Cisco ASA 5505 Configuration Manual page 437

Chapter 23 Configuring EIGRP
Add network rules to the network rule table. The network rules define which networks are allowed and
Step 6
which are not when receiving or sending default route information. Repeat the following steps for each
network rule you are adding to the default information filter rule.
a.
b.
c.
d.
Click OK to accept the default information filter rule.
Step 7
Disabling EIGRP Split Horizon
Split horizon controls the sending of EIGRP update and query packets. When split horizon is enabled on
an interface, update and query packets are not sent for destinations for which this interface is the next
hop. Controlling update and query packets in this manner reduces the possibility of routing loops.
By default, split horizon is enabled on all interfaces.
Split horizon blocks route information from being advertised by a router out of any interface from which
that information originated. This behavior usually optimizes communications among multiple routing
devices, particularly when links are broken. However, with nonbroadcast networks, there may be
situations where this behavior is not desired. For these situations, including networks in which you have
EIGRP configured, you may want to disable split horizon.
If you disable split horizon on an interface, you must disable it for all routers and access servers on that
interface.
To disable EIGRP split horizon, perform the following steps:
In the main ASDM window, choose Configuration > Device Setup > Routing > EIGRP > Interfaces.
Step 1
The Interface pane appears and displays the EIGRP interface configurations.
Double-click an interface entry or choose the entry and click Edit.
Step 2
The Edit EIGRP Interface Entry dialog box appears.
Choose the EIGRP Autonomous system (AS) number from the drop-down list.
Step 3
This list is populated from system numbers that were set up when you enabled the EIGRP routing
process.
Uncheck the Split Horizon check box.
Step 4
Click OK.
Step 5
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Click Add to add a network rule. Double-click an existing network rule to edit the rule.
In the Action field, click Permit to allow the network or Deny to block the network.
Enter the IP address and network mask of the network being permitted or denied by the rule in the
IP Address and Network Mask fields.
To deny all default route information from being accepted or sent, enter 0.0.0.0 as the network
address and choose 0.0.0.0 as the network mask.
Click OK to add the specified network rule to the default information filter rule.
Cisco ASA 5500 Series Configuration Guide using ASDM
Customizing EIGRP
23-17