Mpls Point-To-Multipoint Traffic Engineering—Re-Optimizing Traffic - Cisco ASR 920 Series Configuration
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MPLS Point-to-Multipoint Traffic Engineering
MPLS Point-to-Multipoint Traffic Engineering—Re-optimizing Traffic
A P2MP TE tunnel is operational (up) when the first sub-LSP has been successfully signaled. The P2MP TE
tunnel is not operational (down) when all sub-LSPs are down. Certain events can trigger a tunnel
re-optimization:
• One of the sub-LSPs is fast-rerouted to a backup tunnel (for dynamic LSPs).
• A link is operational. (if the command is configured).
• A periodic schedule optimization occurs through the command.
• The network administrator forces a tunnel optimization through the command.
• A FRR protected interface becomes operational.
• A non-FRR LSP detects a remerge situation.
When a P2MP tunnel is reoptimized, a new LSP is signaled and traffic is moved to the new LSP.
To determine if a tunnel should be reoptimized, the router considers the following criteria:
• The router compares the number of reachable destinations between the new tree and current tree. If the
• The router verifies that the same set of reachable destinations in the current tree are also in the new tree.
• The router compares the number of destinations in the new tree with the number of destinations in the
• The router compares the metric between the current and new tree to ensure the new tree and current tree
• The router compares the administrative weights of the old tree and the new tree. The router switches to
P2MP TE uses make-before-break reoptimization, which uses the following reoptimization process:
• The new LSP is signaled.
• The headend router initiates a timer to ensure sufficient time elapses before traffic moves from the current
• Traffic is redirected from the current LSP to the new LSP.
• The timer is started for the purpose of tearing down the old sub-LSPs.
P2P TE Tunnels Coexist with P2MP TE Tunnels
Both P2P and P2MP TE tunnels share the following characteristics:
new tree contains more reachable destinations than the current tree, the router performs a reoptimization.
If the new tree contains fewer reachable destinations than the current tree, then the router keeps the
current tree.
If the new tree does not contain the same destinations, the router keeps the current tree.
old tree. If the number of destinations in the new tree is greater than the number of destinations in the
current tree, the router switches to the new tree. This guarantees that the new tree will contain all of the
existing destinations and more.
contain the same set of reachable destinations.
the new tree if the cumulative administrative weight is lower. This step applies as a tie breaker if all the
other conditions are the same.
LSP to the new LSP.
MPLS Traffic Engineering Path Calculation and Setup Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR
MPLS Point-to-Multipoint Traffic Engineering—Re-optimizing Traffic
920 Series)
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