>I'm trying to help a client... have a 2000 server machine, trying to IP filtering... so as directed from elsewhere, I can run GPEDIT.MSC and go to the windows security policy and then into Manage IP Filters and Filter Actions. Anyhow, with so much spam and hacking coming from countries with unethical enforcement, I want to block them out... I can enter some, but then I get to an IP above the 127.0.0.0 Class A network and get a failure on the filter...
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>When I add the IP filter, I want to filter any inbound IP with the destination IP as that of the client server. I set the incoming IP address as ex:
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>222.0.0.0 with a subnet of 255.0.0.0 to block ANYTHING coming from that class A network (or obvious child therein). I get an error that
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>"This is an invalid mask for the specified IP address"
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>Any ideas???
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>Thanks

The problem is that 222.0.0.0 is NOT a class A network, but rather a class C network. Therefore, the logical subnet mask would be 255.255.255. Perhaps the security software doesn't allow "supernetting", i.e., combining classy networks into larger ones.

IP addresses that start with binary 0 are class A networks (first byte: 1-126). They are (were) assigned in chunks of 17 million addresses (first byte specified).

IP addresses that start with binary 10 are class B networks (first byte: 128-191). The are assigned in chunks of 65,000 addresses (first two bytes specified).

IP addresses that start with binary 110 are class C networks (first byte: 192-223). They are assigned in chunks of 256 addresses (first 3 bytes specified).