Our cable company is forcing a change to our static IP

Discussion in 'Windows Small Business Server' started by Rob C, Aug 28, 2007.

  1. Rob C

    Rob C Guest

    SBS2003 SP2 R2 standard
    Static external IP/ DNS routed emails

    They have bought a new block and are giving the old block back - not good...

    So here is the possible issue:

    I want to try and seemlessly change to new IP without interrupting email flow.
    Easy to change the IP with the domain registra and easy to change our
    firewall router, but there is the 24 hour or so wait before the domain info

    I dint think I can add multiple external IPs to our firewall router.

    We subscribe to a backup MX service so emails inbound will be stored.

    What would be the best method to go about this without causing any hiccups
    in mail flow and preferably keep everything working?

    Many thanks for your input.
    Rob C, Aug 28, 2007
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  2. I'd do this - go into your DNS settings now and change the TTL on the
    existing records to one hour. Hopefully your Internet provider is giving
    you a specific time they're going to make the change. I would go in and
    change the IP on the A record an hour or two before they cut you over to the
    new IP. That way, by the time you change, the new IP should have propagated
    throughout the DNS system, so messages will no longer be going to the old
    IP. Messages to the new IP will be failing until they cut you over, but
    that will be well within the time that the sending servers will continue
    trying to deliver the messages.

    I just went through the same thing, and didn't get any complaints from
    senders, although I did alert my users that there could be e-mail problems
    for a couple of hours that day.
    Dave Nickason [SBS MVP], Aug 28, 2007
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  3. Rob C

    Jeff Teel Guest

    When you find out what your new IP address will be add an MX record and an
    A record for DNS record for your domain.
    mail.yourdomain.com. A IN 12400 xxx.xxx.xxx.xxx (This
    would be current IP address which would be looked at first)
    mail2.yourdomain.com. A IN 12400 xxx.xxx.xxx.xxx (This
    would be new IP address which would be looked at second)
    yourdomain.com. MX IN 12400 mail.yourdomain.com.
    [Preference = 10]
    yourdomain.com. MX IN 12400 mail2.yourdomain.com.
    [Preference = 20]

    Make your backup MX record that points to a different mail server the last
    mail server that DNS looks for for example [Preference = 30].

    The transition for mail would be seemless with this configration. You would
    need to adjust your A record for your domain name to point to the new IP
    address so you could access Outlook Web Access and Remote Web Workplace.

    Jeff Teel, Aug 28, 2007
  4. Rob C

    SBS Rocker Guest

    Hi Jeff,
    I like your idea as it does seem less "painful". I am preparing for a whole
    office relocation move. Nothing to serious just moving a few floors up.
    However as long as we are going to move the boss has decided to switch over
    to a new ISP and a T1 line (finally!!). We use a different mail provider and
    will be keeping them. So I'm in the thinking process of putting together the
    "game Plan". Here's my current configuration and preliminary plan.

    SBS 2003 Premium SP1
    Exchange 2003 SP2
    ISA 2004 SP2 (dual NIC of course)

    We host our own Exchange SMTP server. Currently our mail provider (also our
    DNS host) we use them for backup. So are MX and A records point to...

    A records
    companyname.com / resolves to external website
    mail.companyname.com / resolves to external IP address

    We also have a registered FQDN gocompanyname.com / resolves to external IP

    MX records
    companyname.com / resolves to inbound.mailprovider.com / Priority (5) <---
    comapnyname.com / resolves to mail.companyname.com / Priority (1)

    So with a new ISP we will have the new IP address and router installed in
    the new suite prior to the official move date. I plan on doing handling the
    DNS switch the day before we do the actual move. Getting emails to clients
    weekends will not be an issue. So I'm thinking and correct me if I'm wrong
    is that all I have to do is ....

    1. Change my A records to point to the new external IP
    2. Add a new MX record for mail.companyname.com and give it a 10 priority.

    On move day after we get the hardware going.........
    1. Change the IP records on the server
    2. Rerun the CEICW. <-- Will this change my HOST A record on the SBS DNS?
    3. I do use a Citrix server and NAT so I will need to edit my ISA rule on
    that and also rerun altaddr on the citrix server.

    Did I miss anything?


    SBS Rocker, Aug 28, 2007
  5. Rob C

    Rob C Guest

    Thanks both for the invaluable info.
    I can now see 2 methods of getting around this problem.


    Rob C, Aug 29, 2007
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