Cisco Wide Area Application Engine 612 Manual de usuario descargar pdf (Pagina 37)

Egress Methods for Intercepted Connections 111

Figure 4-17 ACE Deployed Using Routed Mode

ACE is typically deployed in conjunction with WAAS using transparent, or directed, mode.

This means that the ACE module does not perform any Network Address Translation (NAT)

of trafﬁc passing through it.

Egress Methods for Intercepted Connections

Cisco WAAS provides several options for handling egress trafﬁc received on intercepted

connections. These options allow for ﬂexibility when determining where to integrate

WAAS into the existing network infrastructure, and help preserve the original path

selection for trafﬁc ﬂows. These deployment options, referred to as the egress methods

for intercepted connections (EMIC), are discussed in detail in this section.

The ﬁrst EMIC available in Cisco WAAS is IP forwarding. Egress trafﬁc received on

intercepted connections is forwarded based on the conﬁguration of the local WAE routing

table, which typically means that trafﬁc is forwarded to the conﬁgured default gateway. In

addition to supporting a single default gateway, WAAS supports up to 1024 static routes.

Static routes are conﬁgured with a next hop IP address of a directly connected interface;

recursive next hop IP addresses are not supported. Although it is possible to conﬁgure

multiple static routes for the same destination, there is no support for equal-cost multipath

(ECMP). Only a single route will be installed in the routing table at a time. It should be

noted that trafﬁc originating from the WAE itself will also use IP forwarding, regardless of

the EMIC conﬁguration. The IP forwarding EMIC is suited for very basic topologies where

only a single egress path for trafﬁc exists, or in situations where other EMICs are not

supported.

For more complex topologies, the IP forwarding EMIC can lead to undesirable forwarding

of trafﬁc for intercepted connections. Take for example the topology shown in Figure 4-18.

This example shows a remote ofﬁce with multiple WAN routers connecting to diverse

circuits. Trafﬁc can enter or leave the site through either router. When multiple paths exist

for trafﬁc leaving a site, it is common for either HSRP or the Gateway Load Balancing

WAN

VLAN 10

10.10.10.0/24

Server Default Gateway

VLAN 20

10.10.10.0/24

Cisco ACE

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Cisco Wide Area Application Engine 612 Manual de usuario Pagina 37