Re: The Cidr Report

["Sean M. Doran" <smd () clock org>]

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

        ! 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.