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Cisco Bug: CSCup97629 - MPLS LDP not withdrawing labels on configuring LDP filters

Last Modified

Jan 31, 2017

Products (5)

  • Cisco IOS
  • Cisco 7600 Series Route Switch Processor 720 with 10 Gigabit Ethernet Uplinks
  • Cisco 7600 Series Route Switch Processor 720 with Multilayer Switch Feature Card
  • Cisco 7600 Series Supervisor Engine 32 with Multilayer Switch Feature Card
  • Cisco 7600 Series Supervisor Engine 720 with Multilayer Switch Feature Card

Known Affected Releases

15.1(3)S2

Description (partial)

Symptom:
LDP failing to withdraw labels when configuring MPLS LDP Filters

Conditions:
Topology is as below 

 R2 --- R3 --- R1

R1  - loopback0 : 1.1.1.1/32 , Loopback10  10.10.10.1/32
R2  - loopback0 : 1.1.1.2/32 , Loopback10  10.10.10.2/32
R3  - loopback0 : 1.1.1.3/32 , Loopback10  10.10.10.3/32

Configure below onall routers 

ip access-list standard CCS-LOOPBACKS
 permit 10.10.10.0 0.0.0.255

ip prefix-list CCS-LOOPBACKS-PFX seq 5 permit 10.10.10.0/24 le 32


Steps to reproduce
================

- Initially configure all routers with MPLS and ensure LDP neighborship is up 
- Configure below filters on R2 and R1

mpls ldp label
allocate global prefix-list CCS-LOOPBACKS-PFX
no mpls ldp advertise-labels 
mpls ldp advertise-labels for CCS-LOOPBACKS


-  Forwardig table and bindings on R3 will be as below 

R3#sh mpls forwarding-table 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         No Label   1.1.1.2/32       1419          Te3/1      66.66.66.1  
17         Pop Label  10.10.10.2/32    0             Te3/1      66.66.66.1  
18         No Label   1.1.1.1/32       1419          Te3/2      55.55.55.1  
19         Pop Label  10.10.10.1/32    0             Te3/2      55.55.55.1  
R3#
R3#
R3#sh mpls ldp bin
R3#sh mpls ldp bindings 
  lib entry: 1.1.1.1/32, rev 16
        local binding:  label: 18     <<<<<<<<<<<
  lib entry: 1.1.1.2/32, rev 2
        local binding:  label: 16
  lib entry: 1.1.1.3/32, rev 4
        local binding:  label: imp-null
  lib entry: 10.10.10.1/32, rev 18
        local binding:  label: 19
        remote binding: lsr: 10.10.10.1:0, label: imp-null
        remote binding: lsr: 10.10.10.2:0, label: 17
  lib entry: 10.10.10.2/32, rev 6
        local binding:  label: 17
        remote binding: lsr: 10.10.10.2:0, label: imp-null
        remote binding: lsr: 10.10.10.1:0, label: 17
  lib entry: 10.10.10.3/32, rev 8
        local binding:  label: imp-null
        remote binding: lsr: 10.10.10.2:0, label: 16
        remote binding: lsr: 10.10.10.1:0, label: 16


-  Forwardig table and bindings on R2 will be as below


R2#sh mpls forwarding-table 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         Pop Label  10.10.10.3/32    0             Te4/1      66.66.66.2  
17         19         10.10.10.1/32    0             Te4/1      66.66.66.2  
18         18         1.1.1.1/32       0             Te4/1      66.66.66.2      <<<<<<<
19         Pop Label  1.1.1.3/32       0             Te4/1      66.66.66.2  
20         Pop Label  55.55.55.0/24    0             Te4/1      66.66.66.2  
R2#sh mpls ldp bin
R2#sh mpls ldp bindings 
  lib entry: 1.1.1.1/32, rev 43
        local binding:  label: 18
        remote binding: lsr: 10.10.10.3:0, label: 18  <<<<<<<<
  lib entry: 1.1.1.2/32, rev 44
        local binding:  label: imp-null
        remote binding: lsr: 10.10.10.3:0, label: 16
  lib entry: 1.1.1.3/32, rev 45
        local binding:  label: 19
        remote binding: lsr: 10.10.10.3:0, label: imp-null
  lib entry: 10.10.10.1/32, rev 40
        local binding:  label: 17
        remote binding: lsr: 10.10.10.3:0, label: 19
  lib entry: 10.10.10.2/32, rev 41
        local binding:  label: imp-null
        remote binding: lsr: 10.10.10.3:0, label: 17
  lib entry: 10.10.10.3/32, rev 42
        local binding:  label: 16
        remote binding: lsr: 10.10.10.3:0, label: imp-null
R2#


