Cisco Cisco CRS-X Multishelf System Release Notes
cost of the links through which the tunnel passes. The headend routers recalculate the total path costs at the time of periodic path
verification. At this stage, the headend routers automatically check if the path limit is crossed and reroute the LSPs away from the
out-of-service link.
verification. At this stage, the headend routers automatically check if the path limit is crossed and reroute the LSPs away from the
out-of-service link.
This sample illustration explains the TE path cost limit application:
Figure 1: MPLS TE path cost limit application
Here, the path cost limit for the LSP is set at 50. To move the LSP away from the link between F and G, the link cost is increased to
50.
50.
The total path cost is the aggregate of individual costs assigned to the links through which the LSP traverses. The effect of specifying
a limit to the path cost (admin-weight) are:
a limit to the path cost (admin-weight) are:
• For new LSPs, if the path cost limit is crossed, the LSP is considered invalid and does not get signaled across its calculated
path. However, if an alternate path that is below the cost limit is available, then that path is signaled.
• For existing LSPs, if the path cost limit is crossed, the LSP is considered as 'failed'. If the current LSP fails (for both FRR and
non-FRR LSPs), the standby LSP will be activated if it exists. If there is no standby LSP, the tunnel will be re-optimized. If
there is no standby LSP and no path is found for a re-optimized tunnel then the tunnel is put in 'reroute pending' state and
re-optimization is attempted periodically.
there is no standby LSP and no path is found for a re-optimized tunnel then the tunnel is put in 'reroute pending' state and
re-optimization is attempted periodically.
• To recover from a cost limit failure, re-optimization will be triggered using any available path option.
MPLS TE Auto-tunnel Mesh One-hop
The MPLS TE Auto-tunnel primary one-hop feature allows automatic creation of tunnels over TE enabled interfaces to next hop
neighbors. The Auto-tunnel primary one-hop is configurable under the MPLS TE Auto-tunnel mesh group mode and for each mesh
group. The Auto-tunnel primary one-hop configuration automatically creates one-hop tunnels to next hop neighbors. A router that
becomes a next hop neighbor will have a set of one-hop tunnels created automatically.
neighbors. The Auto-tunnel primary one-hop is configurable under the MPLS TE Auto-tunnel mesh group mode and for each mesh
group. The Auto-tunnel primary one-hop configuration automatically creates one-hop tunnels to next hop neighbors. A router that
becomes a next hop neighbor will have a set of one-hop tunnels created automatically.
Soft-preemption over FRR Backup Tunnels
The soft-preemption over FRR backup tunnels feature enables to move LSP traffic over the backup tunnels when the LSP is soft-
preempted. MPLS TE tunnel soft-preemption allows removal of extra TE traffic in a graceful manner, by giving the preempted LSP
preempted. MPLS TE tunnel soft-preemption allows removal of extra TE traffic in a graceful manner, by giving the preempted LSP
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