Explicit Paths - Cisco ASR 9000 Series Configuration Manual

MPLS Traffic Engineering
The Loopback 0 is used as router ID.
Note

Explicit Paths

Explicit paths are used to create backup autotunnels as follows:
For NHOP Backup Autotunnels:
• NHOP excludes the protected link's local IP address.
• NHOP excludes the protected link's remote IP address.
• The explicit-path name is _autob_nhop_tunnelxxx, where xxx matches the dynamically created backup
tunnel ID.
For NNHOP Backup Autotunnels:
• NNHOP excludes the protected link's local IP address.
• NNHOP excludes the protected link's remote IP address (link address on next hop).
• NNHOP excludes the NHOP router ID of the protected primary tunnel next hop.
• The explicit-path name is _autob_nnhop_tunnelxxx, where xxx matches the dynamically created backup
tunnel ID.
Periodic Backup Promotion
The periodic backup promotion attempts to find and assign a better backup for primary tunnels that are already
protected.
With AutoTunnel Backup, the only scenario where two backups can protect the same primary tunnel is when
both an NHOP and NNHOP AutoTunnel Backups get created. The backup assignment takes place as soon as
the NHOP and NNHOP backup tunnels come up. So, there is no need to wait for the periodic promotion.
Although there is no exception for AutoTunnel Backups, periodic backup promotion has no impact on primary
tunnels protected by AutoTunnel Backup.
One exception is when a manual promotion is triggered by the user using the mpls traffic-eng fast-reroute
timers promotion command, where backup assignment or promotion is triggered on all FRR protected primary
tunnels--even unprotected ones. This may trigger the immediate creation of some AutoTunnel Backup, if the
command is entered within the time window when a required AutoTunnel Backup has not been yet created.
You can configure the periodic promotion timer using the global configuration mpls traffic-eng fast-reroute
timers promotion sec command. The range is 0 to 604800 seconds.
A value of 0 for the periodic promotion timer disables the periodic promotion.
Note
Cisco ASR 9000 Series Aggregation Services Router MPLS Configuration Guide, Release 4.3.x
120
Implementing MPLS Traffic Engineering
OL-28381-02