Re: The Cidr Report

[Erik Sherk <sherk () UU NET>]

> 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.