Cisco Catalyst 4500 Series - Overview

81-2
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 81 Configuring WCCP Version 2 Services
Understanding WCCP
Overview
The Cisco IOS WCCP feature allows use of Cisco Content Engines (or other content engines running
WCCP) to localize web traffic patterns in the network, enabling content requests to be fulfilled locally.
Traffic localization reduces transmission costs and download time.
WCCP enables Cisco IOS routing platforms to transparently redirect content requests. The main benefit
of transparent redirection of HTTP/non-HTTP requests is that users need not configure their browsers
to use a web proxy. Instead, they can use the target URL to request content, and have their requests
automatically redirected to a content engine. The word “transparent” in this case means that the end user
does not know that a requested file (such as a web page) came from the content engine instead of from
the originally specified server.
When a content engine receives a request, it attempts to service it from its own local content. If the
requested information is not present, the content engine issues its own request to the originally targeted
server to get the required information. When the content engine retrieves the requested information, it
forwards it to the requesting client and caches it to fulfill future requests, thus maximizing download
performance and substantially reducing transmission costs.
WCCP enables a series of content engines, called a content engine cluster, to provide content to a router
or multiple routers. Network administrators can easily scale their content engines to handle heavy traffic
loads using these clustering capabilities. Cisco clustering technology enables each content member to
work in parallel, resulting in linear scalability. Clustering content engines greatly improves the
scalability, redundancy, and availability of your caching solution. You can cluster up to 32 content
engines to scale to your desired capacity.
Beginning in Cisco IOS XE Release 3.7.1E, WCCPv2 is supported on Virtual Switching System (VSS)
on Cisco Catalyst 4500-E (Supervisor Engine 7-E and Supervisor Engine 8-E) and Cisco Catalyst
4500-X switches, on the IP Base image and the Enterprise Services image.
Beginning in Cisco IOS XE Release 3.8.0E, WCCPv2 supports traffic redirection to and from Virtual
Routing and Forwarding (VRF) interfaces. Ensure that you configure the content engine running WCCP
such that the forward and return traffic, to and from the content engine, is from interfaces that are a part
of the same VRF. The VRF used for WCCP on an interface should match the VRF configured on that
interface.
Hardware Acceleration
Hardware Acceleration is enabled by default on Catalyst 4500 series switches. Layer 2 rewrite
forwarding and Layer 2 return method are supported in hardware.
When the switch exhausts hardware (TCAM) or software resources, traffic is redirected in software.
GRE return method is supported only in software.
Configure a directly connected content engine to negotiate use of the WCCP Layer 2 Redirection feature
(with load balancing) based on the mask assignment table. The show ip wccp web-cache detail
command displays the redirection method in use for each cache.
Note You can configure the Cisco Content Engine Release 2.2 or later to use the WCCP Layer 2
Redirection feature with the mask assignment table.