Chapter 9
| Access Control Lists
IPv4 ACLs
– 325 –
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)#
Related Commands
access-list ip (320)
Time Range (141)
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