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Example for Configuring Dynamic BFD to Detect LDP LSPs

Networking Requirements

As shown in Figure 1, the network topology is complex and unstable. PEs and P are MPLS backbone network devices, and LDP LSPs are set up on the backbone network to transmit network services.

Network services, such as VoIP, online game, and online video service, have high timeliness requirements. Data loss caused by faulty links will seriously affect services. It is required that services be fast switched to the backup LSP when the primary LSP becomes faulty, minimizing packet loss. Dynamic BFD for LDP LSPs is configured to fast detect LDP LSPs.

In this scenario, to avoid loops, ensure that all connected interfaces have STP disabled and connected interfaces are removed from VLAN 1. If STP is enabled and VLANIF interfaces of switches are used to construct a Layer 3 ring network, an interface on the network will be blocked. As a result, Layer 3 services on the network cannot run normally.

Figure 1 Networking diagram of dynamic BFD for LDP LSPs

Configuration Roadmap

The configuration roadmap is as follows:

  1. Configure OSPF between the PEs and P to implement IP connectivity on the backbone network.
  2. Configure local LDP sessions on PEs and P so that LDP LSPs can be set up to transmit network services.
  3. Configure dynamic BFD on PEs to fast detect LDP LSPs.

Procedure

  1. Create VLANs and VLANIF interfaces on the switch, configure IP addresses for the VLANIF interfaces, and add physical interfaces to the VLANs.

    # Configure PE1. The configurations of P1, P2, and PE2 are similar to the configuration of PE1, and are not mentioned here.

    <HUAWEI> system-view
[HUAWEI] sysname PE1
[PE1] interface loopback 1
[PE1-LoopBack1] ip address 1.1.1.1 32
[PE1-LoopBack1] quit
[PE1] interface gigabitethernet 0/0/1
[PE1-GigabitEthernet0/0/1] port link-type trunk
[PE1-GigabitEthernet0/0/1] port trunk allow-pass vlan 10
[PE1-GigabitEthernet0/0/1] quit
[PE1] interface gigabitethernet 0/0/2
[PE1-GigabitEthernet0/0/2] port link-type trunk
[PE1-GigabitEthernet0/0/2] port trunk allow-pass vlan 30
[PE1-GigabitEthernet0/0/2] quit
[PE1] vlan batch 10 30
[PE1] interface vlanif 10
[PE1-Vlanif10] ip address 10.1.1.1 24
[PE1-Vlanif10] quit
[PE1] interface vlanif 30
[PE1-Vlanif30] ip address 10.3.1.1 24
[PE1-Vlanif30] quit

  2. Configure OSPF to advertise the network segments connecting to interfaces on each node and to advertise the routes of hosts with LSR IDs.

    # Configure PE1. The configurations of P1, P2, and PE2 are similar to the configuration of PE1, and are not mentioned here.

    [PE1] ospf 1
[PE1-ospf-1] area 0
[PE1-ospf-1-area-0.0.0.0] network 1.1.1.1 0.0.0.0
[PE1-ospf-1-area-0.0.0.0] network 10.1.1.0 0.0.0.255
[PE1-ospf-1-area-0.0.0.0] network 10.3.1.0 0.0.0.255
[PE1-ospf-1-area-0.0.0.0] quit
[PE1-ospf-1] quit

  3. Set the cost of VLANIF 30 on PE1 to 1000. 

    [PE1] interface vlanif 30 
[PE1-Vlanif30] ospf cost 1000 
[PE1-Vlanif30] quit

    After the configuration is complete, run the display ip routing-table command on each node. You can see that the nodes learn routes from each other. The outbound interface of the route from PE1 to PE2 is VLANIF 10.

  4. Configure local LDP sessions.

    # Configure PE1. The configurations of P1, P2, and PE2 are similar to the configuration of PE1, and are not mentioned here.

