Last Updated on August 1, 2021 by Admin 1
You are using an aggregate static route to null 0 to redistribute static routes into BGP.
Which problem can result if the router loses access to one of these routes?
- Black hole
- Routing loop
- Split horizon
- Unstable BGP table
If one of the aggregated routes is lost, the router will discard packets destined for that route. This condition is known as a black hole.
For example, suppose you have a number of subnets of range 126.96.36.199/16, all of which have 24 bit masks, such as 188.8.131.52/24. You aggregate them all to 184.108.40.206/16 and advertise that aggregate. If this router were to lose connectivity to one of the subnets, for example 220.127.116.11/24, then any traffic routed through this router to that subnet would never reach it, even if there were another valid path.
Split horizon is a loop avoidance mechanism that is by default always in effect, and is not affected by the loss of a subnet route that is part of an aggregate route.
BGP tables are not made unstable by the loss of the loss of a subnet route that is part of an aggregate route.
Routing loops would not occur simply from the loss of a subnet route that is part of an aggregate route.
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