HP StorageWorks Enterprise File Services WAN Accelerator 3.0.4 deployment guide (AG421-96001, March 2007)

52 6 - POLICY-BASED ROUTING DEPLOYMENTS
For detailed information about the factors you must consider before you design and
deploy the HP EFS WAN Accelerator in a network environment, see “Design and
Deployment Overview” on page 17.
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.
Overview of CDP
CDP is a protocol used by Cisco routers and switches to obtain neighbor IP addresses,
model, Internetwork Operating System (IOS) version, and so forth. The protocol runs
at the Open System Interconnection (OSI) layer 2 using the 802.3 Ethernet frame.
HP EFS WAN Accelerators can be deployed in several ways: physically in path,
virtually in path, or out of path. Virtual in-path deployments require that a network
device redirect packets to the HP EFS WAN Accelerators. Network devices that are
capable of redirection are Layer-4 switches, WCCP enabled routers and switches, and
PBR enabled routers.