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

HP STORAGEWORKS ENTERPRISE FILE SERVICES WAN ACCELERATOR DEPLOYMENT GUIDE 53
6 - POLICY-BASED ROUTING
D
EPLOYMENTS
Either PBR or WCCP can be used to redirect traffic from a router to an HP EFS WAN
Accelerator. On some platforms, such as the Cisco 6509 platform on which WCCP
runs, WCCP can redirect only a limited number of TCP ports to the HP EFS WAN
Accelerator without reverting to software forwarding, which has a tendency to spike
the router Central Processing Unit (CPU). On Cisco 6500s running in native mode,
WCCP and PBR can redirect all TCP ports and do all forwarding in the hardware. On
Cisco 6500s running in hybrid mode, only PBR can do hardware redirection for all
ports; WCCP can only do software redirection.
IMPORTANT: HP recommends that you DO NOT use hybrid mode with WCCP in production
environments.
WCCP is designed to redirect traffic to a group of HP EFS WAN Accelerators so it is
often better in clustering solutions. With PBR, any clustering must be done manually
by configuring a set of redirect rules. The following table summarizes the advantages
and disadvantages of PBR and WCCP.
For an example configuration, see “Symmetric Deployments with PBR,
Auto-Discovery, and CDP” on page 66.
How PBR works on a Cisco 6500 Platform,
Version 12.2(17d) SXB1
One of the major issues with PBR is that it can blackhole traffic (that is, drop all TCP
connections to a destination) if the device it is redirecting to fails. To avoid blackholing
traffic, PBR must have a way of tracking whether the PBR next hop is available. You
can enable this tracking feature in a route map with the following Cisco router
command:
set ip next-hop verify-availability
With this command, PBR attempts to verify the availability of the next hop using
information from CDP. If that next hop is unavailable, it skips the actions specified in
the route map.
Capability Platform WCCP PBR
Hardware Redirection
of All TCP Connections
Cisco 6500 Limited numbers of
TCP ports
All TCP traffic.
Clustering All Redirect to a group of
HP EFS WAN
Accelerators
No groups for
redirection. Can be a
manual setup.
Failover All Will only redirect to
active HP EFS WAN
Accelerators in a
group
Requires CDP on the
HP EFS WAN
Accelerator to bypass
an HP EFS WAN
Accelerator that is
down.