Verification

The next section verifies that the desired state of the topology has been achieved.

Verify the primary path from P2 to PE5

The following output verifies that the path from P2 to PE5 is via P3.

Primary path in the RIB

Even though the P2-P3 link has a cost of 100, since there is no other route to the destination PE5, there is no backup path in the RIB, FIB, or LFIB.

Notice No FRR backup in the following output, emphasizing that there is no backup route in case the primary path fails:

RP/0/RP0/CPU0:P2#show isis fast-reroute detail 5.5.5.5/32
L2 5.5.5.5/32 [120/115] Label: 16005, medium priority
   Installed Jan 01 07:26:46.497 for 00:00:16
     via 23.0.0.3, GigabitEthernet0/0/0/0, Label: 16005, P3, SRGB Base: 16000, Weight: 0
       No FRR backup
     src PE5.00-00, 5.5.5.5, prefix-SID index 5, R:0 N:1 P:0 E:0 V:0 L:0, Alg:0
RP/0/RP0/CPU0:P2#

Notice that...