In the above topology, the output of "show isis segment-routing prefix" on PE11 shows the SID of PE22 is not protected.
bn303-PEa1.23:58:00(config-router-isis-af)#show isis segment-routing prefix-segments
System ID: 0000.0000.0011 Instance: 'isis-sr'
SR supported Data-plane: MPLS SR Router ID: 200.250.250.1
Node: 10 Proxy-Node: 0 Prefix: 0 Total Segments: 10
Flag Descriptions: R: Re-advertised, N: Node Segment, P: no-PHP
E: Explicit-NULL, V: Value, L: Local
Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2
Prefix SID Type Flags System ID Level Protection
------------------------- ----- ---------- ----------------------- --------------- ----- ----------
......
100.250.250.22/32 22 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0022 L2 unprotected
100.255.255.31/32 31 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0031 L2 node
The reason the SID of PE22 is "unprotected" is that the PE11 has a 2-way ECMP to the destination.
bn303-PEa1.23:58:01(config-router-isis-af)#show ip route 100.250.250.22/32
I L2 100.250.250.22/32 [115/50] via 100.2.11.0, Ethernet3/1/1
via 100.1.11.0, Ethernet10/36/1
Now let's the shutdown the interface between PE11 and P2 to break this ECMP. Now the prefix-segment is proteced now.
bn303-PEa1.00:14:21(config)#int e3/1/1
bn303-PEa1.00:14:27(config-if-Et3/1/1)#shu
bn303-PEa1.00:14:31#show ip route 100.250.250.22/32
I L2 100.250.250.22/32 [115/50] via 100.1.11.0, Ethernet10/36/1
bn303-PEa1.00:14:34#show isis segment-routing prefix-segments
Segment status codes: * - Self originated Prefix, L1 - level 1, L2 - level 2
Prefix SID Type Flags System ID Level Protection
------------------------- ----- ---------- ----------------------- --------------- ----- ----------
...
100.250.250.22/32 22 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0022 L2 node
100.255.255.31/32 31 Node R:0 N:1 P:0 E:0 V:0 L:0 0000.0000.0031 L2 node
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