    [PE1] mpls lsr-id 1.1.1.1 
[PE1] mpls 
[PE1-mpls] quit
[PE1] mpls ldp
[PE1-mpls-ldp] quit
[PE1] interface vlanif 10
[PE1-Vlanif10] mpls
[PE1-Vlanif10] mpls ldp
[PE1-Vlanif10] quit
[PE1] interface vlanif 30
[PE1-Vlanif30] mpls
[PE1-Vlanif30] mpls ldp
[PE1-Vlanif30] quit

    # Run the display mpls ldp lsp command. The command output shows that an LDP LSP destined for 4.4.4.4/32 is set up on PE1.

    [PE1] display mpls ldp lsp

 LDP LSP Information                                                            
 -------------------------------------------------------------------------------
 Flag after Out IF: (I) - LSP Is Only Iterated by RLFA
 -------------------------------------------------------------------------------
 DestAddress/Mask   In/OutLabel    UpstreamPeer    NextHop         OutInterface 
 -------------------------------------------------------------------------------
 1.1.1.1/32         3/NULL         2.2.2.2         127.0.0.1       InLoop0      
 1.1.1.1/32         3/NULL         3.3.3.3         127.0.0.1       InLoop0      
*1.1.1.1/32         Liberal/1024                   DS/2.2.2.2                   
*1.1.1.1/32         Liberal/1024                   DS/3.3.3.3                   
 2.2.2.2/32         NULL/3         -               10.1.1.2        Vlanif10     
 2.2.2.2/32         1024/3         2.2.2.2         10.1.1.2        Vlanif10     
 2.2.2.2/32         1024/3         3.3.3.3         10.1.1.2        Vlanif10     
*2.2.2.2/32         Liberal/1025                   DS/3.3.3.3                   
 3.3.3.3/32         NULL/1026      -               10.1.1.2        Vlanif10     
 3.3.3.3/32         1026/1026      2.2.2.2         10.1.1.2        Vlanif10     
 3.3.3.3/32         1026/1026      3.3.3.3         10.1.1.2        Vlanif10     
*3.3.3.3/32         Liberal/3                      DS/3.3.3.3                   
 4.4.4.4/32         NULL/1025      -               10.1.1.2        Vlanif10     
 4.4.4.4/32         1025/1025      2.2.2.2         10.1.1.2        Vlanif10     
 4.4.4.4/32         1025/1025      3.3.3.3         10.1.1.2        Vlanif10     
*4.4.4.4/32         Liberal/1026                   DS/3.3.3.3                   
 -------------------------------------------------------------------------------
 TOTAL: 11 Normal LSP(s) Found.                                                 
 TOTAL: 5 Liberal LSP(s) Found.                                                 
 TOTAL: 0 Frr LSP(s) Found.                                                     
 A '*' before an LSP means the LSP is not established                           
 A '*' before a Label means the USCB or DSCB is stale                           
 A '*' before a UpstreamPeer means the session is stale                         
 A '*' before a DS means the session is stale                                   
 A '*' before a NextHop means the LSP is FRR LSP

  5. Configure dynamic BFD to detect the connectivity of the LDP LSP between PE1 and PE2.

    # Configure an FEC list on PE1 to ensure that BFD detects only the connectivity of the LDP LSP between PE1 and PE2.

    [PE1] fec-list tortc
[PE1-fec-list-tortc] fec-node 4.4.4.4
[PE1-fec-list-tortc] quit

    # Enable BFD on PE1, specify the FEC list that triggers BFD session establishment dynamically, and adjust BFD parameters.

    [PE1] bfd
[PE1-bfd] quit
[PE1] mpls
[PE1-mpls] mpls bfd-trigger fec-list tortc
[PE1-mpls] mpls bfd enable
[PE1-mpls] mpls bfd min-tx-interval 100 min-rx-interval 100 
[PE1-mpls] quit

    # Enable BFD for LSPs passively on PE2.

    [PE2] bfd
[PE2-bfd] mpls-passive
[PE2-bfd] quit

  6. Verify the configuration.

    # Run the display bfd session all command to view the BFD session status that is created dynamically. The command output shows that the State field is displayed as Up.

