Profile 27 w/ Constraints

Coming from the previous lab, color the XR1-XR3 link RED. Configure the static SR Tree-SID policy to exclude RED links.

Answer

#XR1, XR3
segment-routing
 traffic-eng
  interface GigabitEthernet0/0/0/0.3013
   affinity
    name RED
   !
  !
  affinity-map
   name RED bit-position 1

#XR9
pce
 segment-routing
  traffic-eng
   affinity bit-map
    RED 1
   !
   p2mp
    policy Tree-SID-Pol1
     candidate-paths
      constraints
       affinity
        exclude
         RED

Explanation

Tree-SID allows us to use standard SR-TE tools to engineer the path an mVPN distribution tree takes. This is a big benefit over mLDP, as mLDP doesn’t give us this control.

To accomplish this lab we simply set the RED affinity on the XR1-XR3 link on both of those nodes.

The PCE must define the bit-mapping under the PCE config, and then include this as a constraint on the static Tree-SID policy.

We can see that the calculated policy now avoids XR3:

XR3 no longer has any Tree-SID state:

The multicast distribution tree is now taking this path: