Re: How to do NAT OUT-to-OUT to minimize downtime

Discussion in 'Cisco' started by bod43, Apr 9, 2009.

  1. bod43

    bod43 Guest

    On 9 Apr, 16:18, "Elia Spadoni" <> wrote:
    >     Hello
    > I have this problem:
    >
    > C1721 with 12.4(21) ADVSEC
    > Atm0.1 point-to-point
    > loopback0 1.1.1.2/29 (public wan IP) on this interface I make NAT
    > eth0 LAN 172.16.0.0/27
    >
    > Actually I have a mail server on the lan on 172.16.0.4 - I have one static
    > nat one-to-one 1.1.1.4 (public) to 172.16.0.4 (private)
    >
    > Since I am about to move the mailserver from the public IP 1.1.1.4 to
    > 9.9.9.9 (on a different phisical location) I will change the dns name
    > according to the new ip.
    >
    > At the same time I would like to minimize downtime, redirecting allthe
    > packet arriving on the router to 1.1.1.4:25 , and I would like to
    > transparently redirect them to 9.9.9.9:25 (so i would like to do public -
    > to - public NAT)


    I would think so.

    See my recent post regarding NAT on a stick.

    However, I would question the value of that approach.
    Why not simply add an additional MX record well in
    advance of your desired switchover.
    When you are ready, turn on access to the new server and
    turn off the old one.

    Done.

    for example:-

    gmail have 5 MX records and mail senders will try them in
    order of priority 5, 10, ..... until they find one that works.
    You can do the same.

    My DNS server addresses have been obscured.

    C:\nslookup
    Default Server: xxxx.com
    Address: xxx.xxx.xxx.xxx

    > set type=mx
    > gmail.com

    Server: xxx.com
    Address: xxx.xxx.xxx.xxx

    Non-authoritative answer:
    gmail.com MX preference = 5, mail exchanger =
    gmail-smtp-in.l.google.com
    gmail.com MX preference = 10, mail exchanger =
    alt1.gmail-smtp-in.l.google.com
    gmail.com MX preference = 20, mail exchanger =
    alt2.gmail-smtp-in.l.google.com
    gmail.com MX preference = 30, mail exchanger =
    alt3.gmail-smtp-in.l.google.com
    gmail.com MX preference = 40, mail exchanger =
    alt4.gmail-smtp-in.l.google.com

    gmail-smtp-in.l.google.com internet address =
    209.85.219.57
    alt1.gmail-smtp-in.l.google.com internet address =
    72.14.221.27
    alt2.gmail-smtp-in.l.google.com internet address =
    209.85.217.56
    alt3.gmail-smtp-in.l.google.com internet address =
    209.85.143.114
    alt4.gmail-smtp-in.l.google.com internet address =
    209.85.199.27
    >
    bod43, Apr 9, 2009
    #1
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  2. bod43

    bod43 Guest

    On 9 Apr, 22:40, "Elia Spadoni" <> wrote:
    > Hello
    > thank you for your prompt answer.
    >
    > The problem is that the MX10 (first mx) is also the SMTP and POP3 server...


    Could you turn off inbound SMTP? I thought that was
    what you wanted to do. Turn it off on the server - somehow
    maybe, or block incomming TCP SYN-but-not-ACK.

    The NAT thing might work:)
    bod43, Apr 9, 2009
    #2
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