Cisco Wide Area Application Engine 612 Manual de usuario descargar pdf (Pagina 38)

112 Chapter 4: Network Integration and Interception

Protocol (GLBP) to be used for default gateway redundancy. HSRP provides an active/

standby conﬁguration based on a virtual IP (VIP) address. At any given point in time, a

single VIP address is “active” on one of the routers. Hosts are conﬁgured with the HSRP

VIP address as their default gateway, causing all trafﬁc from those hosts to be forwarded to

one of the two routers. In the case of GLBP, either router can be selected as the outbound

path for a host, depending on the speciﬁc GLBP conﬁguration. Because GLBP operates

based on MAC addresses, a WAE running Cisco WAAS appears as a single host. This

means that trafﬁc egressing a WAE will also select one of the two routers to forward

outbound trafﬁc to. For deployments that use GLBP for default-gateway redundancy,

the issue with IP forwarding is the most pronounced.

Figure 4-18 Branch Topology with Multiple Entry and Exit Points

You can see in the previous example how all egress trafﬁc from the WAE is “pinned” to a

single router. This can defeat the purpose of deploying GLBP in the ﬁrst place, which is to

distribute outbound trafﬁc across both routers.

There are several options with WAAS for preserving the network path afﬁnity originally

chosen by the host system or network elements. The ﬁrst two options leverage the WCCPv2

return mechanism. You’ll recall from earlier in this chapter that the WCCPv2 return

mechanism is used by WCCPv2 clients to handle bypass trafﬁc by sending it back to the

WCCPv2-enabled router that redirected it. Cisco WAAS has the ability to leverage the

return method negotiated between the router and WAE for forwarding egress trafﬁc from

WAN

WCCP-Enabled Interface

Outbound traffic is

pinned to a single link!

1 Client sends traffic to its configured default gateway, which

is currently active on the right router (GLBP).

2 Traffic is intercepted by WCCP and redirected to the

WCCP.

3 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 38