MPLS TE Tunnels have priority for establishing new tunnels and maintaining the current active ones. Priority and hold control these settings.
Setup and Holding Priority
- This is feature is mostly used with the MPLS-TE-Path-Bandwidth.
- There are 8 setup priorities and holding priorities, 0 to 7.
- 0 is the most preferred.
- 7 is the least preferred (default).
- Most common configuration is to set the same value for the setup and the holding priority.
- More preferred tunnel preempts less preferred tunnels.
- The setup priority is used to define preference for preempting less preferred tunnels. In other words, more preferred tunnels can push other tunnels out of the way.
- The holding priority is used to define a priority maintaining the currently established tunnel. In other words you can have a tunnel that once is establish you never want it to go down, but only establish it if there is plenty of resources. In that case you could configure setup priority 7 and holding priority 0, that way the tunnel will never get preempted once established.
- To check the current priority of a tunnel use the command show mpls traffic-eng tunnels tunnel x.
R2# sh mpls traffic-eng tunnels tunnel 36 | i [Pp]riority Bandwidth: 500 kbps (Global) Priority: 5 5 Affinity: 0x0/0xFFFF
- Most CLIs will not allow you to configure a tunnel where the holding priority is more preferred than the setup priority. This could cause a situation of a loop between two tunnels preempting each other over and over.
- Higher bandwidth tunnels should have a more preferred setup and hold priority. They might be harder to establish by passing all constraints over smaller tunnels that might have more options.
tunnel mpls traffic-eng priority
Under the interface configuration mode of a tunnel, priority setup and holding priority can be configured. If holding value is skipped, it take the setup value.
R1(config-if)# tunnel mpls traffic-eng priority (setup) [holding]