Specifications

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Cisco Wide Area Application Services Command Reference

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Chapter 3 CLI Commands

show statistics wccp

To display WCCP statistics for a WAE, use the show statistics wccp EXEC command.

show statistics wccp gre

Syntax Description

Defaults No default behavior or values

Command Modes EXEC

Device Modes application-accelerator

Usage Guidelines GRE is a Layer 3 technique that allows datagrams to be encapsulated into IP packets at the

WCCP-enabled router and then redirected to a WAE (the transparent proxy server). At this intermediate

destination, the datagrams are decapsulated and then routed to an origin server to satisfy the request if a

cache miss occurs. In doing so, the trip to the origin server appears to the inner datagrams as one hop.

Usually, the redirected traffic using GRE is referred to as GRE tunnel traffic. With GRE, all redirection

is handled by the router software.

With WCCP redirection, a Cisco router does not forward the TCP SYN packet to the destination because

the router has WCCP enabled on the destination port of the connection. Instead, the WCCP-enabled

router encapsulates the packet using GRE tunneling and sends it to the WAE that has been configured to

accept redirected packets from this WCCP-enabled router.

After receiving the redirected packet, the WAE does the following:

1. Strips the GRE layer from the packet.

2. Decides whether it should accept this redirected packet and process the request for the content as

follows:

a. If the WAE accepts the request, it sends a TCP SYN ACK packet to the client. In this response

packet, the WAE uses the IP address of the original destination (origin server) that was specified

as the source address so that the WAE can be invisible (transparent) to the client; it acts as if it

is the destination that the client’s TCP SYN packet was trying to reach.

b. If the WAE does not accept the request, it reencapsulates the TCP SYN packet in GRE and sends

it back to the WCCP-enabled router. The router identifies that the WAE is not interested in this

connection and forwards the packet to its original destination (the origin server).

For example, a WAE would not accept the request because it is configured to bypass requests that

originate from a certain set of clients or that are destined to a particular set of servers.

gre Displays WCCP generic routing encapsulation packet-related statistics.