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How to simplify the PIX access-list ?

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Nov 5th, 2001
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I have a question about PIX ACL. I found that there are only host objects and network objects in PIX. Therefore, if I have ten machines such as 10.1.0.1, 10.1.0.3, 10.1.0.5,...... 10.1.0.19 and each of them needs to access 100 subnets such as 10.0.1.0/24, 10.0.3.0/24, 10.0.5.0/24, ..... 10.0.199.0/24 with ten protocols such as smtp, snmp, pop3, telnet, ssh, ftp, http, https, dns, imap, do I have to make 10 x 100 x 10 = 10000 access-lists? For Checkpoint FW-1, if I group the ten machines into a group object and group the 100 subnets as another group object and group the 10 services as a group service, then I just need one rule for this. I've tried the PIX Device Manager and search thoroughly on CCO but can't find any example that can reduce the complexity of the ruleset, could you give me some hints how people configuring PIX to reduce the number of rules? Thank you very much.


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ross.filipek Tue, 11/06/2001 - 05:53
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You can take advantage of the bit-matching technique when writing your wildcard masks. For example, if your access list looks like this:


access-list 100 permit tcp 10.1.0.1 0.0.0.30 10.0.1.0 0.0.254.255 eq 23


then 10.1.0.X (where X is an odd number less than or equal to 31) will be able to telnet to 10.0.Y.0/24 (where Y is an odd number less than or equal to 253). Note that you'll be permitting more hosts and networks than those you've specified in your example, but you'll be able to write your entire access list in 13 lines (1 line per port; some ports require multiple protocols).

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