Choosing a WCCP traffic redirection method

Types of WCCP traffic redirection

You can configure a WCCP router to redirect client or server traffic to NetCache using the following methods:

IP-GRE encapsulation
In IP-GRE encapsulation, the original IP packet is encapsulated in another IP packet containing the appliance's IP address. IP-GRE encapsulation is the default traffic redirection method.

Note
IP-GRE packets that pass through a transparent firewall to the appliance are not reencapsulated when NetCache sends them to clients.
MAC address rewriting
In MAC address rewriting (sometimes referred to as L2 rewriting), the router replaces the original MAC address with the address of the target proxy- cache server. This method can be used only when the WCCP router and appliance are on the same subnet.

To configure the client traffic redirection method, use the Redirection Method option. To configure the server traffic redirection method, use the Return Method option. You can access both options by selecting Setup tab > Transparency > WCCP Global Settings.

How to choose a traffic redirection method

When deciding whether to modify the WCCP traffic redirection method, consider the information in the following table.

If...	Use this redirection method...	Comments
You are concerned about redirection efficiency	MAC address rewriting	MAC address rewriting redirects traffic more quickly than does IP-GRE encapsulation. However, MAC address rewriting can be used only when the WCCP router and appliance are on the same subnet.
The router and appliance are on different subnets	IP-GRE encapsulation	IP-GRE can be used when the router and appliance are on the same subnet or on different subnets.
You need to use IP spoofing	IP-GRE encapsulation	MAC address rewriting cannot be used in IP spoofing deployments. See Retaining the client IP address as the source IP address for more information.

If...

Use this redirection method...

Comments

You are concerned about redirection efficiency

MAC address rewriting

MAC address rewriting redirects traffic more quickly than does IP-GRE encapsulation.

However, MAC address rewriting can be used only when the WCCP router and appliance are on the same subnet.

The router and appliance are on different subnets

IP-GRE encapsulation

IP-GRE can be used when the router and appliance are on the same subnet or on different subnets.

You need to use IP spoofing

IP-GRE encapsulation

MAC address rewriting cannot be used in IP spoofing deployments. See Retaining the client IP address as the source IP address for more information.

WCCP traffic redirection requirements for request forwarding

If you have enabled one or more of the request forwarding options, you can use MAC address rewriting only if the appliances are connected to the server-side router interface. If you use IP-GRE encapsulation, you can use any interface on the router to redirect traffic to the appliances. See Circumventing transparent redirection of client requests for more information about request forwarding.

See the Cisco documentation for information about additional limitations of MAC address rewriting.