Layer 2 Forwarding Redirection And Return - Cisco ASR 1000 Series Configuration Manual

WCCPv2—IPv6 Support
A content engine receiving a request attempts to service it from its own local cache. If the requested information
is not present, the content engine issues its own request to the originally targeted server to get the required
information. A content engine retrieving the requested information forwards it to the requesting client and
caches it to fulfill future requests, thus maximizing download performance and substantially reducing
transmission costs.
WCCP enables a series of content engines, called a content engine cluster, to provide content to a router or
multiple routers. Network administrators can easily scale their content engines to manage heavy traffic loads
through these clustering capabilities. Cisco clustering technology enables each cluster member to work in
parallel, resulting in linear scalability. Clustering content engines greatly improves the scalability, redundancy,
and availability of your caching solution. You can cluster up to 32 content engines to scale to your desired
capacity.

Layer 2 Forwarding Redirection and Return

WCCP uses either generic routing encapsulation (GRE) or Layer 2 (L2) to redirect or return IP traffic. When
WCCP forwards traffic via GRE, the redirected packets are encapsulated within a GRE header. The packets
also have a WCCP redirect header. When WCCP forwards traffic using L2, the original MAC header of the
IP packet is overwritten and replaced with the MAC header for the WCCP client.
Using L2 as a forwarding method allows direct forwarding to the content engine without further lookup. Layer
2 redirection requires that the router and content engines are directly connected, that is, on the same IP
subnetwork.
When WCCP returns traffic via GRE, the returned packets are encapsulated within a GRE header. The
destination IP address is the address of the router and the source address is the address of the WCCP client.
When WCCP returns traffic via L2, the original IP packet is returned without any added header information.
The router to which the packet is returned will recognize the source of the packet and prevent redirection.
The WCCP redirection method does not have to match the return method.
L2 forwarding, return, or redirection are typically used for hardware-accelerated platforms. Depending on
your release, L2 forwarding, return, and redirection can also be used for software-switching platforms.
On Cisco ASR 1000 Series Aggregation Services Routers, both the GRE and L2 forward and return methods
use the hardware. Therefore, there is no significant performance degradation between them.
For content engines running Application and Content Networking System (ACNS) software, use the wccp
custom-web-cache command with the l2-redirect keyword to configure L2 redirection. For content engines
running Cisco Wide Area Application Services (WAAS) software, use the wccp tcp-promiscuous command
with the l2-redirect keyword to configure L2 redirection.
For information about Cisco ACNS commands used to configure Cisco Content Engines, see the
Software Command
For more information about WAAS commands used to configure Cisco Content Engines, see the
Area Application Services Command
WCCP Mask Assignment
The WCCP Mask Assignment feature enables mask assignment as the load-balancing method (instead of the
default hash assignment method) for a WCCP service.
For content engines running Application and Content Networking System (ACNS) software, use the wccp
custom-web-cache command with the mask-assign keyword to configure mask assignment. For content
Reference.
Reference.
IP Application Services Configuration Guide, Cisco IOS XE Release 3S (Cisco ASR 1000)
Layer 2 Forwarding Redirection and Return
Cisco ACNS
Cisco Wide
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