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How to add MX record with TWO seperate ISP providers?

    Question

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    At one of our offices we have a single Exchange server thats connected to our Cable internet provider. We are planning to add a T1 line as a Backup line just in case our CAble internet goes down, the T1 will take over.

    Question ONE : I went on our DNS providers site, I currently see our Mail1.domain.com with pref 10(cable).  So I added an additional one for T1 and called it Mail2.domain.com pref 20(T1).  So now I assume if the Cable goes down, users PC's will query for our second mx record which will be Mail2.domain.com.  Does this seem right?

    Question TWO: My only problem is what happens to users who use external OWA. They are currently setup to always type in http://Mail1.domain.com/exchange.  if the cable goes down, they won't know about it and will continue to type in Mail1.domain.com/exchange.  Is their a way to assign a single host name that can be redundant for OWA use too.  for example a name like OWAMail.Domain.com and if the Cable goes down and switches to T1 the name OWAMail host name won't change, but the IP will.  anyway to implement this?

    Monday, July 25, 2011 12:32 AM

All replies

  • ONE:  Why do you think users' PCs will use MX records?  MX records are used for mail routing, generally not by e-mail client software.  SMTP servers will usually try multiple MX records, so that's one method to ensure mail delivery.

    TWO:  You can tell them to modify the hosts file in their PCs, but I'd be surprised if Outlook will try one then try the other if the first doesn't respond.  But I've never tested that.

     


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Monday, July 25, 2011 2:55 AM
  • Anyone else out there with two ISP's(redundancy) that host Exchange server?  How did you implement your DNS records to switch IP's for same Host Record name i.e.

    For example, our ISPS IP's are are follows

    ISP-Neptune - IP: 1.1.1.1  DNS host is OWA1.domain.com

    ISP-Jupitor - IP: 2.2.2.2   DNS host is OWA2,domain.com

    So right now all our users know to type in owa1.domain.com.  but if ISP-Neptune goes down it will automatically switch to ISP-Jupitor with host record of owa2.domain.com. however the problem is our users won't know that our ISP switched to our redundant ISP-Jupitor.  So any other methods to use a consistant HOST record name and have the IP's switched on that one name?  maybe a virtual host record name where whatever the IP changed to the name remains the same for our users. 

     

     

    Monday, July 25, 2011 1:30 PM
  • typically what you are asking for is done with a device designed to use 2 isp's such as an f5 or radware system.  Those usually involve setting up an NS record for your host instead of an A and MX record. When someone outside looks for the ip, the ns record references the radware/f5 device which changes the dns entry base don which isp to use
    • Proposed as answer by Pantherfan Monday, August 01, 2011 1:21 PM
    Monday, July 25, 2011 2:17 PM
  • would the IP changes be reflected in seconds or in minutes until DNS propogates.  So for example if it fails over to the second ISP, would outside users have to wait until DNS changes those records?
    Monday, July 25, 2011 2:30 PM
  • our radware unit actually picked which link to use based on utilization and would hand out whichever dns entry responded fastest. The radware unit actually has both IP's at all time, it just picks which to send to the external connection instantaneously. Externally the records all point at the radware unit (the isp just has ns records for mail.domain.com for instance). So no replication needed to the internet
    • Proposed as answer by Pantherfan Monday, August 01, 2011 1:21 PM
    Monday, July 25, 2011 2:34 PM
  • thanks for the infoz.  Would that be the Radware LinkProof model? 
    Monday, July 25, 2011 3:19 PM
  • Hi Joel,

    You can configure MX record with Priority/Cost like Mail1.domain.com  - 10.0.0.1 cost 10 your current Server IP

    and then another record Mail2.domain.com 10.0.0.2 cost 20 point to your another server IP.

    This configuration needs to be done at ISP end.

    So incase 10.0.0.1 goes down then mail will reach to you by 10.0.0.2.

    Thanks

     


    Mihir Nayak
    Monday, July 25, 2011 3:36 PM
  • But that won't do anything for clients.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Tuesday, July 26, 2011 5:46 AM
  • That's generally done with a load balancer.  Your idea is lower cost and I don't think it will work like you want it to work.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Tuesday, July 26, 2011 5:47 AM
  • yes, i was referencing the linkproof from radware.  That would allow you to switch inbound/outbound connections between isp's as needed. I hear that f5 makes an even better unit than the linkproof, but i havent used that one.
    • Proposed as answer by Pantherfan Monday, August 01, 2011 1:20 PM
    Tuesday, July 26, 2011 12:07 PM
  • For your question under b) have a look at www.dnsmadeeasy.com.

    I have used the DNS Failover feature for a website, and it worked great. It might work for A records of your webmail, as well. You register your A record with same name (ex. webmail.domain.com), and two different IP addresses. What is does is that it hides one of the IP addresses as long as a primary one is up. Once primary one is down, it changes automatically with the second one. You can put very low TTL. In my case, I have tested several times, and second IP came online after 5 minutes ( I guess 5 minutes are very little if you don't expect to have regular problems with your ISP.


    alfa21
    Tuesday, July 26, 2011 12:14 PM
  • This is the exact method I was using.  basically have one Host record, one points to IP 1.1.1.1 and the other hidden points to IP: 2.2.2.2  it swings the IP's out with the SAME host record name should the primary Internet Service go down.  The problem with this is the lowest TTL one can set is about 20 minutes.  The other problem is some DNS servers Cache these kinds of records far more than 20 minutes so even though you might have a TTL setting of 20 minutes, the other ISP providers in the world would increment this to be 240 minutes for example causing all sorts of other issues.

    What I really want is an immediate solution, one where if the primary ISP goes down, it switches to the secondary IP while keeping the same dns Host Record Name the same.  I think the F5 solution might be the way to go. 

    Tuesday, July 26, 2011 5:01 PM
  • There are less costly solutions than F5, like KEMP Technologies.
    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Tuesday, July 26, 2011 7:18 PM
  • We have Kemp at our shop, and we use together with Exchange 2010, but I'm not sure they have such capability. However, it is easy to contact them, they have very helpful support, and they will give you a virtual box to try for a period of time before deciding to purchase.
    alfa21
    Tuesday, July 26, 2011 7:49 PM
  • This is the exact method I was using.  basically have one Host record, one points to IP 1.1.1.1 and the other hidden points to IP: 2.2.2.2  it swings the IP's out with the SAME host record name should the primary Internet Service go down.  The problem with this is the lowest TTL one can set is about 20 minutes.  The other problem is some DNS servers Cache these kinds of records far more than 20 minutes so even though you might have a TTL setting of 20 minutes, the other ISP providers in the world would increment this to be 240 minutes for example causing all sorts of other issues.

    What I really want is an immediate solution, one where if the primary ISP goes down, it switches to the secondary IP while keeping the same dns Host Record Name the same.  I think the F5 solution might be the way to go. 

    Check to see if your ISP Providers provide BGP Routing.  This way both providers announce routes to your servers and if one ISP goes offline the second route is already in place...

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    Tuesday, July 26, 2011 10:53 PM
  • Hi alfa21,

     

    Any updates on this issue?

     

    Here is a similar thread, hope can give you some help:

     

    How to set MX pointer using multiple Internet Connection and multiple IP addresses

    http://social.technet.microsoft.com/Forums/en-US/exchange2010/thread/7d712e83-9e78-445b-8f2a-b123a0cfdfcc

     

    Thanks,

     

    Evan

    Sunday, July 31, 2011 5:21 AM
    Moderator