HP StorageWorks Enterprise File Services WAN Accelerator Deployment Guide (November 2005)

50 6 - POLICY-BASED ROUTING DEPLOYMENTS
Introduction to PBR
PBR is a router configuration that allows you to define policies to route packets
instead of relying on routing protocols. It is enabled on an interface basis and
packets coming into a PBR-enabled interface are checked to see if they match
the defined policies. If they do match, the packets are applied as the rule
defined for the policy. If they do not match, packets are routed based on the
usual routing table. The rules redirect the packets to a specific IP address.
Typically, you configure PBR on the client-side of the network to redirect
traffic to an HP EFS WAN Accelerator.
IMPORTANT: PBR must be enabled on the interfaces where the client traffic is
arriving and disabled on the interfaces corresponding to the HP EFS WAN Accelerator,
to avoid an infinite loop. (The HP EFS WAN Accelerator can bounce back the packets
it receives either because it is not configured to optimize that traffic or its admission
control is refusing new connections.)
On the server-side, the HP EFS WAN Accelerator is configured as, an out-of-
path device, although it can also be configured with a PBR router with a
specific PBR rule or as an in-path device.
In all cases, the HP EFS WAN Accelerator that intercepts traffic redirected
with PBR is configured with in-path support and PBR support enabled. PBR
policies can be based on the source IP address, destination IP address, protocol
(TCP only), source port, or destination port.
Asymmetric HP EFS WAN Accelerator
Deployments With PBR
The following section describes asymmetric HP EFS WAN Accelerator
deployments with PBR. The examples in this section apply only if the clients
are on one side of the WAN and are connecting to servers on the other side of
the WAN.
If the client-side HP EFS WAN Accelerator is on a different Layer-2 interface
than the clients on the router where PBR is configured, PBR can be enabled on
a Layer-2 interface basis, and redirects TCP traffic going to the server.
IMPORTANT: HP recommends you define a policy based on the source or destination
IP and not on the TCP source or destination ports because certain protocols use
dynamic ports instead of fixed ones such as Exchange and File Transfer Protocol (FTP).