Applying Acls To A Physical Interface; Displaying Acl Information; Displaying Acls - Cisco Catalyst 2950 Software Configuration Manual

Displaying ACL Information

Applying ACLs to a Physical Interface

Beginning in privileged EXEC mode, follow these steps to control access to a Layer 2 interface:
Command
Step 1 configure terminal
Step 2 interface interface-id
Step 3
ip access-group {access-list-number |
name} {in}
Step 4
end
Step 5 show running-config
Step 6 copy running-config startup-config
This example shows how to apply access list 2 on an interface to filter packets entering the interface:
Switch(config)# interface gigabitethernet0/2
Router(config-if)# ip access-group 2 in
The ip access-group interface configuration command is only valid when applied to a management
Note
interface or a Layer 2 physical interface. ACLs cannot be applied to interface port-channels.
For inbound ACLs, after receiving a packet, the switch checks the packet against the ACL. If the ACL
permits the packet, the switch continues to process the packet. If the ACL rejects the packet, the switch
discards the packet.
When you apply an undefined ACL to an interface, the switch acts as if the ACL has not been applied to
the interface and permits all packets. Remember this behavior if you use undefined ACLs for network
security.
Displaying ACL Information
You can display the ACLs that are configured on the switch, and you can display the ACLs that have
been applied to physical and management interfaces. This section consists of these topics:
•
•

Displaying ACLs

You can display existing ACLs by using show commands.
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
28-20
Purpose
Enter global configuration mode.
Identify a specific interface for configuration and enter interface
configuration mode.
The interface must be a Layer 2 or management interface or a management
interface VLAN ID.
Control access to the specified interface.
Return to privileged EXEC mode.
Display the access list configuration.
(Optional) Save your entries in the configuration file.
Displaying ACLs, page 28-20
Displaying Access Groups, page 28-22
Chapter 28 Configuring Network Security with ACLs
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