Example for Configuring BFD to Monitor VPN Routes

This section provides an example for configuring BFD to monitor VPN routes.

Networking Requirements

As shown in Figure 1:

CE1 and CE2 belong to VPN-A and access the MPLS backbone network through PE1 and PE2, respectively.
GE 0/1/0 of PE1 and GE 0/1/0 of PE2 are bound to VPN-A.
BFD in asynchronous mode is used to monitor the VPN route between PE1 and PE2.

Figure 1 BFD for VPN routes

Interfaces 1 and 2 in this example represent GE 0/1/0 and GE 0/1/8, respectively.

Configuration Roadmap

The configuration roadmap is as follows:

Configure a BFD session on PE1 to monitor the multi-hop path from PE1 to PE2.
Configure a BFD session on PE2 to monitor the multi-hop path from PE2 to PE1.

Data Preparation

To complete the configuration, you need the following data:

Peer IP address monitored by BFD
BFD session names
Local and remote discriminators of BFD sessions

Procedure

Assign an IP address to each interface. For configuration details, see Configuration Files in this section.
Configure the MPLS backbone network to interconnect PE1 and PE2. For configuration details, see Configuration Files in this section.
Configure a VPN instance. For configuration details, see Configuration Files in this section.

Configure the route between PE1 and PE2 to be reachable. For configuration details, see Configuration Files in this section.

After the configurations are complete, PE1 can ping the IP address of GE 0/1/0 on PE2.

<PE1> ping -vpn-instance vpna 10.2.1.2
  PING 10.2.1.2: 56  data bytes, press CTRL_C to break
    Reply from 10.2.1.2: bytes=56 Sequence=1 ttl=254 time=60 ms
    Reply from 10.2.1.2: bytes=56 Sequence=2 ttl=254 time=50 ms
    Reply from 10.2.1.2: bytes=56 Sequence=3 ttl=254 time=50 ms
    Reply from 10.2.1.2: bytes=56 Sequence=4 ttl=254 time=60 ms
    Reply from 10.2.1.2: bytes=56 Sequence=5 ttl=254 time=50 ms
  --- 10.2.1.2 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 50/54/60 ms

Configure BFD to monitor the VPN route between PE1 and PE2.

# Enable BFD on PE1, establish a BFD session with PE2, and bind the session to the VPN instance.

[~PE1] bfd
[*PE1-bfd] quit
[*PE1] bfd 1to2_vpn bind peer-ip 10.2.1.2 vpn-instance vpna
[*PE1-bfd-session-1to2_vpn] discriminator local 12
[*PE1-bfd-session-1to2_vpn] discriminator remote 21
[*PE1-bfd-session-1to2_vpn] commit
[~PE1-bfd-session-1to2_vpn] quit

# Enable BFD on PE2, establish a BFD session with PE1, and bind the session to the VPN instance.

[~PE2] bfd
[*PE2-bfd] quit
[*PE2] bfd 2to1_vpn bind peer-ip 10.1.1.2 vpn-instance vpna
[*PE2-bfd-session-2to1_vpn] discriminator local 21
[*PE2-bfd-session-2to1_vpn] discriminator remote 12
[*PE2-bfd-session-2to1_vpn] commit
[~PE2-bfd-session-2to1_vpn] quit

Verify the configuration.

After completing the configurations, run the display bfd session peer-ip vpn-instance vpn-name verbose command on PE1 and PE2. The command output shows that a multi-hop BFD session has been established and its status is Up.

The following example uses the command output on PE1.

<PE1> display bfd session peer-ip 10.2.1.2 vpn-instance vpna verbose
(w): State in WTR 
(*): State is invalid
--------------------------------------------------------------------------------
(Multi Hop) State : Up                        Name : 1to2_vpn
------------------------------------------------------------------------------
  Local Discriminator    : 12              Remote Discriminator   : 21
  Session Detect Mode    : Asynchronous Mode Without Echo Function
  BFD Bind Type          : Peer Ip Address
  Bind Session Type      : Static
  Bind Peer IP Address   : 10.2.1.2
  Bind Interface         : -
  Vpn Instance Name      : vpna
  FSM Board Id           : 1                TOS-EXP                : 7
  Min Tx Interval (ms)   : 10               Min Rx Interval (ms)   : 10
  Actual Tx Interval (ms): 10               Actual Rx Interval (ms): 10
  Local Detect Multi     : 3                Detect Interval (ms)   : 30
  Echo Passive           : Disable          Acl Number             : -
  Destination Port       : 4784             TTL                    : 255  
  Proc Interface Status  : Disable          Process PST            : Disable
  WTR Interval (ms)      : -                Config PST             : Disable
  Active Multi           : 3
  Last Local Diagnostic  : No Diagnostic
  Bind Application       : No Application Bind
  Session TX TmrID       : -                Session Detect TmrID   : -
  Session Init TmrID     : -                Session WTR TmrID      : -
  PDT Index              : FSM-0|RCV-0|IF-0|TOKEN-0
  Session Description    : -
------------------------------------------------------------------------------
     Total UP/DOWN Session Number : 1/0

