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

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)

Is possibile on the CISCO 12.4 IOS ?

thank you

Reply to
Elia Spadoni
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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

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

Non-authoritative answer: gmail.com MX preference =3D 5, mail exchanger =3D gmail-smtp-in.l.google.com gmail.com MX preference =3D 10, mail exchanger =3D alt1.gmail-smtp-in.l.google.com gmail.com MX preference =3D 20, mail exchanger =3D alt2.gmail-smtp-in.l.google.com gmail.com MX preference =3D 30, mail exchanger =3D alt3.gmail-smtp-in.l.google.com gmail.com MX preference =3D 40, mail exchanger =3D alt4.gmail-smtp-in.l.google.com

gmail-smtp-in.l.google.com internet address =3D 209.85.219.57 alt1.gmail-smtp-in.l.google.com internet address =3D 72.14.221.27 alt2.gmail-smtp-in.l.google.com internet address =3D 209.85.217.56 alt3.gmail-smtp-in.l.google.com internet address =3D 209.85.143.114 alt4.gmail-smtp-in.l.google.com internet address =3D 209.85.199.27

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Reply to
bod43

Hello thank you for your prompt answer.

The problem is that the MX10 (first mx) is also the SMTP and POP3 server...

Reply to
Elia Spadoni

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:)

Reply to
bod43

Hello I need to make the migration of the mailserver in the most painless way.

I switch off the old server and turn on the new one, but then I need immediately the NAT...

"bod43" ha scritto nel messaggio news: snipped-for-privacy@v6g2000vbb.googlegroups.com...

Reply to
Elia Spadoni

I have solved with an app from analogx named port-forward installed on the server. I will keep the server on till the dns has changed.

Reply to
Elia Spadoni

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