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Re: .255 addresses still not usable after all these years?
On Fri, Jun 13, 2008 at 03:08:47PM -0400, David Hubbard wrote: > I remember back in the day of old hardware and operating > systems we'd intentionally avoid using .255 IP addresses > for anything even when the netmask on our side would have > made it fine, so I just thought I'd try it out for kicks > today. From two of four ISP's it worked fine, from Verizon > FIOS and Road Runner commercial, it didn't. So I guess > that old problem still lingers? > > David > well... .0 and .255 are still special in -some- contexts. they still form the all-zeros and all-ones broadcast addresses for the defined block... so: 192.168.16.0/23 192.168.16.0/32 is unusable 192.168.16.255/32 is useable 192.168.17.0/32 is useable 192.168.17.255/32 is unuseable. crapy CPE, vendor instruction, poor software all contribute to VLSM being poorly understood and these "gotchas" still around - years - later. my recommendation... place your caching nameservers and webservers on these addresses... if you want to force the issue. :) --bill