Getting a "portable" /19 or /20

Stephen Sprunk stephen at
Tue Apr 10 17:29:58 UTC 2001

Thus spake "Eric A. Hall" <ehall at>
> The example blocks/domains are useful for what they are, but their
> scope of usefulness is much smaller than real blocks/domains when
> it comes to documenting the detailed interactions between hosts and
> networks on the public Internet.

They weren't intended for that purpose.  If you need to show several
networks connected to each other, RFC1918 space should suffice for
nearly any example.  For examples demonstrating NAT, you can use
192.0.2/24 on the outside and RFC1918 on the inside.  Or, as at least
one vendor does, you can use your own IP space in your examples.

Given you only wanted a single /24 for your book (per your own
statement), it's hard to imagine that one of the above address blocks
couldn't be used.


Stephen Sprunk      "So long as they don't get violent, I want to let
CCIE #3723      everyone say what they wish, for I myself have always
K5SSS               said exactly what pleased me."  --Albert Einstein

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