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Cisco ASA Series Firewall ASDM Configuration Guide
Chapter 11 Configuring Inspection of Basic Internet Protocols
IP Options Inspection
The Select IP-Options Inspect Map dialog box lets you select or create a new IP Options inspection map. Use this
inspection map to control whether the ASA drops, passes, or clears IP packets containing the following IP
options—End of Options List, No Operations, and Router Alert.
Fields
• Use the default IP-Options inspection map—Specifies to use the default IP Options map. The default
map drops packets containing all the inspected IP options, namely End of Options List (EOOL), No
Operation (NOP), and Router Alert (RTRALT).
• Select an IP-Options map for fine control over inspection—Lets you select a defined application
inspection map or add a new one.
• Add—Opens the Add IP Options Inspect Map dialog box for the inspection.
IP Options Inspect Map
The IP Options Inspect Maps pane lets you view previously configured IP Options inspection maps. An
IP Options inspection map lets you change the default configuration values used for IP Option
inspection.
You can configure IP Options inspection to control which IP packets with specific IP options are allowed
through the security appliance. Configuring this inspection instructs the security appliance to allow a
packet to pass or to clear the specified IP options and then allow the packet to pass.
In particular, you can control whether the security appliance drops, clears, or passes packets containing
the Router Alert (RTRALT) option. Dropping RSVP packets containing the Router Alert option can
cause problems in VoIP implementations. Therefore, you can create IP Options inspection maps to pass
packets containing the RTRALT option.
Fields
IP Options Inspect Maps—Table that lists the defined IP Options inspect maps.
Add—Configures a new IP Options inspect map.
Edit—Edits an existing IP Options inspect map. To edit an IP Options inspect map, choose the entry in
the table and click Edit.
Delete—Deletes the inspect map selected in the IP Options Inspect Maps table.
Add/Edit IP Options Inspect Map
The Add/Edit IP Options Inspect Map lets you configure the settings for IP Options inspection maps.
Fields
• Name—When adding an IP Options inspection map, enter the name of the map. When editing a map,
the name of the previously configured map is shown.
• Description—Enter the description of the IP Options inspection map, up to 200 characters in length.
• Parameters—Select which IP options you want to pass through the ASA or clear and then pass
through the ASA:
–
Allow packets with the End of Options List (EOOL) option
This option, which contains just a single zero byte, appears at the end of all options to mark the end
of a list of options. This might not coincide with the end of the header according to the header length.