Appendix B

Requirements for Transparent Proxying

About this appendix

This appendix lists the requirements for implementing transparent proxying when you are using an L4 or L7 switch or a WCCP 2.0-based router. This appendix also provides key features to look for when purchasing switches.

Requirements for transparent proxying with a switch

To deploy transparent proxying with an L4 or L7 switch, meet the requirements listed in the following table. Network Appliance also recommends that you comply with the "best practice" recommendations that are listed in the table. Items in the table are requirements unless otherwise noted.

Category	Requirements and recommendations
NetCache appliance	A network interface is required for each switch attached. The NetCache appliance should be directly connected to the switch (best practice).
Network layout	The switch must be in a location to detect all traffic for the clients it is expected to serve.
L4 or L7 switch configuration	Switch configuration involves the following high-level steps: Identify traffic to be redirected to the NetCache appliances and the request distribution method to be used. Identify the NetCache appliances to which traffic is to be redirected. Contact your switch vendor for specific switch configuration settings.
NetCache configuration	For each protocol for which you want to set up transparent proxying, enable the transparency feature. See the online Help for configuration details.

Requirements for transparent proxying with a WCCP 2.0 router

To deploy transparent proxying with a WCCP router, meet the requirements listed in the following table.

Category	Requirements and recommendations
NetCache appliance	A network interface is required for each router attached.
Network layout	The router must be in a location to detect all traffic for the clients it is expected to serve.
Router configuration	Router configuration includes configuring WCCP service group information to correspond to service group configuration on the NetCache appliances. See Cisco documentation for information about setting up WCCP 2.0.
NetCache configuration	Configuring the NetCache appliance for transparent proxying with a WCCP router includes the following: For each protocol for which you want to set up transparent proxying, enable the transparency feature. Configure service group information, which includes identifying traffic to be redirected to the NetCache appliances and the request distribution method to be used. NetCache can then send information to the router that router can use to configure itself. See the online Help for configuration details.

Key features for switches

When evaluating switches to use for transparent proxying, look for the following key features:

For Web caching or streaming media caching, failover routing to the local or remote server when all Web caches or streaming media caches fail
A flexible algorithm for distributing requests among the NetCache appliances
The capability to limit the number of connections to a particular NetCache appliance
For Web caching service and streaming media caching, support for access control lists so that service can be disabled for particular Web servers, streaming servers, and clients
The capability to detect failure of the NetCache appliance by using HTTP to poll the cache
The capability to detect and avoid potential routing loops from NetCache appliance redirection that can occur between the switch, routing equipment, and NetCache appliances
Administrative security
Redundant switch failover deployment
The capability to load balance to NetCache appliances on different subnets