Linux-Hams archive - January 1997: Re: Netmask, Broadcast etc

Re: Netmask, Broadcast etc

Terry Dawson (fefsl.bicomlkom@ahrt.hu)
Fri, 03 Jan 1997 08:20:46 +1100


Barry Winch wrote:

> Using a standard Mask of 255.255.255.0 Gives a Broadcast of
> 44.135.96.255, but does NOT allow me to connect to 44.135.96.xx
> stations outside of my LAN, so I tried a mask of 255.255.255.255,
> which now gives a broadcast of 44.135.96.125 and allows me to connect
> to systems on the LAN (once I have added them to the route file) and
> ANY system in the outside world.
>
> Is the above an acceptable approach, my main concern is that the
> Broadcast of 44.135.96.125 will limit "visibility" to 44.135.96.126
> and .127

Barry, in my home network I had my local IP address coordinator
(me in this case) allocate me a contiguous block of IP addresses
thusly:

44.136.8.96 -> 44.136.8.103

These address through the magic of binary are all identical except
the last three bits. These addresses I allocated to the hosts on
my lan. The netmask I use for the lan is 255.255.255.248 which
captures them all neatly. I use 8.96 as the network address and
8.103 as the broadcast address.

Everyone else can reach me using:

route add 44.136.8.96/29

talk to your local IP address coordinator, ask them for a
"29 bit subnet" and you should be able to do the same thing.

regards
Terry