Cisco Wide Area Application Engine 612 Manual de usuario descargar pdf (Pagina 39)

Egress Methods for Intercepted Connections 113

the WAE. The following CLI command changes the default EMIC from IP forwarding to

negotiated return:

egress-method negotiated-return intercept-method wccp

If GRE is the return method negotiated between the WAE and IOS, trafﬁc received on

optimized connections is encapsulated in a GRE header with a destination IP address of the

WCCPv2 router ID and a source IP address of the WAE. When the WCCPv2-enabled IOS

device receives the GRE-encapsulated packet, it removes the GRE header and forwards the

packet normally. Because the GRE header uses a source IP address of the WAE, the IOS

WCCPv2 process knows not to re-intercept the packet. This capability to return trafﬁc to

the IOS device that redirected it allows for the preservation of the original path selection

made by the host or network infrastructure.

Another beneﬁt of the GRE return method is that the WAE can reside on the same IP subnet

with clients or servers that it optimizes connections for. This greatly simpliﬁes branch

deployments by removing the requirement for a separate subnet dedicated to the WAE.

Figure 4-19 shows the same topology as Figure 4-18, except using the negotiated return

EMIC instead of IP forwarding.

Figure 4-19 Branch Topology Using GRE Return EMIC

WAN

WCCP-Enabled Interface

Outbound traffic is

pinned to a single link!

• Client sends traffic to its configured default gateway, which

is currently active on the right-hand router (GLBP).

• Traffic is intercepted by WCCP and redirected to the

WCCP.

• Egress traffic from the WAE is sent transparently to its

default gateway.

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Cisco Wide Area Application Engine 612 Manual de usuario Pagina 39