Objectives
The simulator ticks each one as soon as the network meets it.
On PE1 create segment list BOTTOM: labels 16003 (P2), 16004 (P3), 16005 (PE2).
Create policy BLUE, color 20, endpoint 5.5.5.5, with candidate preference 100 explicit segment-list BOTTOM. It comes up through P2 and P3.
Add autoroute include all: PE1’s IS-IS route to 5.5.5.5 now uses policy BLUE.
PC1 → PC2 (LAN 10, no color) now rides policy BLUE through P2 and P3.
Before you start
autoroute steers by destination, not by color: every IGP route whose path runs through the endpoint, and every BGP route whose next hop is behind it, uses the policy. The color still names the policy, but no route needs to carry it.
Concept
SR-TE policies and candidate paths
An SR-TE policy is identified by a color and an end-point. It carries a list of candidate paths with preferences. A dynamic candidate is computed on the head end over the TE database. An explicit candidate is a segment list of prefix-SIDs and adjacency-SIDs. The valid candidate with the highest preference is active.
Concept
Steering traffic into a policy: color and autoroute
Routes are steered into an SR-TE policy in two ways. With automated steering, a BGP route whose color extended community equals the policy’s color, and whose next hop equals the policy’s end-point, uses the policy. With autoroute, every IGP route through the end-point uses it, color or not. Everything else takes the default path: the SR (or LDP) shortest path.
