Cisco Systems 4500 Restrictions for WCCP

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Software Configuration Guide—Release 15(02)SG
OL-23818-01
Chapter 64 Configuring WCCP Version 2 Services Restrictions for WCCP
Web Content Packet Return
If a content engine is unable to provide a requested object it has cached due to error or overload, the
content engine returns the request to the router for onward transmission to the originally specified
destination server. WCCP verifies which requests have been returned from the content engine
unserviced. Using this information, the router can then forward the request to the originally targeted
server (rather than attempting to resend the request to the content cluster). This provides error handling
transparency to clients.
Typical reasons why a content engine would reject packets and initiate the packet return feature include
the following:
• Instances when the content engine is overloaded and has no room to service the packets.
• Instances when the content engine is filtering for certain conditions that make caching packets
counterproductive (such as, when IP authentication has been turned on).
Restrictions for WCCP
The following limitations apply to WCCP:
• WCCP works only with IPv4 networks.
• For routers servicing a multicast cluster, the time to live (TTL) value must be set at 15 or fewer.
• Because the WCCP protocol messages may now be IP multicast, members may receive messages
that are not relevant or (are) duplicates. Appropriate filtering need to be performed.
• A service group can comprise up to 32 content engines and 32 routers.
• All content engines in a cluster must be configured to communicate with all routers servicing the
cluster.
• Up to 8 active service groups are supported on a switch. Up to 8 service groups can be configured
simultaneously on the same client interface.
• The Layer 2 rewrite forwarding method is supported (in hardware), the GRE encapsulation
forwarding method is not supported.
• The GRE return method is supported in software. The Layer 2 return method is supported in
hardware and is recommended.
• Direct Layer 3 connectivity to content engines is required; Layer 3 connectivity of one or more hops
away is not supported.
• The following apply only to Supervisor Engine 6-E, Supervisor Engine 6L-E, Catalyst 4900M,
Catalyst 4948E, and Supervisor Engine 7-E:
– Redirect ACL is supported.
– Output redirection is supported in addition to input redirection.
– Input/output redirection configuration is not supported on content engine facing interfaces.
– When the TCAM space is exhausted on a supervisor engine, traffic is redirected in software. On
all other supervisor engines, traffic is not redirected; it is forwarded normally.
• WCCP version 2 standard allows for support of up to 256 distinct masks. However, a Catalyst 4500
series switch only supports mask assignment table with a single mask.
• Valid multicast addresses are from 224.0.0.0 to 239.255.255.255.