On Thu, Aug 30, 2012 at 11:50 AM, Blake Hudson <bl...@ispn.net> wrote: > Matt Addison wrote the following on 8/29/2012 6:08 PM: > >> Sent from my mobile device, so please excuse any horrible misspellings. >> >> On Aug 29, 2012, at 18:30, james machado <hvgeekwt...@gmail.com> wrote: >> >>> On Wed, Aug 29, 2012 at 1:55 PM, STARNES, CURTIS >>> <curtis.star...@granburyisd.org> wrote: >>>> >>>> Sorry for the top post... >>>> >>>> Not necessarily a Level 3 problem but; >>>> >>>> We are announcing our /19 network as one block via BGP through AT&T, not >>>> broken up into smaller announcements. >>>> Earlier in the year I started receiving complaints that some of our >>>> client systems were having problems connecting to different web sites. >>>> After much troubleshooting I noticed that in every instance the xlate in >>>> our Cisco ASA for the client's IP last octet was either a 0 or 255. >>>> Since I am announcing our network as a /19, the subnet mask is >>>> 255.255.224.0, that would make our network address x.x.192.0 and the >>>> broadcast x.x.223.255. >>>> So somewhere the /24 boundary addresses were being dropped. >>>> >>>> Just curious if anyone else has seen this before. >>> >>> some OS's by M and others as well as some devices have IP stacks which >>> will not send or receive unicast packets ending in 0 or 255. have had >>> casses where someone was doing subnets that included those in the DCHP >>> scopes and the computers that received these addresses were black >>> holes. >>> >>> james >> >> MSKB 281579 affects XP home and below. Good times anytime someone adds >> a .0 or .255 into an IP pool. >> > It might be relevant to note that XP and below is simply respecting classful > boundaries. This does not affect all .0 or .255 address, just class C > addresses (192.0.0.0 through 223.255.255.255) that end with .0 or .255. If > your IP range is 0.0.0.0 - 191.255.255.255 you are not affected (by this > particular bug) by using .0 or .255 as the last octet unless the address is > ALSO the last octet of the classful boundary for your subnet. In effect, > these OS's simply enforce classful boundaries regardless of the subnet mask > you have set. As the KB states, this "bug" affects supernets only. I'm not > trying to defend MS (they can do that themselves), but your statement was > misleading.
I can distinctly remember having the issue in 10/8 address space with Win2k and WinXP > > We do, sometimes, use .0 and .255 addresses. Most clients work fine with > them (including XP). However, I have personally seen a few networks where an > administrator had blocked .0 and .255 addresses, causing problems for people > on his network communicating to hosts that ended in .0 or .255. It has been > years since I have seen an issue with a .0 or a .255 IP however. Given fears > over IP shortages, even a couple percent of addresses wasted due to > subnetting can be cause for adjusting network policy. I would not be > surprised if folks who excluded .0 and .255 addresses from their assignable > pools will re-evaluate that decision over the next few years. > > --Blake > > >
