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Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
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Chapter 35 Configuring Web Cache Services Using WCCP
Understanding WCCP
4. Once a stable view has been established, one cache engine is elected as the lead cache engine. (The
lead is defined as the cache engine seen by all the cache engines in the cluster with the lowest IP
address). This lead cache engine uses WCCP to indicate to the control router how IP packet
redirection should be performed. Specifically, the lead cache engine designates how redirected
traffic should be distributed across the cache engines in the cluster.
Understanding WCCPv2 Configuration
Multiple routers can use WCCPv2 to service a cache cluster. This is in contrast to WCCPv1 in which
only one router could redirect content requests to a cluster.
Figure 35-2 illustrates a sample configuration
using multiple routers.
Figure 35-2 Cisco Cache Engine Network Configuration Using WCCP v2
The subset of cache engines within a cluster and routers connected to the cluster that are running the
same service is known as a service group. Available services include TCP and User Datagram Protocol
(UDP) redirection.
Using WCCPv1, the cache engines were configured with the address of the single router. WCCPv2
requires that each cache engine be aware of all the routers in the service group. To specify the addresses
of all the routers in a service group, you must choose one of the following methods:
• Unicast—A list of router addresses for each of the routers in the group is configured on each cache
engine. In this case the address of each router in the group must be explicitly specified for each cache
engine during configuration.
• Multicast—A single multicast address is configured on each cache engine. In the multicast address
method, the cache engine sends a single-address notification that provides coverage for all routers
in the service group. For example, a cache engine could indicate that packets should be sent to a
multicast address of 224.0.0.100, which would send a multicast packet to all routers in the service
group configured for group listening using WCCP (see the ip wccp group-listen interface
configuration command for details).
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