[Cerowrt-devel] Wicked OT: 240.0.0.0/4 netblock

[Dave Taht]

On Fri, Oct 19, 2018 at 11:36 AM Rich Brown <richb.hanover at gmail.com> wrote:
>
> Sorry for distracting you from important things, but I have a question for people more knowledgeable about routing than I am...
>
> There's a person on the OpenWrt forum who is asking about using the 240.0.0.0/4 netblock for some (undefined) purpose. (If you're terminally curious, or need another reason to yell at the monitor, you could look at: https://forum.openwrt.org/t/private-network-using-240-0-0-0-4-netblock/23543/5)
>
> MY QUESTION: I have always believed that this netblock is not routable. Is this true? (A simple yes/no answer would be sufficient.)

240 is routable if you don't use a standard martians list.
http://www.radb.net/query/?keywords=fltr-martian
blocks 224/3.

It may not be routable on older versions of windows.

It may not even be assignable on some OSes and tools, currently.

It's certainly blocked on many a bogon filter and in our bcp38 package

An attempt to make "E" useful died a decade ago:
https://tools.ietf.org/html/draft-fuller-240space-02

Still, it would be a better world with 268m more routable ips in it,
wouldn't it?




> Many thanks!
>
> Rich
>
> PS I've seen the IANA advice that those addresses should not be used. (See the final note on the thread.) I'm more interested in whether it would ever work in practice: don't most upstreams block that address?
>
> PPS for all you non-Vermonters, "wicked" in this context means "extremely", often in an interesting way
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--

Dave Täht
CTO, TekLibre, LLC
http://www.teklibre.com
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