    [PE1] display bfd session all
--------------------------------------------------------------------------------
Local Remote     PeerIpAddr      State     Type        InterfaceName            
--------------------------------------------------------------------------------
8192  8192       4.4.4.4         Up        D_LDP_LSP   Vlanif10                 
--------------------------------------------------------------------------------
     Total UP/DOWN Session Number : 1/0

    # Check the status of the BFD session created dynamically on PE2. The command output shows that the State field is displayed as Up.

    [PE2] display bfd session passive-dynamic
--------------------------------------------------------------------------------
Local Remote     PeerIpAddr      State     Type        InterfaceName            
--------------------------------------------------------------------------------
8192  8192       1.1.1.1         Up        E_Dynamic         -                  
--------------------------------------------------------------------------------
     Total UP/DOWN Session Number : 1/0

Configuration Files

  • PE1 configuration file

    #
sysname PE1
#
vlan batch 10 30
#
bfd
#
mpls lsr-id 1.1.1.1
mpls
 mpls bfd enable
 mpls bfd-trigger fec-list tortc
 mpls bfd min-tx-interval 100 min-rx-interval 100 
#
fec-list tortc
 fec-node 4.4.4.4
#
mpls ldp
#
interface Vlanif10
 ip address 10.1.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface Vlanif30
 ip address 10.3.1.1 255.255.255.0
 ospf cost 1000
 mpls
 mpls ldp
#
interface GigabitEthernet0/0/1
 port link-type trunk 
 port trunk allow-pass vlan 10 
#
interface GigabitEthernet0/0/2
 port link-type trunk 
 port trunk allow-pass vlan 30 
#
interface LoopBack1
 ip address 1.1.1.1 255.255.255.255
#
ospf 1
 area 0.0.0.0
  network 1.1.1.1 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.3.1.0 0.0.0.255
#
return

  • P1 configuration file

    #
sysname P1
#
vlan batch 10 20
#
mpls lsr-id 2.2.2.2
mpls
#
mpls ldp
#
interface Vlanif10
 ip address 10.1.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface Vlanif20
 ip address 10.2.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/0/1
 port link-type trunk 
 port trunk allow-pass vlan 10 
#
interface GigabitEthernet0/0/2
 port link-type trunk 
 port trunk allow-pass vlan 20 
#
interface LoopBack1
 ip address 2.2.2.2 255.255.255.255
#
ospf 1
 area 0.0.0.0
  network 2.2.2.2 0.0.0.0
  network 10.1.1.0 0.0.0.255
  network 10.2.1.0 0.0.0.255
#
return

  • P2 configuration file

    #
sysname P2
#
vlan batch 30 40
#
mpls lsr-id 3.3.3.3
mpls
#
mpls ldp
#
interface Vlanif30
 ip address 10.3.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface Vlanif40
 ip address 10.4.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/0/1
 port link-type trunk 
 port trunk allow-pass vlan 30 
#
interface GigabitEthernet0/0/2
 port link-type trunk 
 port trunk allow-pass vlan 40 
#
interface LoopBack1
 ip address 3.3.3.3 255.255.255.255
#
ospf 1
 area 0.0.0.0
  network 3.3.3.3 0.0.0.0
  network 10.3.1.0 0.0.0.255
  network 10.4.1.0 0.0.0.255
#
return

  • PE2 configuration file

    #
sysname PE2
#
vlan batch 20 40
#
bfd
 mpls-passive
#
mpls lsr-id 4.4.4.4
mpls
#
mpls ldp
#
interface Vlanif20
 ip address 10.2.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface Vlanif40
 ip address 10.4.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/0/1
 port link-type trunk 
 port trunk allow-pass vlan 20 
#
interface GigabitEthernet0/0/2
 port link-type trunk 
 port trunk allow-pass vlan 40 
#
interface LoopBack1
 ip address 4.4.4.4 255.255.255.255
#
ospf 1
 area 0.0.0.0
  network 4.4.4.4 0.0.0.0
  network 10.2.1.0 0.0.0.255
  network 10.4.1.0 0.0.0.255
#
return
Parent Topic: Configuration Examples for MPLS LDP
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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