Figure 15 Data forwarding over the TI-LFA FRR backup path
PE 1 P 1 PE 2
SRGB=[16000-17000]
SID Index=10
2168
2178
16010
IP data
16030
16010
IP data
Q space
2168
2178
P 2
SRGB=[16000-17000]
16010
SID Index=30
IP data
Extended
P space
P 3
2178
16010
IP data
P 4
SRGB=[16000-17000]
Primary path
Backup path
Failed node
Microloop avoidance after a network failure
As shown in Figure 16 , when Device B fails, traffic to Device C will be switched to the backup path
calculated by TI-LFA. After Device A finishes route convergence, traffic will be switched to the post-convergence path. If Device D and Device F have not finished route convergence and still forward traffic along the pre-convergence path, a loop is formed between Device A and Device F.
The loop exists until Device D and Device F finish route convergence.
FRR microloop avoidance and SR microloop avoidance can resolve this issue. After you configure
TI-LFA, Device A first switches traffic to the backup path calculated by TI-LFA when Device B fails.
Then, Device A waits for Device D and Device F to finish route convergence before starting route convergence. After Device A also finishes route convergence, Device A switches the traffic to the converged route.
Figure 16 Diagram for microloop avoidance after a network failure
Device A Device B Device C
Device D Device E
Device F Device G Device H
16
Pre-convergence path
Post-convergence path
Backup path
Failed node
