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Fixing a stubborn netmask setting
Authored by: denty on Jun 03, '03 06:46:20PM

A netmask like the above would tend to deny access to every other host on your local LAN - although would be very dependent upon the implementation of the IP stack.

The reason is that the netmask uses bitwise AND to determine whether an address is local or not. To use C notation, if (target_address & netmask) == (interface_address & netmask) then the address is local. Otherwise not.

Of course, that doesn't help work out why things are the way they are.



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Fixing a stubborn netmask setting
Authored by: MacMuse26 on Jun 04, '03 09:52:49PM

Most likely this is minor bug in the GUI where you set the mask.

Changing the last octect 'x.x.x.1' didn't actually result in a change behind the scenes. The code probably stopped processing when it reached the first zero in the last octet (see the binary explanation above).

By changing an earlier number in the mask (255 to 254) finally forced the entire field to be completely rewritten, and thereby fixed the problem.



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Fixing a stubborn netmask setting
Authored by: LouieNet on Jun 08, '03 03:17:39PM
I agree that it's likely a bug in the GUI. If I ever come across this again, I think I would have a look at the ifconfig -a output, and see if I can fix it there.

P.S. I'm a network engineer by trade, so imagine my surprise when I saw 255.255.255.1 for a netmask.

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G4 cube, 1152M RAM, OS X Server 10.2.6

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