Re: The Cidr Report

[Erik Sherk <]

> Tli asked:
> 
> | Exercise for the reader: If prefixes of length F and longer are filtered,
> | and a domain has a prefix of length N, how many prefixes can they propagate
> | into the backbone?  How many before people start proxy aggregating them?
> 
> A/      (2 ** F) - 1.   [assuming nobody imposes exact-match prefix filters]
> 
> B/      When we can easily do:
> 
> 	"router bgp N
>          proxy-aggregate route-map Lazy-Types

I may be misunderstanding, but does this (proposed) config statement
automaticly suppress (aggregate) any prefixes that are exactly the
same as another prefix except in the length? For example given

128.8.0.0/16
128.8.0.0/24
128.8.1.0/24

the last two would not be propogated? That would be cool!

Erik


> 
> 	! exceptions
> 	route-map Lazy-Types deny 10
>         match as-path 100
> 
> 	! the rule
> 	route-map Lazy-Types permit 20
> 	match originated-prefix-count 16"
> 	
> 	then the number 16 strikes me as a starting point,
> 	although I probably want to re-read Dennis's comments
> 	from a few years ago.
> 
> Do I pass?
> 
> 	Sean.
>