In certain cases, it is not advantageous or even possible to deploy the BIG-IP system inline. For example, in the case of a collapsed backbone where the WAN router and the LAN switch are in one physical device, you might not be able to deploy the BIG-IP system inline.
If you choose not to deploy the BIG-IP system inline, you can use a one-arm deployment. In a one-arm deployment, the BIG-IP system has a single (hence, one-arm) connection to the WAN router or LAN switch. The WAN router (or switch) redirects all relevant traffic to the BIG-IP system. In this configuration, the WAN router typically uses Web Cache Communication Protocol version 2 (WCCPv2) to redirect traffic to the BIG-IP system.
The traffic flow sequence in this illustration is as follows:
TMOS includes support for Web Cache Communication Protocol version 2 (WCCPv2). WCCPv2 is a content-routing protocol developed by Cisco Systems. It provides a mechanism to redirect traffic flows in real time. The primary purpose of the interaction between WCCPv2-enabled routers and a BIG-IP system is to establish and maintain the transparent redirection of selected types of traffic flowing through those routers.
To use WCCPv2, you must enable WCCPv2 on one or more routers connected to the BIG-IP system, and configure a service group on the BIG-IP system that includes the router information. The BIG-IP system then receives all the network traffic from each router in the associated service group, and determines both the traffic to optimize and the traffic to which to apply a service.
In configuring WCCPv2 on a network, you define a service group on the BIG-IP system, which is a collection of WCCPv2 services configured on the BIG-IP system. A WCCPv2 service in this context is a set of redirection criteria and processing instructions that the BIG-IP system applies to any traffic that a router in the service group redirects to the BIG-IP system. Each service matches a service identifier on the router.
The following illustration shows a one-arm configuration on one side of the WAN and an inline (bridge) configuration on the other side.
Before you configure an iSession connection on the BIG-IP system, make sure that you have completed the following general prerequisites.
To use WCCPv2 for traffic redirection, you configure a service group on the BIG-IP system that includes at least one service. You also configure this service on the WCCPv2-enabled router connected to the BIG-IP system.
For optimization, you also need to configure the BIG-IP system on the other side of the WAN to complete the connection. The BIG-IP system on the other side of the WAN can be set up in either a one-arm or inline configuration.
Before you begin configuring WCCPv2 for traffic redirection, ensure that you have performed the following actions on the other devices in your network.