Best practice for ptp/loopback numbering for "small" enterprise multihome setup

Fri Mar 26 19:13:59 UTC 2021

On 3/26/2021 2:01 PM, William Herrin wrote:
>
> If you feel like getting fancy...
>
> Use /32 routes to reclaim the unused base and broadcast address in any /30s
>
> Pick the next largest size block that has your /24 neither at the
> start or end and assign that to your lan.
>
> Use proxy arp and more specific routes to grab traffic that doesn't
> fall in the /24 or is part of the loopback and point to point
> numbering and move it off the lan and towards its destination
> (including upstream).
>
> ..
>
> You have 10.0.1.0/24
>
> Put 10.0.0.0/22 on your LAN
> Add proxy arp and route 10.0.0.0/24 upstream
> Add proxy arp and route 10.0.2.0/23 upstream
> Add proxy arp and route 10.0.1.254/32 to your first router loopback
> etc.
>
> If you're really clever you can convince the stations that 10.0.0.1 is
> the default gateway but convince the router that 10.0.0.1 is upstream
> so that the router doesn't even need a dedicated IP address facing the
> LAN.
>
> Regards,
> Bill Herrin
>
>
And here I almost went as far as to suggest unnumbered IPs.... you're 
plan is... well... diabolical in comparison.