nanog mailing list archives

Re: Stupid Question maybe?


From: Owen DeLong <owen () delong com>
Date: Wed, 19 Dec 2018 12:46:43 -0800



On Dec 19, 2018, at 12:11 , Thomas Bellman <bellman () nsc liu se> wrote:

On 2018-12-19 20:47 MET, valdis.kletnieks () vt edu wrote:

There was indeed a fairly long stretch of time (until the CIDR RFC came out and
specifically said it wasn't at all canon) where we didn't have an RFC that
specifically said that netmask bits had to be contiguous.

How did routers select the best (most specific) route for an address?
If the routing table held both (e.g.) 10.20.30.0/255.255.255.64 and
10.20.30.0/255.255.255.32, then 10.20.30.97 would match both, and have
the same number of matching bits.

      /Bellman


The institution of the longest match rule came with the prohibition (deprecation) of
discontiguous net masks.

Owen


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