Configuring a bypass tunnel on the PLR
Overview
To configure FRR, you must configure bypass tunnels for primary CRLSPs on the PLR by using the following methods:
Manually configuring a bypass tunnel on the PLR—Create an MPLS TE tunnel on the PLR, and configure the tunnel as a bypass tunnel for a primary CRLSP. You need to specify the bandwidth and CT that the bypass tunnel can protect, and bind the bypass tunnel to the output interface of the primary CRLSP.
You can configure a maximum of three bypass tunnels for a primary CRLSP.
Configuring the PLR to set up bypass tunnels automatically—Configure the automatic bypass tunnel setup feature (also referred to as the auto FRR feature) on the PLR. The PLR automatically sets up two bypass tunnels for each of its primary CRLSPs: one in link protection mode and the other in node protection mode. Automatically created bypass tunnels can be used to protect any type of CT, but they cannot provide bandwidth protection.
A primary tunnel can have both manually configured and automatically created bypass tunnels. The PLR will select one bypass tunnel to protect the primary CRLSP. The selected bypass tunnel is bound to the primary CRLSP.
Manually created bypass tunnels take precedence over automatically created bypass tunnels. An automatically created bypass tunnel in node protection mode takes precedence over an automatically created bypass tunnel in link protection mode. Among manually created bypass tunnels, the PLR selects the bypass tunnel for protecting the primary CRLSP by following these rules:
Selects a bypass tunnel according to the principles, as shown in Table 2.
Prefers the bypass tunnel in node protection mode over the one in link protection mode.
Prefers the bypass tunnel with a smaller ID over the one with a bigger tunnel ID.
Table 2: FRR protection principles
Bandwidth required by primary CRLSP | Primary CRLSP requires bandwidth protection or not | Bypass tunnel providing bandwidth protection | Bypass tunnel providing no bandwidth protection |
|---|---|---|---|
0 | Yes | The primary CRLSP cannot be bound to the bypass tunnel. | The primary CRLSP can be bound to the bypass tunnel if CT 0 or no CT is specified for the bypass tunnel. After binding, the RRO message does not carry the bandwidth protection flag. The bypass tunnel does not provide bandwidth protection for the primary CRLSP, and performs best-effort forwarding for traffic of the primary CRLSP. |
No | |||
None-zero | Yes | The primary CRLSP can be bound to the bypass tunnel when all the following conditions are met:
After binding, the RRO message carries the bandwidth protection flag, and the bypass tunnel provides bandwidth protection for the primary CRLSP. The primary CRLSP prefers bypass tunnels that provide bandwidth protection over those providing no bandwidth protection. | The primary CRLSP can be bound to the bypass tunnel when one of the following conditions is met:
After binding, the RRO message does not carry the bandwidth protection flag. This bypass tunnel is selected only when no bypass tunnel that provides bandwidth protection can be bound to the primary CRLSP. |
Non-zero | No | The primary CRLSP can be bound to the bypass tunnel when all the following conditions are met:
After binding, the RRO message carries the bandwidth protection flag. This bypass tunnel is selected only when no bypass tunnel that does not provide bandwidth protection can be bound to the primary CRLSP. | The primary CRLSP can be bound to the bypass tunnel when one of the following conditions is met:
After binding, the RRO message does not carry the bandwidth protection flag. The primary CRLSP prefers bypass tunnels that does not provide bandwidth protection over those providing bandwidth protection. |
Configuration restrictions and guidelines
When you configure a bypass tunnel on the PLR, follow these restrictions and guidelines:
Use bypass tunnels to protect only critical interfaces or links when bandwidth is insufficient. Bypass tunnels are pre-established and require extra bandwidth.
Make sure the bandwidth assigned to the bypass tunnel is no less than the total bandwidth needed by all primary CRLSPs to be protected by the bypass tunnel. Otherwise, some primary CRLSPs might not be protected by the bypass tunnel.
