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

Question

HelloI have this problem:C1721 with 12.4(21) ADVSECAtm0.1 point-to-pointloopback0 1.1.1.2/29 (public wan IP) on this interface I make NATeth0 LAN 172.16.0.0/27Actually 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

bod43 · Accepted Answer

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 inadvance of your desired switchover.When you are ready, turn on access to the new server andturn off the old one.Done.for example:-gmail have 5 MX records and mail senders will try them inorder of priority 5, 10, ..... until they find one that works.You can do the same.My DNS server addresses have been obscured.C:slookupDefault Server:  Address:  xxx.xxx.xxx.xxxServer:  Address:  xxx.xxx.xxx.xxxNon-authoritative answer:       MX preference =3D 5, mail exchanger =3D         MX preference =3D 10, mail exchanger =3D         MX preference =3D 20, mail exchanger =3D         MX preference =3D 30, mail exchanger =3D         MX preference =3D 40, mail exchanger =3D        internet address =3D  209.85.219.57 internet address =3D  72.14.221.27 internet address =3D  209.85.217.56 internet address =3D  209.85.143.114 internet address =3D...

Elia Spadoni · Answer

Hellothank you for your prompt answer.The problem is that the MX10 (first mx) is also the SMTP and POP3 server...

bod43 · Answer

Could you turn off inbound SMTP? I thought that waswhat you wanted to do. Turn it off on the server - somehowmaybe, or block incomming TCP SYN-but-not-ACK.The NAT thing might work:)

Elia Spadoni · Answer

HelloI 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:

Elia Spadoni · Answer

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.

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

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