Introduction

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.

Relevant Commands

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]

Comments