Configuration Files

PE1 configuration file

#
 sysname PE1
#
ip vpn-instance vpna
 route-distinguisher 100:1
 apply-label per-instance
 vpn-target 111:1 export-extcommunity
 vpn-target 111:1 import-extcommunity
#
 bfd
#
 mpls lsr-id 1.1.1.1
 mpls
#
mpls ldp
#
interface gigabitethernet0/1/0
 undo shutdown
 ip binding vpn-instance vpna
 ip address 10.1.1.2 255.255.255.0
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 172.16.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface LoopBack1
 ip address 1.1.1.1 255.255.255.255
#
bgp 100
 peer 3.3.3.3 as-number 100
 peer 3.3.3.3 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  peer 3.3.3.3 enable
 #
 ipv4-family vpnv4
  policy vpn-target
  peer 3.3.3.3 enable
 #
 ipv4-family vpn-instance vpna
  peer 10.1.1.1 as-number 65410
  import-route direct
#
ospf 100
area 0.0.0.0
  network 1.1.1.1 0.0.0.0
  network 172.16.1.0 0.0.0.255
#
bfd 1to2_vpn bind peer-ip 10.2.1.2 vpn-instance vpna
 discriminator local 12
 discriminator remote 21
return

PE2 configuration file

#
sysname PE2
#
ip vpn-instance vpna
 route-distinguisher 200:1
 apply-label per-instance
 vpn-target 111:1 export-extcommunity
 vpn-target 111:1 import-extcommunity
#
 bfd
#
 mpls lsr-id 3.3.3.3
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 172.16.2.2 255.255.255.0
 mpls
 mpls ldp
#
interface gigabitethernet0/1/0
 undo shutdown
 ip binding vpn-instance vpna
 ip address 10.2.1.2 255.255.255.0
#
interface LoopBack1
 ip address 3.3.3.3 255.255.255.255
#
bgp 100
 peer 1.1.1.1 as-number 100
 peer 1.1.1.1 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  peer 1.1.1.1 enable
 #
 ipv4-family vpnv4
  policy vpn-target
  peer 1.1.1.1 enable
 #
 ipv4-family vpn-instance vpna
  peer 10.2.1.1 as-number 65420
  import-route direct
#
ospf 100
 area 0.0.0.0
  network 3.3.3.3 0.0.0.0
  network 172.16.2.0 0.0.0.255
#
bfd 2to1_vpn bind peer-ip 10.1.1.2 vpn-instance vpna
 discriminator local 21
 discriminator remote 12
return

P configuration file

#
sysname P
#
 mpls lsr-id 2.2.2.2
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 172.16.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 172.16.2.1 255.255.255.0
 mpls
 mpls ldp
#
interface LoopBack1
  ip address 2.2.2.2 255.255.255.255
#
ospf 100
 area 0.0.0.0
  network 172.16.1.0 0.0.0.255
  network 172.16.2.0 0.0.0.255
  network 2.2.2.2 0.0.0.0
return

CE1 configuration file

#
 sysname CE1
#
interface gigabitethernet0/1/0
 undo shutdown
ip address 10.1.1.1 255.255.255.0
#
bgp 65410
 peer 10.1.1.2 as-number 100
 #
 ipv4-family unicast
  import-route direct
  peer 10.1.1.2 enable
return

CE2 configuration file

#
 sysname CE2
#
interface gigabitethernet0/1/0
 undo shutdown
 ip address 10.2.1.1 255.255.255.0
#
bgp 65420
 peer 10.2.1.2 as-number 100
 #
 ipv4-family unicast
  import-route direct
  peer 10.2.1.2 enable
return