job screening question

William Herrin bill at
Sat Jul 7 01:45:15 UTC 2012

On Fri, Jul 6, 2012 at 8:51 PM, Ben Aitchison <ben at> wrote:
> Like when you have a /24 subnet routed to a customer, how many IP
> addresses can they use?  254?  253?  To my thinking - if it's a routed subnet that
> means the gateway is on a different address, and it'd be prudent to still have the
> double broadcast addresses.  It is also possible to utilise all 256 addresses.

There can be hidden down sides to trying that. I tried to use all 17
addresses from my Cox Business Internet /28 (the 16 in the /28 and the
"router's" external address). Rigged it as a /24 inside and used proxy
arp to move the outside addresses back out including the fake .1
default gateway that the router offered arp for but didn't hold.

Only the first 16 of the 17 addresses worked. Which 16? Why, the first
16 the cable modem saw a packet from after power-on.

Made for some interesting debugging.

Bill Herrin

William D. Herrin ................ herrin at  bill at
3005 Crane Dr. ...................... Web: <>
Falls Church, VA 22042-3004

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