Access Control Lists
15-4
15
• Source/Destination Port – Source/destination port number for the specified
protocol type. (Range: 0-65535)
• Source/Destination Port Bit Mask – Decimal number representing the port bits
to match. (Range: 0-65535)
• Control Code – Decimal number (representing a bit string) that specifies flag bits
in byte 14 of the TCP header. (Range: 0-63)
• Control Code Bit Mask – Decimal number representing the code bits to match.
The control bitmask is a decimal number (for an equivalent binary bit mask) that is
applied to the control code. Enter a decimal number, where the equivalent binary
bit “1” means to match a bit and “0” means to ignore a bit. The following bits may
be specified:
•1 (fin) – Finish
• 2 (syn) – Synchronize
• 4 (rst) – Reset
• 8 (psh) – Push
• 16 (ack) – Acknowledgement
• 32 (urg) – Urgent pointer
For example, use the code value and mask below to catch packets with the
following flags set:
• SYN flag valid, use control-code 2, control bitmask 2
• Both SYN and ACK valid, use control-code 18, control bitmask 18
• SYN valid and ACK invalid, use control-code 2, control bitmask 18