- NOw applied below config on R3 with debug mpls ldp advertisement and debug mpls ldp bindings on R3 and R2

mpls ldp label
no allocate global prefix-list CCS-LOOPBACKS-PFX
mpls ldp advertise-labels 
no mpls ldp advertise-labels for CCS-LOOPBACKS


- R3 outptus after changes 

R3(config)#
*Jul 18 13:34:19.099: LDP LLAF: Enqueued work item to walk tib for default
*Jul 18 13:34:19.099: LDP LLAF: default, prev ctx flags 0x630, prev ctx prefix list None
*Jul 18 13:34:19.099: LDP LLAF: default, cur ctx flag 0x1630, cur ctx prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:19.099: LDP LLAF: default, cur global flag 0x100, cur global prefix list None
*Jul 18 13:34:19.099: LDP LLAF: No walk for default, previously default or host-route to host-route filtering
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 1.1.1.1/32, label 18 (#19)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 1.1.1.2/32, label 16 (#20)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 1.1.1.3/32, label 3 (imp-null) (#21)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 55.55.55.0/24, label 3 (imp-null) (#25)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 66.66.66.0/24, label 3 (imp-null) (#26)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.2:0 (pp 0x4A92A710): withdraw 88.88.88.88/32, label 3 (imp-null) (#27)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 1.1.1.1/32, label 18 (#19)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 1.1.1.2/32, label 16 (#20)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 1.1.1.3/32, label 3 (imp-null) (#21)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 55.55.55.0/24, label 3 (imp-null) (#25)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 66.66.66.0/24, label 3 (imp-null) (#26)
*Jul 18 13:34:20.811: tagcon: peer 10.10.10.1:0 (pp 0x46F30A70): withdraw 88.88.88.88/32, label 3 (imp-null) (#27)
*Jul 18 13:34:20.811: LDP LLAF: 1.1.1.1 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 1.1.1.1
*Jul 18 13:34:20.811: LDP LLAF: 1.1.1.2 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 1.1.1.2
*Jul 18 13:34:20.811: LDP LLAF: 1.1.1.3 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 1.1.1.3
*Jul 18 13:34:20.811: LDP LLAF: 10.10.10.1 accepted, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: 10.10.10.2 accepted, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: 10.10.10.3 accepted, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: 55.55.55.0 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 55.55.55.0
*Jul 18 13:34:20.811: LDP LLAF: 66.66.66.0 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 66.66.66.0
*Jul 18 13:34:20.811: LDP LLAF: 88.88.88.88 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 13:34:20.811: LDP LLAF: Withdraw local label for 88.88.88.88 
R3(config)#


R3#sh mpls forwarding-table 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         No Label   1.1.1.2/32       1806          Te3/1      66.66.66.1  
17         Pop Label  10.10.10.2/32    0             Te3/1      66.66.66.1  
18         No Label   1.1.1.1/32       1806          Te3/2      55.55.55.1    <<<<<<<<
19         Pop Label  10.10.10.1/32    0             Te3/2      55.55.55.1  
R3#sh mpls ldp bin          
R3#sh mpls ldp bindings 
  lib entry: 1.1.1.1/32, rev 31
        local binding:  label: 18   <<<<<<<<<
  lib entry: 1.1.1.2/32, rev 32
        local binding:  label: 16
  lib entry: 1.1.1.3/32, rev 33
        local binding:  label: imp-null
  lib entry: 10.10.10.1/32, rev 28
        local binding:  label: 19
        remote binding: lsr: 10.10.10.1:0, label: imp-null
        remote binding: lsr: 10.10.10.2:0, label: 17
  lib entry: 10.10.10.2/32, rev 29
        local binding:  label: 17
        remote binding: lsr: 10.10.10.2:0, label: imp-null
        remote binding: lsr: 10.10.10.1:0, label: 17
  lib entry: 10.10.10.3/32, rev 30
        local binding:  label: imp-null
        remote binding: lsr: 10.10.10.2:0, label: 16
        remote binding: lsr: 10.10.10.1:0, label: 16

