General steps for planning and configuring ACLs

  1. Identify the ACL action to apply. As part of this step, determine the best points at which to apply specific ACL controls. For example, you can improve network performance by filtering unwanted IPv4 traffic at the edge of the network instead of in the core. Also, on the switch itself, you can improve performance by filtering unwanted IPv4 traffic where it is inbound to the switch instead of outbound.
    CAUTION: Regarding the use of source routing: Source routing is enabled by default on the switch and can be used to override ACLs. For this reason, if you are using ACLs to enhance network security, the recommended action is to use the no ip source-route command to disable source routing on the switch. (If source routing is disabled in the running-config file, the show running command includes “ no ip source-route ” in the running-config file listing.)

    Traffic source

    ACL application

    IPv4 or IPv6 traffic from a specific, authenticated client

    dynamic port ACL (RADIUS-assigned ACL) for inbound IP traffic from an authenticated client on a port

    IPv4 traffic entering the switch on a specific port

    static port ACL (static-port assigned) for any inbound IPv4 traffic on a port from any source

    switched or routed IPv4 traffic entering the switch on a specific VLAN


  2. Identify the traffic types to filter.
    • The SA and/or the DA of traffic you want to permit or deny. This can be a single host, a group of hosts, a subnet, or all hosts.

    • Traffic of a specific IPv4 protocol type (0-255)

    • Any TCP traffic (only) for a specific TCP port or range of ports, including optional control of connection traffic based on whether the initial request should be allowed

    • All UDP traffic or UDP traffic for a specific UDP port

    • All ICMP traffic or ICMP traffic of a specific type and code

    • All IGMP traffic or IGMP traffic of a specific type

    • Any of the above with specific precedence and/or ToS settings

  3. Design the ACLs for the control points (interfaces) selected. When using explicit "deny" ACEs, optionally use the VACL logging feature for notification that the switch is denying unwanted packets.
  4. Configure the ACLs on the selected switches.
  5. Assign the ACLs to the interfaces you want to filter, using the ACL application (static port ACL) appropriate for each assignment.
  6. Test for desired results.