Switching ISP & IP addresses.  How to minimize downtime for public access to our web resources?

Posted on 2011-04-27
Last Modified: 2012-05-11

How do small-mid sized companies switch ISPs, which will include changing static IP blocks, and minimize downtime for public access to our web resources?   We host some of our clients websites.    We can't be off-line for nn hours.  

Via GoDaddy (and others) , we have all the A records pointing to our IIS Server's public IP address.  

When we make the ISP SWITCH, I know we can go to the Domain manager on GoDaddy and repoint the A records, but won't that be like up to a 24 hour delay?    That's too long, our clients will be screaming.

There's got to a be standard way to do this.  

Any how-to comments are appreciated, 500 points.
Question by:JReam
    LVL 8

    Accepted Solution

    Usually GoDaddy is pretty quick when switching A records.  It only takes a while when you're transferring domains and registrars.  If you switch an A record, it should only be about 15 minutes. Maybe less.  But essentially, if you switch IP's, and get new static addresses, there is no other way around it.  I'd recommend switching the records late at night so if anyone encounters issues then there will be less people working.

    Assisted Solution

    Not sure if it's directly relevant, but I've switched clients between third party web hosts which involves changing their IP addresses / DNS records etc.  In general the aim has been to have old and new running in tandem so that you can get the service on the new IP address up and running / tested etc., then swap the A records (without caring how long it takes to propagate - yes, it's often quick, but you can't rely on it) and later take down the old IP address stuff.  Backend links to databases etc. need management so that old and new actually connect to the same data to make it seamless (even if you have a period where performance is degraded), but that shouldn't be too difficult.

    If you're doing this with a single server, can you configure it to use multiple IP addresses (actually this may not be a concern if the servers sit behind firewalls and use private IP addresses)?  You probably need to get someone else to tell you how to do that, but AFAIK IIS (and presumably Apache and others) support multiple IPs.  And configure routers / firewalls / network infrastructure to route traffic through from both IPs to the right places.

    The residual question is what sort of external internet connectivity you have.  I'm sort of assuming that you are hosting all this yourself internally and not using external third party hosting.  So if you are changing ISPs, can you have a period where old and new co-exist?  If you wanted that, would existing external cabling support it (so cost of overlap might not be extortionate)?  Higher end routers should be able to deal with multiple external IP addresses on a single link so what's possible here is at least partly a function of what services the ISPs offer.

    Hope this helps.
    LVL 5

    Assisted Solution

    Go to where your Top Level Domains are hosted and make SURE you change the TTL (refresh time) to the lowest possible settings, this way when you update it with the new IP it will be nearly instant.

    Other then that its going to come down to good planning to switch over everything on the firewall, I would make a checklist and go over it with co-workers.
    LVL 1

    Author Closing Comment

    We ran some timing tests this morning   Godaddy domain manager.   First we lowered the TTL to the minimun of 30mins from 1 hour, then changed the A record.   It took about 1 hour for us to see the switch occur.  

    Thank you very much for your valuable comments.

    Featured Post

    Highfive Gives IT Their Time Back

    Highfive is so simple that setting up every meeting room takes just minutes and every employee will be able to start or join a call from any room with ease. Never be called into a meeting just to get it started again. This is how video conferencing should work!

    Join & Write a Comment

    Meet the world's only “Transparent Cloud™” from Superb Internet Corporation. Now, you can experience firsthand a cloud platform that consistently outperforms Amazon Web Services (AWS), IBM’s Softlayer, and Microsoft’s Azure when it comes to CPU and …
    David Varnum recently wrote up his impressions of PRTG, based on a presentation by my colleague Christian at Tech Field Day at VMworld in Barcelona. Thanks David, for your detailed and honest evaluation!
    Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
    Here's a very brief overview of the methods PRTG Network Monitor ( offers for monitoring bandwidth, to help you decide which methods you´d like to investigate in more detail.  The methods are covered in more detail in o…

    734 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    24 Experts available now in Live!

    Get 1:1 Help Now