Path metric may remain in the routing table after this tie-breaker is applied. Lowest-repair-path-metric-Eliminates LFAs whose metric to the protected prefix is high. Linecard-disjoint-Eliminates LFAs that share the line card with the protected path. Interface-disjoint-Eliminates LFAs that share the outgoing interface with the protected path. EIGRP uses the following four attributes to implement tie-breaking rules: A tie-breaking rule considers LFAs that satisfy certain conditions or have certain attributes. When there are multiple candidate LFAs for a given primary path, EIGRP uses a tie-breaking rule to select one LFA per primary path per prefix. Per-link computations because per-prefix computations evaluate all possible LFAs and use tie-breakers to select the best LFA Per-prefix computations provide better load sharing and better protection coverage than The per-prefix approach is preferred over the per-link approach because of its greater applicabilityĪnd better bandwidth utilization. Per-prefix (prefix-based) computation: Prefix-based LFAs allow computing backup information per prefix (network) and protect RedirectingĪll traffic to the next hop may lead to congestion on the link to the next hop Therefore, the per-link approach is suboptimal and not the best approach for capacity planningīecause all traffic from the primary link is redirected to the next hop instead of being spread over multiple paths. The per-link approach protects only the next-hop address. Repair or the Fast Reroute (FRR) ability. This means that the whole set of prefixes sharing the primary link also share the Per-link (link-based) computation: In link-based LFAs, all prefixes (networks) that are reachable through the primary (protected) Interior Gateway Protocols (IGPs) compute LFAs in the following two ways: Traffic is redirected to an LFA after a network failure and the LFA makes the forwarding decision without any knowledge of Interior Gateway Routing Protocol (EIGRP) networks, precomputed repair paths or backup routes are known as feasible successorsĪ loop-free alternate (LFA) is a precomputed next-hop route that delivers a packet to its destination without looping back. Paths in anticipation of failures so that the repair paths can be activated the moment a failure is detected. Their forwarding data and the failed link is eliminated from the routing computation. By the time the routing transition is complete, all devices in the network revise Until the routing transition is complete. These repair paths are used from the time the router detects the failure Paths for packets that would have used the failed link. A device adjacent to the failed link employs a set of repair Meanwhile, packets affectedīy the network failure need to be steered to their destinations. The propagation of this information may take several hundred milliseconds. Network are unaware of the nature and location of this failure until information about this failure is propagated through When a link or a device fails, initially only the neighboring devices are aware of the failure. Of the network, the connectivity between the source and destination pairs of devices is interrupted. Until the transition is complete and all devices are converged on a common view The time taken for thisĬomputation is called routing transition. When a link or a device fails, distributed routing algorithms compute new routes or repair paths. Feature Information for EIGRP Loop-Free Alternate Fast Reroute.Configuration Examples for EIGRP Loop-Free Alternate Fast Reroute.
EIGRP IP FAST REROUTE HOW TO
How to Configure EIGRP Loop-Free Alternate Fast Reroute.Information About EIGRP Loop-Free Alternate Fast Reroute.Restrictions for EIGRP Loop-Free Alternate Fast Reroute.This module describes how to configure the EIGRP Loop-Free Alternate Fast Rerouteįeature and enable load-sharing and tie-breaking configurations for the feasible successors or LFAs that are identified by Successors or loop-free alternates (LFAs). In EIGRP networks, precomputed backup routes or repair paths are known as feasible Fast Reroute (FRR) is the mechanism that enables traffic that traverses a failed Routes in the Routing Information Base (RIB). The routing transition time to less than 50 ms by precomputing repair paths or backup routes and installing these paths or The EIGRP Loop-Free Alternate Fast Reroute feature allows the Enhanced Interior Gateway Routing Protocol (EIGRP) to reduce
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