Configuring a Bypass Tunnel

Context

A bypass tunnel provides protection for a link or node on a primary tunnel. An explicit path and attributes must be specified for a bypass tunnel when TE manual FRR is being configured.

Bypass tunnels are established on selected links or nodes that are not on the protected primary tunnel. If a link or node on the protected primary tunnel is used for a bypass tunnel and fails, the bypass tunnel also fails to protect the primary tunnel.

FRR does not take effect if multiple nodes or links fail simultaneously. After FRR switching is performed to switch data from the primary tunnel to a bypass tunnel, the bypass tunnel must remain Up when forwarding data. If the bypass tunnel goes Down, the protected traffic is interrupted and FRR fails. Even though the bypass tunnel goes Up again, traffic is unable to flow through the bypass tunnel but travels through the primary tunnel after the primary tunnel recovers or is reestablished.
By default, the system searches for an optimal manual FRR tunnel for each primary tunnel every 1 second and binds the bypass tunnel to the primary tunnel if there is an optimal bypass tunnel.

Perform the following configurations on the PLR.

Procedure

Run system-view
The system view is displayed.
Run interface tunnel tunnel-number
The tunnel interface view of a bypass tunnel is displayed.
Run either of the following commands to configure the IP address for the tunnel interface:
- To configure an IP address for the interface, run ip address ip-address { mask | mask-length } [ sub ]
- To configure the tunnel interface to borrow an IP address of another interface, run ip address unnumbered interface interface-type interface-number
A tunnel interface must have an IP address to forward traffic. An MPLS TE tunnel is unidirectional and does not need to configure a separate IP address for the tunnel interface. The tunnel interface usually borrows the IP address of the local loopback interface used as an LSR ID.
Run tunnel-protocol mpls te
MPLS TE is configured as a tunnel protocol.
Run destination ip-address
The LSR ID of an MP is specified as the destination address of the bypass tunnel.
Run mpls te tunnel-id tunnel-id
The tunnel ID is set for the bypass tunnel.
(Optional) Run mpls te path explicit-path path-name
An explicit path is specified for the bypass tunnel.

Before using this command, ensure that the explicit path has been created using the explicit-path command. Note that physical links of a bypass tunnel cannot overlap protected physical links of the primary tunnel.
Run mpls te bypass-tunnel
The bypass tunnel function is enabled.

After a bypass tunnel is configured, the system automatically records routes related to the bypass tunnel.
- A tunnel interface cannot be used for both a bypass tunnel and a backup tunnel. A protection failure will occur if the mpls te bypass-tunnel and mpls te backup commands are both configured on the tunnel interface.
- A tunnel interface cannot be used for both a bypass tunnel and a primary tunnel. A protection failure will occur if the mpls te bypass-tunnel and mpls te fast-reroute commands are both configured on the tunnel interface.
- A tunnel interface cannot be used for both a bypass tunnel and a protection tunnel in a tunnel protection group. A protection failure will occur if the mpls te bypass-tunnel and mpls te protection tunnel commands are both configured on the tunnel interface.
Run mpls te protected-interface interface-type interface-number
An interface to be protected by a bypass tunnel is specified.
- A bypass tunnel protects a maximum of six physical interfaces.
- A tunnel interface cannot be used for both a bypass tunnel and a backup tunnel. A protection failure will occur if the mpls te protected-interface and mpls te backup commands are both configured on the tunnel interface.
Run mpls te commit
The configuration is committed.