Cisco Systems IC-23 Controlling Priority Queueing, Filtering by Protocol Type, IC-53, Command

Configuring LAN Interfaces

Configuring a LAN Extender Interface

Once you have defined an access list to filter by a particular vendor code, you can assign this list to a particular LAN Extender interface so that the interface will then filter based on the MAC source addresses of packets received on that LAN Extender interface. To apply the access list to an interface, use the following command in interface configuration mode:

Command	Purpose
lex input-address-list	Assigns an access list to an interface for filtering by MAC source addresses.
access-list-number

For an example of creating an access list and applying it to a LAN Extender interface, see the “LAN Extender Interface Access List Examples” section.

Filtering by Protocol Type

You can filter by creating a type-code access list and applying it to a LAN Extender interface.

The LAN Extender interface can filter only on bytes 13 and 14 of the Ethernet frame. In Ethernet packets, these two bytes are the type field. For a list of Ethernet type codes, refer to the “Ethernet Type Codes” appendix in the Cisco IOS Bridging and IBM Networking Command Reference, Volume I. In 802.3 packets, these two bytes are the length field.

You can filter by protocol type by creating a protocol-type access list and then applying the access list to an interface.

Note Type-code access lists can have an impact on system performance; therefore, keep the lists as short as possible and use wildcard bit masks whenever possible.

To create a protocol-type access list, use the following command in global configuration mode:

Command	Purpose
access-listaccess-list-number	Creates an access list to filter frames by protocol type.
{permit deny} type-code wild-mask

To apply an access list to an interface, use the following command in interface configuration mode:

Command	Purpose
lex input-type-list access-list-number	Adds a filter for Ethernet- and SNAP-encapsulated packets on input.

For an example of creating an access list and applying it to a LAN Extender interface, see the “LAN Extender Interface Access List Examples” section.

Controlling Priority Queueing

Priority output queueing is an optimization mechanism that allows you to set priorities on the type of traffic passing through the network. Packets are classified according to various criteria, including protocol and subprotocol type. Packets are then queued on one of four output queues.

Cisco IOS Interface Configuration Guide

IC-53