Disabling eigrp split horizon – Cisco ASA 5505 User Manual

Page 524

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27-16

Cisco ASA 5500 Series Configuration Guide using the CLI

Chapter 27 Configuring EIGRP

Customizing EIGRP

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.

Step 2

hostname(config-router)# network ip-addr

[mask]

Example:

hostname(config)# router eigrp 2

hostname(config-router)# network 10.0.0.0

255.0.0.0

Configures the interfaces and networks that participate in EIGRP
routing. You can configure one or more network statements with
this command.

Directly connected and static networks that fall within the defined
network are advertised by the ASA. Additionally, only interfaces
with an IP address that fall within the defined network participate
in the EIGRP routing process.

If you have an interface that you do not want to have participate
in EIGRP routing, but that is attached to a network that you want
advertised, see the

“Configuring Interfaces for EIGRP” section on

page 27-6

.

Step 3

no default-information

{in | out | WORD}

Example:

hostname(config)# router eigrp 2

hostname(config-router)# network 10.0.0.0

255.0.0.0

hostname(config-router)# no

default-information {in | out | WORD}

Controls the sending or receiving of candidate default route
information.

Entering the no default-information in command causes the
candidate default route bit to be blocked on received routes.
Entering the no default-information out command disables the
setting of the default route bit in advertised routes.

Command

Purpose

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