Example for Configuring Dynamic BFD for CR-LSPs
Networking Requirements
The path of the primary CR-LSP is LSRA -> LSRB -> LSRC.
The path of the backup CR-LSP is LSRA -> LSRD -> LSRC.
When the primary CR-LSP fails, traffic switches to the backup CR-LSP. After the primary CR-LSP recovers, traffic switches back to the primary CR-LSP in 15 seconds. If both the primary CR-LSP and backup CR-LSP fail, traffic switches to the best-effort path. Explicit paths can be configured for the primary and backup CR-LSPs. A best-effort path can be generated automatically. In this example, the best-effort path is LSRA -> LSRD -> LSRB -> LSRC. The calculated best-effort path varies according to the faulty node.
Dynamic BFD for CR-LSPs needs to be configured to detect primary and backup CR-LSPs:
When the primary CR-LSP fails, traffic fast switches to the backup CR-LSP.
When the backup CR-LSP fails within 15 seconds after the primary CR-LSP recovers, traffic switches back to the primary CR-LSP.
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.
Compared with static BFD, dynamic BFD is much easier to configure. In addition, dynamic BFD can reduce the number of BFD sessions, and use less network resources because only one BFD session can be created on a tunnel interface.
Configuration Roadmap
The configuration roadmap is as follows:
Configure a hot-standby CR-LSP and best-effort path.
Enable BFD on the ingress node, configure dynamic BFD for CR-LSPs, and set the intervals for sending and receiving BFD packets and local BFD detection multiplier.
Enable the capability to passively create BFD sessions on the egress node.
Procedure
- Configure a hot-standby CR-LSP and best-effort path.
Configure the primary CR-LSP, backup CR-LSP, and best-effort path according to Example for Configuring CR-LSP Hot Standby.
- Configure dynamic BFD for CR-LSPs on the ingress node.
Configure dynamic BFD for CR-LSPs, and set the intervals for sending and receiving BFD packets to 500 ms and local BFD detection multiplier to 3.
# Configure LSRA.
[LSRA] bfd [LSRA-bfd] quit [LSRA] interface tunnel 1 [LSRA-Tunnel1] mpls te bfd enable [LSRA-Tunnel1] mpls te bfd min-tx-interval 500 min-rx-interval 500 detect-multiplier 3 [LSRA-Tunnel1] mpls te commit
- Enable the capability to passively create BFD sessions on the egress node.
# Configure LSRC.
[LSRC] bfd [LSRC-bfd] mpls-passive [LSRC-bfd] quit
After the configurations are complete, run the display bfd session mpls-te interface Tunnel 1 te-lsp command on LSRA. You can see that the BFD session status is Up.
[LSRA] display bfd session mpls-te interface Tunnel 1 te-lsp -------------------------------------------------------------------------------- Local Remote PeerIpAddr State Type InterfaceName -------------------------------------------------------------------------------- 8192 8192 3.3.3.9 Up D_TE_LSP Tunnel1 -------------------------------------------------------------------------------- Total UP/DOWN Session Number : 1/0
Run the display bfd session passive-dynamic command on LSRC. You can see that a BFD session is created passively.
[LSRC] display bfd session passive-dynamic -------------------------------------------------------------------------------- Local Remote PeerIpAddr State Type InterfaceName -------------------------------------------------------------------------------- 8192 8192 1.1.1.9 Up E_Dynamic - -------------------------------------------------------------------------------- Total UP/DOWN Session Number : 1/0 - Verify the configuration.
Connect two interfaces, Port 1 and Port 2, on a tester to LSRA and LSRC respectively. On Port 1, inject MPLS traffic and send traffic to Port 2. After the cable attached to GE0/0/1 on LSRA or LSRB is removed, traffic fast switches to the backup CR-LSP at the millisecond level.
After the cable is inserted into GE0/0/1, run the display mpls te tunnel-interface tunnel 1 command to view tunnel information until the primary CR-LSP is set up. Then remove the cable from GE0/0/2 on LSRA or LSRD within 15s. You can see that traffic switches back to the primary CR-LSP at the millisecond level.