A bypass tunnel typically does not forward data when the primary CRLSP operates correctly. For a bypass tunnel to also forward data during tunnel protection, you must assign adequate bandwidth to the bypass tunnel.
A bypass tunnel cannot be used for services such as VPN.
You cannot configure FRR for a bypass tunnel. A bypass tunnel cannot act as a primary CRLSP.
Make sure the protected node or interface is not on the bypass tunnel.
After you associate a primary CRLSP that does not require bandwidth protection with a bypass tunnel that provides bandwidth protection, the primary CRLSP occupies the bandwidth that the bypass tunnel protects. The bandwidth is protected on a first-come-first-served basis. The primary CRLSP that needs bandwidth protection cannot preempt the one that does not need bandwidth protection.
After an FRR, the primary CRLSP will be down if you modify the bandwidth that the bypass tunnel can protect and your modification results in one of the following:
The CT type changes.
The bypass tunnel cannot protect adequate bandwidth as configured.
FRR protection type (whether or not to provide bandwidth protection for the primary CRLSP) changes.
Manually configuring a bypass tunnel
The bypass tunnel setup method is the same as a normal MPLS TE tunnel. This section describes only FRR-related configurations.
To configure a bypass tunnel on the PLR:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter tunnel interface view of the bypass tunnel. | interface tunnel tunnel-number [ mode mpls-te ] | N/A |
3. Specify the destination address of the bypass tunnel. | destination ip-address | The bypass tunnel destination address is the LSR ID of the MP. |
4. Configure the bandwidth and the CT to be protected by the bypass tunnel. | mpls te backup bandwidth [ ct0 | ct1 | ct2 | ct3 ] { bandwidth | un-limited } | By default, the bandwidth and the CT to be protected by the bypass tunnel are not specified. |
5. Return to system view. | quit | N/A |
6. Enter interface view of the output interface of a primary CRLSP. | interface interface-type interface-number | N/A |
7. Specify a bypass tunnel for the protected interface. | mpls te fast-reroute bypass-tunnel tunnel tunnel-number | By default, no bypass tunnel is specified for an interface. |
Automatically setting up bypass tunnels
With auto FRR, if the PLR is the penultimate node of a primary CRLSP, the PLR does not create a node-protection bypass tunnel for the primary CRLSP.
An automatically created bypass tunnel can protect multiple primary CRLSPs. A bypass tunnel is unused when the bypass tunnel is not bound to any primary CRLSP. When a bypass tunnel is unused for the period of time configured by the timers removal unused command, MPLS TE removes the bypass tunnel.
To configure auto FRR on the PLR:
Step | Command | Remarks |
|---|---|---|
1. Enter system view. | system-view | N/A |
2. Enter MPLS TE view. | mpls te | N/A |
3. Enable the auto FRR feature globally. | auto-tunnel backup | By default, the auto FRR feature is disabled globally. |
4. Specify an interface number range for the automatically created bypass tunnels. | tunnel-number min min-number max max-number | By default, no interface number range is specified, and the PLR cannot set up a bypass tunnel automatically. |
5. (Optional.) Configure the PLR to create only link-protection bypass tunnels. | nhop-only | By default, the PLR automatically creates both a link-protection and a node-protection bypass tunnel for each of its primary CRLSPs. Execution of this command deletes all existing node-protection bypass tunnels automatically created for MPLS TE auto FRR. |
6. (Optional.) Set a removal timer for unused bypass tunnels. | timers removal unused seconds | By default, a bypass tunnel is removed after it is unused for 3600 seconds. |
7. (Optional.) Return to system view. | quit | N/A |
8. (Optional.) Enter interface view. | interface interface-type interface-number | N/A |
9. (Optional.) Disable the auto FRR feature on the interface. | mpls te auto-tunnel backup disable | By default, the auto FRR feature is enabled on all RSVP-enabled interfaces after it is enabled globally. Execution of this command deletes all existing bypass tunnels automatically created on the interface for MPLS TE auto FRR. |