The use of .0/.255 addresses.

Sun Jun 27 16:12:17 UTC 2004

On Sun, 27 Jun 2004, Peter Corlett wrote:

> 
> Stephen J. Wilcox <steve at telecomplete.co.uk> wrote:
> [...]
> > I currently have a few .255/32s with Cisco and Foundry products and
> > have various windows/linux/OSX machines that access them without
> > problems..
> 
> Well, I'd expect Linux and OSX to do the right thing. It just seems to
> be Windows that makes a complete sow's ear of it.
> 
> As to the IP addresses ending in 255 that are working from Windows
> boxes, would I be right in guessing that the first octet of the IP
> addresses in question is between 1 and 191?

Hi Peter,

actually no.. I just did a test right now, I'm at a friends and using an XP 
machine connected via a cable modem.. my results arent entirely in agreement 
with my initial post

I tested to both a "Class A" .255 we have and also to a "Class C" .255 we have

Class A: works on everything..trace, ping, ssh

Class C: spooky, traces up to the interface before the device. wont ping. 
connections fail with Network error: Cannot assign requested address. But, this 
same test works when tried from linux - possibly different behaviour between 
icmp and udp on cisco??

>From the hop-before-last (cisco 7206 12.2(14)S3) if i ping it seems to be
broadcasting out of the interface towards the .255 rather than unicasting, i
confirm this with a packet capture:

16:03:47.614187 Class-C.x.x.x > 255.255.255.255: icmp: echo request

the cisco reports correct routing of the Class-C /32 

Steve