Configuration Files
LSRA configuration file
# sysname LSRA # vlan batch 100 500 # bfd # mpls lsr-id 1.1.1.9 mpls mpls te mpls rsvp-te mpls te cspf # explicit-path backup-path next hop 172.5.1.2 next hop 172.3.1.1 next hop 3.3.3.9 # explicit-path pri-path next hop 172.1.1.2 next hop 172.2.1.2 next hop 3.3.3.9 # interface Vlanif100 ip address 172.1.1.1 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif500 ip address 172.5.1.1 255.255.255.0 mpls mpls te mpls rsvp-te # interface GigabitEthernet0/0/1 port link-type trunk port trunk allow-pass vlan 100 # interface GigabitEthernet0/0/2 port link-type trunk port trunk allow-pass vlan 500 # interface LoopBack1 ip address 1.1.1.9 255.255.255.255 # interface Tunnel1 ip address unnumbered interface LoopBack1 tunnel-protocol mpls te destination 3.3.3.9 mpls te tunnel-id 100 mpls te bfd enable mpls te bfd min-tx-interval 500 min-rx-interval 500 mpls te record-route mpls te path explicit-path pri-path mpls te path explicit-path backup-path secondary mpls te backup hot-standby mode revertive wtr 15 mpls te backup ordinary best-effort mpls te commit # ospf 1 opaque-capability enable area 0.0.0.0 network 1.1.1.9 0.0.0.0 network 172.1.1.0 0.0.0.255 network 172.5.1.0 0.0.0.255 mpls-te enable # return
LSRB configuration file
# sysname LSRB # vlan batch 100 200 400 # mpls lsr-id 2.2.2.9 mpls mpls te mpls rsvp-te # interface Vlanif100 ip address 172.1.1.2 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif200 ip address 172.2.1.1 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif400 ip address 172.4.1.1 255.255.255.0 mpls mpls te mpls rsvp-te # interface GigabitEthernet0/0/1 port link-type trunk port trunk allow-pass vlan 100 # interface GigabitEthernet0/0/2 port link-type trunk port trunk allow-pass vlan 200 # interface GigabitEthernet0/0/3 port link-type trunk port trunk allow-pass vlan 400 # interface LoopBack1 ip address 2.2.2.9 255.255.255.255 # ospf 1 opaque-capability enable area 0.0.0.0 network 2.2.2.9 0.0.0.0 network 172.1.1.0 0.0.0.255 network 172.2.1.0 0.0.0.255 network 172.4.1.0 0.0.0.255 mpls-te enable # return
LSRC configuration file
# sysname LSRC # vlan batch 200 300 # bfd mpls-passive # mpls lsr-id 3.3.3.9 mpls mpls te mpls rsvp-te # interface Vlanif200 ip address 172.2.1.2 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif300 ip address 172.3.1.1 255.255.255.0 mpls mpls te mpls rsvp-te # interface GigabitEthernet0/0/1 port link-type trunk port trunk allow-pass vlan 300 # interface GigabitEthernet0/0/2 port link-type trunk port trunk allow-pass vlan 200 # interface LoopBack1 ip address 3.3.3.9 255.255.255.255 # ospf 1 opaque-capability enable area 0.0.0.0 network 3.3.3.9 0.0.0.0 network 172.2.1.0 0.0.0.255 network 172.3.1.0 0.0.0.255 mpls-te enable # return
LSRD configuration file
# sysname LSRD # vlan batch 300 400 500 # mpls lsr-id 4.4.4.9 mpls mpls te mpls rsvp-te # interface Vlanif300 ip address 172.3.1.2 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif400 ip address 172.4.1.2 255.255.255.0 mpls mpls te mpls rsvp-te # interface Vlanif500 ip address 172.5.1.2 255.255.255.0 mpls mpls te mpls rsvp-te # interface GigabitEthernet0/0/1 port link-type trunk port trunk allow-pass vlan 300 # interface GigabitEthernet0/0/2 port link-type trunk port trunk allow-pass vlan 500 # interface GigabitEthernet0/0/3 port link-type trunk port trunk allow-pass vlan 400 # interface LoopBack1 ip address 4.4.4.9 255.255.255.255 # ospf 1 opaque-capability enable area 0.0.0.0 network 4.4.4.9 0.0.0.0 network 172.3.1.0 0.0.0.255 network 172.4.1.0 0.0.0.255 network 172.5.1.0 0.0.0.255 mpls-te enable # return