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Old 07-13-2002, 02:50 PM   #1
Registered: Dec 2001
Location: Beckwith Township, Ontario, Canada
Distribution: Slackware 14.0, Slackware-64 14.1
Posts: 119

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Question address match list syntax for bind

What is the proper syntax for an address match list when using a.b.c.d/xx?

In other words, what is the significance of the prefix (a.b.c.d) vs. the number after the "/"?

Old 07-14-2002, 09:23 PM   #2
Registered: Aug 2001
Location: Off the coast of Madadascar
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Wow you really made that hard to understand what your quesion was, but I think I got it.

What your referring to is the subnet mask after the IP address. The subnet mask is used to identify a network of computers.

In the most basic form there are 4 possiblele values that can be placed after the "/"

/ or /8
/ or /16
/ or /24
/ or /32

Each has its on significance in setting up IP rules. (Say in BIND configs) The first of the options means to match only the first octet of an IP address.

e.x Say IP address attempts to query your DNS server. If you told BIND to only to allow "". That machine with that IP address would certainly make it through. But if your intention as to ONLY allow that machine, you would be thoroughly disappointed. Like I said before, using the subnet mask designates IPs that match the first octet (ie 145) So an the IP address or or would all be able to query your DNS server.

Now the next subnet mask or /16 means to allow the first two octets. (ex 145.78) Then any IP address thats starts with 145.78 would get through.

If your still following me then you should be able to figure out that the next subnet mask or /24 designates the match of the first three octets (145.78.45).

And finally or /32 means to EXACTLY match an IP address. That is the best subnet mask to use if you intend to restrict to one IP address.

Old 07-16-2002, 09:08 AM   #3
Registered: Dec 2001
Location: Beckwith Township, Ontario, Canada
Distribution: Slackware 14.0, Slackware-64 14.1
Posts: 119

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Thumbs up

That's exactly what I was looking for--thanks!!!


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