Cisco Systems 78-11741-02 manual Passive Interface Examples, IPC-392

Configuring IP Routing Protocol-Independent Features

IP Routing Protocol-Independent Configuration Examples

See more route map examples in the “BGP Route Map Examples” and “BGP Community with Route Maps Examples” sections of the 12.4 BGP documentation.

Passive Interface Examples

The following example configures Ethernet interface 1 as a passive interface under IGRP. Figure 65 shows the router topology. Routing updates are sent out all interfaces in the 192.168/16 network except for Ethernet interface 1.

interface Ethernet 1

ip address 192.168.0.1 255.255.0.0 router igrp 1

network 192.168.0.0 passive-interface Ethernet 1

Figure 65 Filtering IGRP Updates

IGRP router

E1

No routing updates sent to this interface

S1067a

In the following example, as in the first example, IGRP updates are sent out all interfaces in the 192.168/16 network except for Ethernet interface 1. However, in this configuration a neighbor statement is configured explicitly for the 192.168.0.2 neighbor. This neighbor statement will override the passive-interface configuration, and all interfaces in the 192.168/16 network, including Ethernet interface 1, will send routing advertisements to the 192.168.0.2 neighbor.

router igrp 1 network 192.168.0.0

passive-interface ethernet 1 neighbor 192.18.0.2

The passive-interfacecommand disables the transmission and receipt of EIGRP hello packets on an interface. Unlike IGRP or RIP, EIGRP sends hello packets in order to form and sustain neighbor adjacencies. Without a neighbor adjacency, EIGRP cannot exchange routes with a neighbor. Therefore, the passive-interfacecommand prevents the exchange of routes on the interface. Although EIGRP does not send or receive routing updates on an interface configured with the passive-interfacecommand, it still includes the address of the interface in routing updates sent out of other nonpassive interfaces.

Note For more information about configuring passive interfaces in EIGRP, see the How Does the Passive Interface Feature Work in EIGRP? document on cisco.com.

In OSPF, hello packets are not sent on an interface that is specified as passive. Hence, the router will not be able to discover any neighbors, and none of the OSPF neighbors will be able to see the router on that network. In effect, this interface will appear as a stub network to the OSPF domain. This configuration is useful if you want to import routes associated with a connected network into the OSPF domain without any OSPF activity on that interface.

Cisco IOS IP Configuration Guide

IPC-392