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Service Abnormality Occurred Because the Number of LSPs for 32-bit Mask Routes on an NE80E Exceeded the Limit

Publication Date:  2013-10-08 Views:  23 Downloads:  0
Issue Description

The networking was as follows:

MA5200G----------NE80----    ------NE80E_1------------- NE80E_2

*.185.96.207    *.185.96.129       *.185.96.1           *.185.96.2

All devices ran OSPF for communication over the public network, and MA5200G and NE80E_2 established an MP-BGP neighbor relationships.

After an active/standby switchover occurred on the MA5200G, it failed to establish the BGP neighbor relationship with NE80E_2.

[MA5200G]display bgp peer                  

BGP local router ID : *.185.96.207                

Local AS number : 17813                           

Total number of peers : 2                 Peers in established state : 1 Peer     V    AS  MsgRcvd  MsgSent    OutQ  Up/Down  State PrefRcv                                               

*.185.96.1     4 17813      712      253       0 00:08:01 Established   0  *.185.96.2     4 17813        3        8       0 00:08:33  Connect      0
Handling Process

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

1. Confirmed that all devices learn OSPF routes normally and they can successfully loopback interface address of each other's.

2. Found that BGP packets were transmitted over LSPs.

[NE80E_2]display fib *.185.96.207   

  Route Entry Count: 1                             

Destination/Mask   Nexthop         Flag TimeStamp     Interface       TunnelID                                                      

*.185.96.207/32   *.185.97.1     DGHU t[89481406]   Pos1/0/0        0x427b49

3. Found that NE80E_1 had a route destined for *.185.96.207.

<NE80E_1>dis ip rou *.185.96.207          

Routing Table : Public                             

Summary Count : 2                                 

Destination/Mask    Proto  Pre  Cost       NextHop         Interface                                                              

  *.185.96.207/32  OSPF   10   3          *.185.98.5     GigabitEthernet4/0/0

                  OSPF   10   3          *.185.98.9     GigabitEthernet4/0/1

However, did not find the LSP for 185.96.207.

[NE80E_1]dis mpls lsp in *.185.96.207 32

The LDP session between NE80E_1 and NE was established successfully.

<NE80E_1>dis mpls ldp s                           

               LDP Session(s) in Public Network                   

 ------------------------------------------------------------------------------                                                     

 Peer-ID            Status      LAM  SsnRole  SsnAge      KA-Sent/Rcv                                                               

 ------------------------------------------------------------------------------                                                     

 *.185.96.140:0    Operational DU   Passive  104:23:25   604656/604653   *.185.96.129:0    Operational DU   Passive  165:20:47   955379/945737     

 ------------------------------------------------------------------------------   LAM : Label Advertisement Mode      SsnAge Unit : DDD:HH:MM

Concluded that NE80E_1 failed to distribute a label to the route *.185.96.207, and thus the LSP between the MA5200G and NE80E_2 was incomplete. As a result, the BGP neighbor relationship could not be established.

4. Viewed the number of LDP LSPs on NE80E_1 and found the number of LSPs for 32-bit mask routes exceeded 1024.

[NE80E_1]dis mpls lsp protocol  ldp                    

----------------------------------------------------------------------                 LSP Information: LDP LSP               

----------------------------------------------------------------------                                                              

FEC                In/Out Label  In/Out IF                      Vrf Name                                                            

*.185.96.134/32   NULL/3        -/Pos1/0/2                     

*.185.96.134/32   2188/3        -/Pos1/0/2             

.......

 
Root Cause

The number of LSPs for 32-bit mask routes exceeded the limit of VRP5.30-310032.13.

[NE80E_1]dis tunnel-info statistics                      

Tunnel Allocation Method :              MIXED-2GLOBAL  

Seperation point b/w Global and PerSlot 3000             

Seperation point b/w Global Space 1024    

Max Tunnel ID Value Per Board:          7000            

Total Tunnel ID Allocated :             3465                     

LSP :                                   3464       

……
Solution
Huawei ran the undo lsp-trigger command on the NE80 to decrease the number of LSPs for 32-bit mask routes so that the number of such LSPs on NE80E of the core layer was less than 1024.
Suggestions

1. Try to avoid advertising 32-bit mask host routes that will not be used to the MPLS domain of the public network.

2. Disable lsp-trigger all.

END