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64-10
User Guide for Cisco Security Manager 4.4
OL-28826-01
Chapter 64 Configuring Routing Policies
EIGRP Routing on Cisco IOS Routers
Step 2 On the EIGRP Setup tab, select an EIGRP route from the table, then click Edit, or click Add to create
a route. The EIGRP Setup dialog box appears. See Table 64-6 on page 64-14 for a description of the
fields in this dialog box.
Step 3 Enter the autonomous system number for the route. This number identifies the autonomous system to
other routers.
Step 4 Enter the addresses of the networks to include in the EIGRP route. You can use a combination of
addresses and network/host objects; separate addresses with commas. Click Select to select
network/host objects from a list of existing objects, or to create new network/host objects. For more
information, see Specifying IP Addresses During Policy Definition, page 6-81.
Step 5 Enter the addresses of the passive interfaces, which are interfaces that should not send routing updates
to their neighbors, if any. Enter the names of one or more interfaces or interface roles; separate addresses
with commas. Click Select to select interface names or roles from a list of existing objects, or to create
new interface role objects. For more information, see Specifying Interfaces During Policy Definition,
page 6-70.
Step 6 (Optional) Select Auto-Summary to enable the auto summarization of subnet routes into network-level
routes. Summarization reduces the size of routing tables, thereby reducing the complexity of the
network.
Step 7 Click OK to save your definitions. The EIGRP route appears in the table displayed in the EIGRP Setup
tab.
Defining EIGRP Interface Properties
You can optionally modify the default values of the following two interface properties in a selected
EIGRP autonomous system:
• Hello interval.
• Split horizon.
The hello interval defines the interval between hello packets. Routing devices periodically send these
packets to each other to dynamically learn of other routers on their directly attached networks. This
information is used to discover neighbors and to learn when neighbors become unreachable or
inoperative. By default, hello packets are sent every 5 seconds. The default interval for low speed (T1 or
slower), nonbroadcast multiaccess (NBMA) media is every 60 seconds.
Split horizon is a feature that prevents route information from being sent back in the direction from
which that information originated. If you enable split horizon on an interface (this is the default), update
and query packets are not sent to destinations for which this interface is the next hop. This helps to
prevent routing loops.
For example, as shown in Figure 64-1, if Router One is connected to Routers Two and Three through a
single multipoint interface, and Router One learned about Network A from Router Two, Router One does
not advertise the route to Network A over that same multipoint interface to Router Three. Router One
assumes that Router Three would learn about Network A directly from Router Two.