Configuring priority for a MPLS fast reroute

These setup and hold priorities for the detour routes are available to any LSP and function the same on standard LSPs as they do on detour LSPs. The priority determines the relative importance of the detour routes during setup or preemption. The priority has two components the setup priority and the hold priority.

When a detour LSP is assigned a higher setup priority, it can preempt any LSP (detour or otherwise) that is already established and has a lower holding priority, causing resources assigned to the lower priority LSP to be diverted to the higher priority LSP. The hold priority specifies how likely an established LSP is to give up its resources to another LSP. To be preempted, an LSP must have a lower hold priority than the preempting LSPs setup priority. In addition, an established LSP can be preempted by a higher priority LSP only when it would allow the higher priority LSP to be established successfully.

To configure the detour routes of LSP frr_tunnel with a setup priority of 6 and hold priority of 1, complete the following steps.

Enable the device and configure the terminal to the global configuration mode.
```
device>enable
device# configure terminal
```
Enable the MPLS router.
```
device(config)# router mpls
```
Configure the LSP.
```
device(config-mpls)#lsp frr_tunnel
```
In this example, the name of the LSP is frr_tunnel .
Enable configuration of fast reroute options.
```
device(config-mpls-lsp-frr_tunnel)# frr
```
Configure the setup and hold priorities.
```
device(config-mpls-lsp-frr_tunnel-frr)# priority 6 1
```
Possible values for the setup and hold priorities are 0 (highest priority) through 7 (lowest priority). The setup priority must be lower than, or equal to, the configured hold priority on an LSP. By default, the setup priority is 7 and the hold priority is 0.

The following example shows the configuration of the detour routes of LSP frr_tunnel with a setup priority of 6 and hold priority of 1.

device>enable
device# configure terminal
device(config)# router mpls
device(config-mpls)#lsp frr_tunnel
device(config-mpls-lsp-frr_tunnel)# frr
device(config-mpls-lsp-frr_tunnel-frr)# priority 6 1

For additional information regarding the priority command, refer to the Fusion Command Line Interface (CLI) Reference Guide.