How Routing Behaves Within Fwsm; Egress Interface Selection Process - Cisco 7604 Configuration Manual

Configuring IP Routing and DHCP Services
This chapter describes how to configure IP routing and DHCP on the FWSM. This chapter includes the
following sections:
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How Routing Behaves Within FWSM

FWSM uses both routing table and XLATE tables for routing decisions. To handle
destination-ip-translated, that is, untranslated traffic, FWSM searches for existing XLATE, or static
translation to select the egress interface. The selection process is as follows:

Egress Interface Selection Process

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Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
OL-20748-01
How Routing Behaves Within FWSM, page 8-1
Configuring Static and Default Routes, page 8-2
Defining a Route Map, page 8-5
Configuring BGP Stub Routing, page 8-6
Configuring OSPF, page 8-9
Configuring RIP, page 8-21
Configuring EIGRP, page 8-22
Configuring Asymmetric Routing Support, page 8-30
Configuring Route Health Injection, page 8-32
Configuring DHCP, page 8-35
If destination-ip-translating XLATE already exists, the egress interface for the packet is determined
from the XLATE table, but not from the routing table.
If destination-ip-translating XLATE does not exist, but a matching static translation exists, then the
egress interface is determined from the static route and an XLATE is created, and the routing table
is not used.
If destination-ip-translating XLATE does not exist and no matching static translation exists, the
packet is not destination-ip-translated. FWSM processes this packet by looking up the route to select
egress interface, then source-ip translation is performed (if necessary).
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