72 CHAPTER 4: MANAGING DEVICE S ECURITYFor each TCP flag, the possible field values are:■ Set — Enables the TCP flag.■ Unset — Disables the TCP flag.■ Don’t Care — Does not check the packet’s TCP flag.■ ICMP — If checked, enables filtering ICMP packets for an ICMPmessage type. The possible values are:■ Select from List — Selects an ICMP message type from a list.■ ICMP Type — Specifies an ICMP message type.■ Any — Does not filter for an ICMP message type.■ ICMP Code — If checked, enables specifying an ICMP message codefor filtering ICMP packets. ICMP packets that are filtered by ICMPmessage type can also be filtered by the ICMP message code.■ IGMP — If checked, enables filtering IGMP packets for an IGMPmessage type. The possible values are:■ Select from List — Selects an IGMP message type from a list.■ IGMP Type — Specifies an IGMP message type.■ Any — Does not filter for an IGMP message type.■ Source IP Address — Matches the source IP address to whichpackets are addressed to the ACL.■ Wild Card Mask — Defines the source IP address wildcard mask.Wildcard masks specify which bits are used and which bits areignored. A mask of 255.255.255.255 indicates that no bit isimportant. A mask of 0.0.0.0 indicates that all the bits areimportant. For example, if the source IP address is 149.36.184.198and the wildcard mask is 255.255.255.00, the first three bytes ofthe IP address are ignored, while the last eight bits are used.■ Destination IP Address — Matches the destination IP address towhich packets are addressed to the ACL.■ Wild Card Mask — Indicates the destination IP Address wildcardmask. Wildcards are used to filter a destination IP Address. Masksspecify which bits are used and which bits are ignored. A wildcardmask of 255.255.255.255 indicates that no bit is important. Awildcard mask of 0.0.0.0 indicates that all bits are important. Forexample, if the destination IP address 149.36.184.198 and thewildcard mask is 255.255.0.0, the first two bytes of the IP addressare used, while the last two bytes are ignored.
