On Tue, 23 Apr 2002, Philip Hazel wrote:
> On Tue, 23 Apr 2002, Dave C. wrote:
>
> > Methinks the spec should have a very brief explanation of CIDR notation
> > for those unfamiliar with the concept
>
> The Exim 4 spec says this:
>
> . If the pattern is an IP address followed by a slash and a mask length
> (for example 10.11.42.0/24), it is matched against the IP address of the
> subject host under the given mask. The mask uses CIDR notation; it
> specifies the number of address bits that must match, starting from the
> most significant end of the address.
>
> Suggestions as to how to say that in words of fewer syllables??? :-)
Hrm.. Not necesarilly fewer syllables, but perhaps the following along
with a some examples
"the number after the slash does NOT refer to the integer number of
addresses, nor is it the high number of a range, it is a *netmask*,
specifying how many bits of the 32-bit IP address must match."
Eg:
192.168.1.5/32 (equivalent to (255.255.255.255)
matches exactly one address - 192.168.1.5
192.168.1.0/24 (equivalent to 255.255.255.0)
matches the range 192.168.1.0 thru 192.168.1.255
192.168.0.0/16 (equivalent to 255.255.0.0)
matches the range 192.168.0.0 thru 192.168.255.255
192.0.0.0/8 (equivalent to 255.0.0.0)
matches the range 192.0.0.0 thru 192.255.255.255
>
> --
> Philip Hazel University of Cambridge Computing Service,
> ph10@??? Cambridge, England. Phone: +44 1223 334714.
>
>
> --
>
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