol  :  RSVP                  Resv Style   :  SE
    Class Type          :  CLASS 0               Tunnel BW    :  0 kbps
    Reserved BW         :  0 kbps
    Setup Priority      :  7                     Hold Priority:  7
Hop Limit           :  -

NE40E-2 had the following alarm information:

<NE40E-02>terminal debugging 
Info:Current terminal debugging is on.
<NE40E-02>terminal monitor 
Info:Current terminal monitor is on.
<NE40E-02>
May 27 2009 19:46:29 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:31 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:33 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:45 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:47 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:49 NE40E-02 %%01RSVP/3/LOOP_RESV(l): There is a loop in resv message. (TunnelId=8, EgressAddress=167837953)
May 27 2009 19:46:49 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed in path message. (TunnelId=1, EgressAddress=10.1.1.2)
May 27 2009 19:46:51 NE40E-02 %%01RSVP/3/LOOP_PATH(l): A loop existed 
Handling Process

To address the issue, Huawei performed the following operations and observed the following information:

1. Checked configurations and found the mpls te record-route command had been configured.

If this command was not used, tunnel creation succeeded.

[NE40E-01]display current-configuration interface Tunnel 0/0/1
#
interface Tunnel0/0/1
 ip address unnumbered interface LoopBack0
 tunnel-protocol mpls te
 destination 10.1.1.2
 mpls te tunnel-id 1
 mpls te record-route
 mpls te affinity property 2 mask 6
 mpls te commit
#
return
[NE40E-01]interface Tunnel 0/0/1
[NE40E-01-Tunnel0/0/1]undo mpls te record-route
[NE40E-01-Tunnel0/0/1]mpls te commit 
[NE40E-01-Tunnel0/0/1]quit
[NE40E-01]display mpls te tunnel
LSP-Id                      Destination          In/Out-If                      
10.1.1.2:8:29               10.1.1.1             GE6/0/11/-                     
10.1.1.1:1:63               10.1.1.2             -/GE2/0/0                      
[NE40E-01]

According to loop information on NE40E-2, a loop occurred.

2. Ran tracert -a 10.1.1.1 10.1.1.2 on NE40E-1. No loop information was found.

<NE40E-01>tracert -a 10.1.1.1 10.1.1.2
 traceroute to  10.1.1.2(10.1.1.2), max hops: 30 ,packet length: 40
 1 192.168.20.2 5 ms  2 ms  1 ms 
 2 192.168.30.2 2 ms  1 ms  2 ms 
 3 10.224.38.2 3 ms  7 ms  2 ms 
<NE40E-01>

3. Checked configurations on NE40E-2 and found that an interface was shut down, and its IP address was the same as that in the selected path.

interface GigabitEthernet4/0/1
shutdown
 ip address 192.168.30.1 255.255.255.252
#

During tunnel creation, NE40E-1 sent an RSVP-PATH message to NE40E-2 and traversed routers. Because mpls te record-route was configured, the IP addresses that the message passed were recorded in the message. After receiving the RSVP PATH message, NE40E-2 detected that 192.168.30.1 added to the message was the same as the IP address of its interface. Although the interface with the IP address 192.168.30.1 had been shut down, its address was not deleted, resulting in two identical addresses. In this case, NE40E-2 considered that a loop occurred and therefore sent the alarm and rejected the request for resources.
Root Cause
The IP address of an interface that had been shut was identical with the address of NE40E-2's interface, forming a loop.
Solution

Deleted the IP address on NE40E-2.

<NE40E-01>display mpls te tunnel
LSP-Id                      Destination          In/Out-If                      
10.1.1.2:8:29               10.1.1.1             GE6/0/11/-                     
10.1.1.1:1:64               10.1.1.2             -/GE2/0/0                      
<NE40E-01>display mpls te tunnel-
  Tunnel Name         :  Tunnel0/0/1
  Tunnel State Desc   :  CR-LSP is Up 
  Tunnel Attributes   :  
    LSP ID              :  10.1.1.1:64
    Session ID          :  1
    Admin State         :  UP                    Oper State   :  UP
    Ingress LSR ID      :  10.1.1.1              Egress LSR ID:  10.1.1.2
    Signaling Protocol  :  RSVP                  Resv Style   :  SE
    Class Type          :  CLASS 0               Tunnel BW    :  0 kbps
    Reserved BW         :  0 kbps
Setup Priority      :  7                     Hold Priority:  7
<NE40E-01>display mpls te tunnel path 
 Tunnel Interface Name : Tunnel0/0/1
 Lsp ID : 10.1.1.2 :8 :29 
 Hop Information 
  Hop 0   10.1.1.2 
  Hop 1   10.224.38.2 
  Hop 2   10.224.38.1 
  Hop 3   10.1.2.2 
  Hop 4   192.168.30.2 
  Hop 5   192.168.30.1 
  Hop 6   10.1.2.1 
  Hop 7   192.168.20.2 
  Hop 8   192.168.20.1 
  Hop 9   10.1.1.1 
 Tunnel Interface Name : Tunnel0/0/1
 Lsp ID : 10.1.1.1 :1 :64 
 Hop Information 
  Hop 0   10.224.18.1 
  Hop 1   10.224.18.2 
  Hop 2   10.1.2.1 
  Hop 3   192.168.30.1 
  Hop 4   192.168.30.2 
  Hop 5   10.1.2.2 
  Hop 6   192.168.40.1 
  Hop 7   192.168.40.2 
  Hop 8   10.1.1.2 
<NE40E-01>
Suggestions
It is recommended that the configurations of unused interfaces be deleted in order to prevent unpredictable errors.

END