DHCP, Cable modem, and DNS pointers

Posted on 2004-08-19
Last Modified: 2010-04-11
I have a cable modem connection through which I host an Exchange Server.  My conneciton IP address is served to me through DHCP which, for the most part, remains static.  My domain is registered with Network Solutions and for my MX record I'm using as a pointer.  This works great right now but to make it work I had to statically map a number of A records within Network Solutions to my current DHCP address.  Obvisiously this will cause a problem and a loss of email when my IP address changes and I have to wait for DNS to catch up.  Is there a way around chaning the static records everytime my IP changes?
Question by:sunny10
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Expert Comment

ID: 11850012

you better use IP reservation in DHCP for your exchange server then everytime same IP would be assigned to your exchange and you don't have any problem with it.


Author Comment

ID: 11851277
? My MX record points to my gateway which is my cable modem.  The address assigned to it is dynamic.  My exchange server sits on my internal network which is privately addressed, hardcoding the exchange's IP address (which it already is) won't help my case.

Expert Comment

ID: 11851303
Have you asked your cable provider if they could set your ip as static, its not difficult for them to do. Seems the best option to me.

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Expert Comment

ID: 11851569

only option is to get static IP address (by DHCP reservation) for your exchange (MX record) and your internet service provider(ISP) can do it without any problem. I am very sure they do this for others. solution is just a phone call away to your ISP :)


Expert Comment

ID: 11853173
in the case your isp doesn't do this. a quick fix is to set a batch file or script to run ipconfig /renew everyday. this way it forces the dhcp everyday and every 12 hours to renew and check for the same ip. this will be enough IF the isp doesn't change your ip. this is just to make sure some other comp on the network ends up taking your ip. but this only will work if your dhcp client is online 24/7

Expert Comment

ID: 11884932
You are using a dyndns hostname for your MX record?  That should work.  Why did you have to statically map some A records?  All network solutions should need to know is your dyndns hostname?  Then when your IP changes, dyndns updates it.  And that happens pretty fast.


Expert Comment

ID: 11889204
no luck guys, if they change yourr ip address you will have to get the hold of network solutions, and change your mx recer, then it will take 24 hours to replicate this address throuhout the world. Cable it is not a good solution for the exchange server. try to find static ip soluton for your network maybe DSL.


Accepted Solution

brian_appliedcpu earned 125 total points
ID: 11909216
Why don't you just sign up for a Secondary Mail Catch-all....D.B.A. Mail Gateway.
We have two just in case we go down or or secondary goes down.  then when we do come back up the mail is automatically delivered to us.
Sitelutions offers one for less than $20 / yr.


Expert Comment

ID: 12161188
You'll probably not lose any mail anyway - typically SMTP servers try resending for around five days, which is usually longer than the DNS should take to propagate.

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