- Outputs from R2

R2#
*Jul 18 18:02:09.287: tagcon: tibent(1.1.1.1/32): label 18 from 10.10.10.3:0 removed
*Jul 18 18:02:09.287: tib: prefix recurs walk start: 1.1.1.1/32, tableid: 0
*Jul 18 18:02:09.287: tib: get path labels: 1.1.1.1/32(0), nh tableid: 0, Te4/1, nh 66.66.66.2
*Jul 18 18:02:09.287: LDP LLAF: 1.1.1.1 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 18:02:09.287: tib: prefix walking remove route info for 1.1.1.1/32(0, 66.66.66.2, Te4/1), remote label Unknown
*Jul 18 18:02:09.291: tagcon: tibent(1.1.1.2/32): label 16 from 10.10.10.3:0 removed
*Jul 18 18:02:09.291: tagcon: tibent(1.1.1.3/32): label imp-null from 10.10.10.3:0 removed
*Jul 18 18:02:09.291: tib: prefix recurs walk start: 1.1.1.3/32, tableid: 0
*Jul 18 18:02:09.291: tib: get path labels: 1.1.1.3/32(0), nh tableid: 0, Te4/1, nh 66.66.66.2
*Jul 18 18:02:09.291: LDP LLAF: 1.1.1.3 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 18:02:09.291: tib: prefix walking remove route info for 1.1.1.3/32(0, 66.66.66.2, Te4/1), remote label Unknown
*Jul 18 18:02:09.291: tagcon: tibent(55.55.55.0/24): label imp-null from 10.10.10.3:0 removed
*Jul 18 18:02:09.291: tib: prefix recurs walk start: 55.55.55.0/24, tableid: 0
*Jul 18 18:02:09.291: tib: get path labels: 55.55.55.0/24(0), nh tableid: 0, Te4/1, nh 66.66.66.2
*Jul 18 18:02:09.291: LDP LLAF: 55.55.55.0 rejected, prefix list CCS-LOOPBACKS-PFX
*Jul 18 18:02:09.291: tib: prefix walking remove route info for 55.55.55.0/24(0, 66.66.66.2, Te4/1), remote label Unknown
*Jul 18 18:02:09.291: tagcon: tibent(66.66.66.0/24): label imp-null from 10.10.10.3:0 removed
*Jul 18 18:02:09.291: tagcon: tibent(88.88.88.88/32): label imp-null from 10.10.10.3:0 removed
R2#sh mpls forwarding-table 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         Pop Label  10.10.10.3/32    0             Te4/1      66.66.66.2  
17         19         10.10.10.1/32    0             Te4/1      66.66.66.2  
18         18         1.1.1.1/32       0             Te4/1      66.66.66.2  
19         Pop Label  1.1.1.3/32       0             Te4/1      66.66.66.2  
20         Pop Label  55.55.55.0/24    0             Te4/1      66.66.66.2  
R2#
R2#sh mpls forwarding-table 
Local      Outgoing   Prefix           Bytes Label   Outgoing   Next Hop    
Label      Label      or Tunnel Id     Switched      interface              
16         Pop Label  10.10.10.3/32    0             Te4/1      66.66.66.2  
17         19         10.10.10.1/32    0             Te4/1      66.66.66.2  
18         18         1.1.1.1/32       0             Te4/1      66.66.66.2      <<<<<<<< 
19         Pop Label  1.1.1.3/32       0             Te4/1      66.66.66.2  
20         Pop Label  55.55.55.0/24    0             Te4/1      66.66.66.2  
R2#sh mpls ldp bin
R2#sh mpls ldp bindings 
  lib entry: 1.1.1.1/32, rev 43 
        local binding:  label: 18
  lib entry: 1.1.1.2/32, rev 44
        local binding:  label: imp-null
  lib entry: 1.1.1.3/32, rev 45
        local binding:  label: 19
  lib entry: 10.10.10.1/32, rev 40
        local binding:  label: 17
        remote binding: lsr: 10.10.10.3:0, label: 19
  lib entry: 10.10.10.2/32, rev 41
        local binding:  label: imp-null
        remote binding: lsr: 10.10.10.3:0, label: 17
  lib entry: 10.10.10.3/32, rev 42
        local binding:  label: 16
        remote binding: lsr: 10.10.10.3:0, label: imp-null
  lib entry: 55.55.55.0/24, rev 46
        local binding:  label: 20
  lib entry: 66.66.66.0/24, rev 47
        local binding:  label: imp-null
  lib entry: 88.88.88.88/32, rev 48
        local binding:  label: imp-null


- After about 30mins below message is seen on R3 

 %TIB-5-WDRAWTAG: 1.1.1.1/32, tag 18; Withdrawn tag record has timed out.
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