Explains how IGP flexible algorithm computes constraint-based IPv4 and IPv6 paths so different traffic types can follow customized routes instead of the default least-cost path.
IGP flexible algorithm is a routing capability that
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lets routers calculate paths by using a defined combination of calculation type, metric type, and constraints instead of the default shortest-path calculation
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enables computation of constraint-based paths that meet specific network requirements, and
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supports path computation for both IPv4 and IPv6 destination addresses.
Operational behavior of IGP flexible algorithm
When a packet is sent to an IP address associated with a flexible algorithm, the packet follows the constraint-based path computed for that algorithm. If the destination IP address is not associated with a flexible algorithm, the packet follows the regular IGP least-cost path to the egress node.
Flexible algorithm supports various traffic management scenarios:
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Traffic segregation: Different traffic types can be forwarded over different paths.
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Performance optimization: Voice traffic can be routed over a low-latency path while other traffic uses the regular IGP path.
In IS-IS, protocol extensions support the use of flexible algorithm for IP networks.
Flexible algorithm definition
Describes how a flexible algorithm definition combines calculation type, metric type, and constraints, and explains why all participating routers must use an identical definition for consistent forwarding.
Protecting IP flexible algorithm prefixes
Explains how IP flexible algorithm traffic can be protected by Segment Routing-based TI-LFA and microloop avoidance when both IP and Segment Routing data-planes are enabled with matching participating routers.
Flexible-algorithm redistribution in IP networks
Explains how redistributed prefixes can be assigned to a specific flexible algorithm instead of algorithm 0, allowing constrained path computation and algorithm-based route matching.