View Source: RouteAggregation - Waikato Linux Users Group

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[RouteAggregation] refers to the collection of "adjacent" routes together, in order to shorten the routing tables. It is made possible with ClasslessInterDomainRouting ([CIDR]).

If you have enough adjacent routes to use a higher prefix, you can use RouteAggregation. For example, if your network has
 192.168.0.0/24
 192.168.1.0/24
On different subnets internally, you can advertise the whole lot by using 192.168.0.0/23. A /23 prefix has one less bits than a /24, which is 2 networks - so the 2 adjacent /24 networks starting from 192.168.0.0/24 can be thought of as a single /23


Essentially any CIDR prefix can be thought of as the aggregation of all longer prefixes under it:

192.168.0.0/16 is the aggregation of the 256 192.168.x.0/24 addresses

A /24 prefix is the aggregation of the 4 /25 prefixes under it

See http://jodies.de/ipcalc for a CIDR subnet calculator

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Part of CategoryNetworking

2 pages link to RouteAggregation:

Last edited on Tuesday, August 12, 2003 12:10:30 pm by DanielLawson

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