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Counting ACL Hits
You can view the number of packets matching the ACL by using the count option when creating ACL entries.
1. Create an ACL that uses rules with the count option. Refer to Configuring a Standard IP ACL Filter.
2. Apply the ACL as an inbound or outbound ACL on an interface. Refer to Assign an IP ACL to an Interface.
3. show ip accounting access-list
EXEC Privilege mode
View the number of packets matching the ACL.
Configure Ingress ACLs
Ingress ACLs are applied to interfaces and to traffic entering the system.
These system-wide ACLs eliminate the need to apply ACLs onto each interface and achieves the same results. By localizing
target traffic, it is a simpler implementation.
To create an ingress ACL, use the ip access-group command in EXEC Privilege mode. The example shows applying the
ACL, rules to the newly created access group, and viewing the access list.
Example of Applying ACL Rules to Ingress Traffic and Viewing ACL Configuration
To specify ingress, use the in keyword. Begin applying rules to the ACL with the ip access-list extended abcd
command. To view the access-list, use the show command.
Dell(conf)#interface tengige 0/0
Dell(conf-if-te-0/0)#ip access-group abcd in
Dell(conf-if-te-0/0)#show config
!
TengigEthernet 0/0
no ip address
ip access-group abcd in
no shutdown
Dell(conf-if-te-0/0)#end
Dell#configure terminal
Dell(conf)#ip access-list extended abcd
Dell(config-ext-nacl)#permit tcp any any
Dell(config-ext-nacl)#deny icmp any any
Dell(config-ext-nacl)#permit 1.1.1.2
Dell(config-ext-nacl)#end
Dell#show ip accounting access-list
!
Extended Ingress IP access list abcd on tengigEthernet 0/0
seq 5 permit tcp any any
seq 10 deny icmp any any
seq 15 permit 1.1.1.2
Configure Egress ACLs
Configuring egress ACLs onto physical interfaces protects the system infrastructure from attack — malicious and incidental —
by explicitly allowing only authorized traffic
These system-wide ACLs eliminate the need to apply ACLs onto each interface and achieves the same results. By localizing
target traffic, it is a simpler implementation.
To restrict egress traffic, use an egress ACL. For example, when a direct operating system (DOS) attack traffic is isolated to a
specific interface, you can apply an egress ACL to block the flow from the exiting the box, thus protecting downstream devices.
To create an egress ACL, use the ip access-group command in EXEC Privilege mode. The example shows viewing the
configuration, applying rules to the newly created access group, and viewing the access list.
Access Control Lists (ACLs)
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