Dialer Watch Configuration

Dialer watch configuration is built by having an interface monitor a specified route or set of routes.

Dialer Watch Configuration

R4(config-if)# ip addr 172.16.14.1 2 55.255.255.252 R4(config-if)# dialer watch-disable 15 R4(config-if)# dialer watch-group 10

R4(config-if)# exit

R4(config)# dialer watch-list 10 ip 172.16.10.0 2 55.255.255.0

R4(config)# dialer-list 1 protocol ip list 101

R4(config)# access-list 101 remark Define Interesting Traffic

R4(config)# access-list 101 deny ospf any any

R4(config)# access-list 101 permit ip any any

R4(config)# router ospf 1

R4(config-router)# network 172.16.14.0 0.0.0.255 area 0

• Ensures the backup connection is not kept active by OSPF traffic

© 2001, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep v1.0—Mo

ule 3-70

In this example, the BRIO/O interface is part of Open Shortest Path First (OSPF) area 0. You are learning other OSPF routes over the primary link (not shown). You have network 172.16.10.0/24 in the routing table, which is going to be a watched route. Since you are using OSPF, you do not want the OSPF multicast hello packets to constantly bring up the ISDN line, so you mark OSPF traffic as uninteresting in the dialer list.

Dialer Watch Configuration (Cont.)

R4(config-if)# ip addr 172.16.14.1 2 55.255.255.252 R4(config-if)# dialer watch-disable 15

[ Specifies Length of Time Backup

--■ Link Remains Active After Primary

Link Is Established

R4(config-if)# dialer watch-group 10

Binds the list to an interface_J

R4(config)# dialer watch-list 10 ip 172.16.10.0 2 55.255.255.0 R4(config)# dialer-list 1 protocol ip list 101 R4(config)# access-list 101 remark Define Interesting Traffic R4(config)# access-list 101 deny ospf any any R4(config)# access-list 101 permit ip any any R4(config)# router ospf 1

R4(config-router)# network 172.16.14.0 0.0.0.255 area 0

© 2001, Cisco Systems, Inc. All rights reserved. Cisco CCIE Prep vl.O—Module 3-71

The dialer watch-list specifies the route to monitor, 172.16.10.0/24 in this case. You apply that list to the BRI interface with the dialer watch-group command. The dialer watch-disable command delays disconnecting the backup interface for 15 seconds after the primary interface comes back up.

Dialer Watch Operation

Configure the backup link to have a lower routing preference than the primary link. This is done because when the primary link becomes available again, the dynamic routing protocol should prefer the primary over the backup link and not attempt to load-balance across the two links, thus keeping the backup link up indefinitely. The backup link can be configured to be less preferable with any of the following commands; bandwidth, delay or distance as appropriate.

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