Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

ISDN-Backup for DSL Connection

I need to integrate a ISDN-backup Solution for an existing DSL Connection.

The DSL-Conection is done by using a Dialer with IP address negotiated but I always get the same one (static). Now I want to backup the case if the DSL-Connection seems to work but no IP could be transfered (Cause very seldom i get a link down at the ATM interface!!). So I need to set up a function which checks if IP works and if not it has to start a Dial-Out ISDN connection. For this connection I even could define that I get the same address negotiated like for the DSL-Connection (if it make sense!!) Any idea?? many thanks in advance. Matt

VIP Purple

Re: ISDN-Backup for DSL Connection

Hello Martin,

try Enhanced Object Tracking, which checks the reachability of the remote next hop address, and, if that address is not reachable, considers the primary connection down. Your configuration would look something like this (the IP addresses in this example obviously are arbitrary):

interface ATM0

description primary_link

no ip address

pvc 0/33

pppoe-client dial-pool-number 1


interface BRI0

description backup_link

ip address


rtr 1

type echo protocol ipIcmpEcho

timeout 1000

frequency 3

threshold 2

rtr schedule 1 life forever start-time now

track 123 rtr 1 reachability

access list 101 permit icmp any host echo

route map MY_LOCAL_POLICY permit 10

match ip address 101

set interface null 0


ip local policy route-map MY_LOCAL_POLICY

ip route track 123

ip route 254

In newer IOS versions (that is,12.4), the 'rtr' command has been replaced by the 'sla' command, but the functionality is the same.

There are also other parameters you can track. Have a look at the documents below:

Cisco IOS Software Releases 12.3 Special and Early Deployments

Reliable Static Routing Backup Using Object Tracking

Configuring Enhanced Object Tracking



CreatePlease to create content