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Tags: dns dynamic dns cisco routers www.blindhog.net
Clipped on: 2013-03-05

Cisco Routers and Dynamic DNS

Posted by Josh on Thu 19 Aug 2010
Categories: Cisco , Cisco Routers , Voice LAB - [12] Comments 

This short post demonstrates using ‘ip sla’ and  freedns.afraid.org for dynamic dns.



If you are not familiar with FreeDNS, it is simply a free / shared dns host. Individuals voluntarily host their domains on the FreeDNS servers and allow other users to create dns subdomains with their domain name.



Here are the steps


  1. Create an account with the FreeDNS website


  • Add a new subdomain
    1. Click the ‘Registry’ link
    2. Click on a domain you would like to link to…e.g. mooo.com
    3. Enter text in the subdomain field … e.g. blindhog


  • Get the dynamic dns url
    1. Click the ‘Dynamic DNS’ link
    2. Right-Click on the ‘Direct URL’ link next to your new subdomain and select ‘Copy Link Location’
    3. Paste this link into notepad. We will use it later.


  • Login to your cisco router and get into config mode.


  • Configure  an ‘http get’ based sla monitorNote: Only enter the first part of the url (before the question mark) and do not hit enter. Press ‘ctrl+v’ then enter the second half of the url including the question mark. If you do not use ‘ctrl+v’ before the question mark will be used to display options of the ‘http get’ command.

    ip sla 1
    http get http://freedns.afraid.org/dynamic/update.php

    ip sla monitor 1
    type http operation get ur
    l http://freedns.afraid.org/dynamic/update.php?VEc..




  • Create a new ip sla schedule to activate the update.
    ip sla schedule 1 lifetime forever start-time now


    ip sla monitor schedule 1 life forever start-time now

  • Use the following commands to troubleshoot

    show ip sla configuration
    show ip sla statistics

    debug ip sla trace
    debug ip sla error


    show ip sla monitor configuration
    show ip sla monitor statistics

    debug ip sla monitor trace
    debug ip sla monitor error