SMC Networks SMC8624/48T manual 122

COMMAND LINE INTERFACE

•The control-code bitmask is a decimal number (representing an equivalent 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 2”

-Both SYN and ACK valid, use “control-code 18 18”

-SYN valid and ACK invalid, use “control-code 2 18”

Example

This example accepts any incoming packets if the source address is within subnet 10.7.1.x. For example, if the rule is matched; i.e., the rule (10.7.1.0

&255.255.255.0) equals the masked address (10.7.1.2 & 255.255.255.0), the packet passes through.

Console(config-ext-acl)#permit 10.7.1.1 255.255.255.0 any Console(config-ext-acl)#

This allows TCP packets from class C addresses 192.168.1.0 to any destination address when set for destination TCP port 80 (i.e., HTTP).

Console(config-ext-acl)#permit 192.168.1.0 255.255.255.0 any destination-port 80

Console(config-ext-acl)#

This permits all TCP packets from class C addresses 192.168.1.0 with the TCP control code set to “SYN.”

Console(config-ext-acl)#permit tcp 192.168.1.0 255.255.255.0 any control-flag 2 2

Console(config-ext-acl)#

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