CCIE RS – Routing Concepts – Implement and Troubleshoot Loop Prevention Mechanisms

Implement and Troubleshoot Loop Prevention Mechanisms

Loops can occur when you are redistributing bidirectionally at 2 different points in the network

Route Tagging, Filtering

Route tagging is the process of adding an indentifier (tag) to a set of prefixes. This tag can then be called in a route map. The way I map out how to filter routes is pictured below

Screen Shot 2018-03-08 at 7.59.17 PM

Screen Shot 2018-03-08 at 8.01.55 PM

Screen Shot 2018-03-08 at 8.03.12 PM.png

Split Horizon

Split horizon is used by distance vector routing protocols. This prevents a router from sending a route back out an interface that the route was learned from. The only time you would disable this is in a hub/spoke setup where the hub would need to send routes learned back to other spokes.

Route Poisoning

Used by distance vector routing protocols. Once you learn of a route through an interface, advertise it as unreachable back through that same interface

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