What’s the difference between an Aggregate and a Generate route in Junos?

22 02 2012

Finally I have got this clear in my head, thanks to this nice piece of explanation.

Aggregate routes are quite like generate routes in that they become active when a contributing route is present from a peer or neighbour.  What’s different is that the aggregate route always has a discard or reject, so isn’t used to forward traffic.  A generate route has a preferred contributing route, and this is used to forward the traffic even in the event that there isn’t a contributing route matching the packet’s destination.

In real-world usage, aggregates are used by people to summarise their address space into a single block to keep the Internet routing table smaller.   Generate routes are usually used at the edge of a network to generate a conditional default route into the IGP if there are any routes received from the upstream ISP.

 

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2 responses

7 01 2014
Robert Juric (@robertjuric)

Best explanation I’ve seen yet! Quite simple, but when you give those examples, it finally made sense in my head.Thanks!

3 03 2014
DataPlumber

Thanks – that’s nice to hear!

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