| Copyright (c) 2008 Don R. Crawley
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| | 80 (www). In the second ACE, the same
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| Access Control Lists (ACLs) are
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| | traffic flow is permitted for destination
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| sequential lists of permit and deny
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| | port 443. Notice in the output of the
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| conditions applied to traffic flows on a
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| | show access-list that line numbers are
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| device interface. ACLs are based on
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| | displayed and the extended parameter is
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| various criteria including protocol type
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| | also included, even though neither was
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| source IP address, destination IP
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| | included in the configuration statements.
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| address, source port number, and/or
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| | You can deactivate an ACE without
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| destination port number.
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| | deleting it by appending the inactive
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| ACLs can be used to filter traffic for
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| | option to the end of the line.
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| various purposes including security,
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| | As with Cisco routers, there is an
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| monitoring, route selection, and network
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| | implicit "deny any" at the end of every
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| address translation. ACLs are comprised
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| | ACL. Any traffic that is not explicitly
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| of one or more Access Control Entries
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| | permitted is implicitly denied.
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| (ACEs). Each ACE is an individual line
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| | **Editing ACLs and ACEs**
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| within an ACL.
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| | New ACEs are appended to the end of the
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| ACLs on a Cisco ASA Security Appliance
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| | ACL. If you want, however, to insert the
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| (or a PIX firewall running software
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| | new ACE at a particular location within
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| version 7.x or later) are similar to
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| | the ACL, you can add the line number
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| those on a Cisco router, but not
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| | parameter to the ACE:asa04(config)#
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| identical. Firewalls use real subnet
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| | access-list demo1 line 1 deny tcp host
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| masks instead of the inverted mask used
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| | 10.1.0.2 any eq wwwasa04(config)# show
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| on a router. ACLs on a firewall are
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| | access-list demo1access-list demo1; 3
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| always named instead of numbered and are
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| | elementsaccess-list demo1 line 1 extended
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| assumed to be an extended list.
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| | deny tcp host 10.1.0.2 any eq
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| The syntax of an ACE is relatively
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| | wwwaccess-list demo1 line 2 extended
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| straight-forward:
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| | permit tcp 10.1.0.0 255.255.255.0 any eq
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| Ciscoasa(config)#access-list name [line
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| | wwwaccess-list demo1 line 3 extended
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| number] [extended] {permit | deny}
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| | permit tcp 10.1.0.0 255.255.255.0 any eq
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| protocol source_IP_address source_netmask
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| | https
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| [operator source_port]
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| | Notice in the first line of the example
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| destination_IP_address
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| | above that an ACE is added at line one in
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| destination_netmask [operator
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| | the ACL. Notice in the output from the
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| destination_port] [log [[disable |
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| | show access-list demo1 command that the
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| default] | [level]] [interval seconds]]
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| | new entry is added in the first position
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| [time-range name] [inactive]
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| | in the ACL and the former first entry
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| Here's an example:asa(config)#
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| | becomes line number two.
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| access-list demo1 permit tcp 10.1.0.0
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| | You can remove an ACE from an ACL by
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| 255.255.255.0 any eq wwwasa(config)#
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| | preceding the ACE configuration statement
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| access-list demo1 permit tcp 10.1.0.0
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| | with the modifier no, as in the following
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| 255.255.255.0 any eq 443asa(config)# show
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| | example:
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| access-list demo1access-list demo1; 2
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| | Asa04(config)#no access-list demo1 deny
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| elementsaccess-list demo1 line 1 extended
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| | tcp host 10.10.2 any eq www
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| permit tcp 10.1.0.0 255.255.255.0 any eq
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| | In my next article, I'll show you how to
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| wwwaccess-list demo1 line 2 extended
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| | use time-ranges to apply access-control
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| permit tcp 10.1.0.0 255.255.255.0 any eq
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| | lists only at certain times and/or on
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| https
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| | certain days. I'll also show you how to
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| In the above example, an ACL called
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| | use object-groups with access-control
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| "demo1" is created in which the first ACE
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| | lists to simplify ACL management by
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| permits TCP traffic originating on the
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| | grouping similar components such as IP
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| 10.1.0.0 subnet to go to any destination
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| | addresses or protocols together.
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| IP address with the destination port of
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|
