Using x.x.x.0 and x.x.x.255 host addresses in supernets.

Tue Jan 8 17:23:07 UTC 2008

Jon Lewis <jlewis at lewis.org> writes:

> On Tue, 8 Jan 2008, Joe Provo wrote:
>
>>> Until you assign a .255/32 to a router loopback interface and then find
>>> that you can't get to it because some silly router between you and it
>>> thinks '.255? that's a broadcast address.'
>>
>> See the qualifier "where you don't care that broken or archaic systems
>> cannot reach them". If you have brokenness on your internal systems
>> then yes, you'd be shooting yourself in the foot.
>
> Until you shoot yourself in the foot, how would you know you have such
> brokenness on your internal systems?  That silly router happened to be
> a 7206 running (IIRC) 12.1T code.
>
> Unless you really don't care about the brokenness, or really want to
> root it all out, I'd avoid using .0 and .255 IPs.

At Inter.Net, we specifically excluded .0 and .255 from our DSL pools
so as to not screw up the day of people running outdated Windows
software any more than it was already screwed up.  At some point you
have to weigh the relative costs of 0.78% waste in IP address space
vs. technician time to troubleshoot the lossage.  With due respect to
jzp, I'll err on the side of saving myself the bucks.

                                        ---Rob