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Chapter43 Configuring Web Cache Services By Using WCCP
Understanding WCCP
You can configure up to 8 service groups on a switch and up to 32 clients per service gro up. W C CP
maintains the priority of the service group in the group definition. WCCP uses the priority to configure
the service groups in the switch hardware. For example, if service group 1 has a priority of 100 and looks
for destination port 80, and service group 2 has a priority of 50 and lo oks for source port 80, the incoming
packet with source and destination port 80 is forwarded by using service group 1 because it has the
higher priority.
WCCP supports a cluster of application engines for every service group. Re dire cted t raffic can be sent
to any one of the application engines. The switch supports the ma sk assign me nt m eth od of l oad
balancing the traffic among the application engines in the cluster for a service group.
After WCCP is configured on the switch, the switch forwards all service group packets received from
clients to the application engines. However, these packets are not redirected:
•Packets originating from the application engine and targeted to the web server.
•Packets originating from the application engine and targeted to the client.
•Packets returned or rejected by the application engine. These packets are sent to the web server.
You can configure a single multicast address per service group for sending and receiving protocol
messages. When there is a single multicast address, the application engine sends a notification to one
address, which provides coverage for all routers in the service group, for example, 225.0.0.0. If you add
and remove routers dynamically, using a single multicast address provides easier configuration because
you do not need to specifically enter the addresses of all devices in the WCCP network.
You can use a router group list to validate the protocol packets received from the application engine.
Packets matching the address in the group list are processed, packets not matching the g roup list address
are dropped.
To disable caching for specific clients, servers, or client/server pairs, you can use a WCCP redirect
access control list (ACL). Packets that match the red ire ct ACL bypass t he cach e a nd are fo rwa rde d
normally.
Before WCCP packets are redirected, the switch examines ACLs associated with a ll i nbound fe atu res
configured on the interface and permits or denies packet for wardi ng ba se d on how th e pa cke t ma tch es
the entries in the ACL.
When packets are redirected, the output ACLs associated with the redirec ted int erf ace ar e applied to the
packets. Any ACLs associated with the original port are not applied unless you specifically configure
the required output ACLs on the redirected interfaces.
WCCP and Switch Stacks
WCCP support is the same for a switch stack as for a standalone switch. WCCP configuration
information is propagated to all switches in the stack. All switches in the stack, including the stack
master, process the information and program their hardware. For more information abo ut switch stacks,
see Chapter5, “Managing Switch Stacks.”
The stack master performs these WCCP functions:
•It receives protocol packets from any WCCP-enabled interface and sends the m out any
WCCP-enabled interface in the stack.
•It processes the WCCP configuration and propagates the information to all stack members.
•It distributes the WCCP information to any switch that joins the stack.
•It programs its hardware with the WCCP information it processes.
Stack members receive the WCCP information from the master switch and program their hardware.