MX Preference question

[jonnyboydps]

Hi Everyone,

I have an existing MX preference of 10 that points to a public IP address, lets say it's 195.x.x.1

I would like to create an additional MX preference of 15 that points to the same IP address.

Is this good practice?

The reason for this is the MX 10 is for an Exchange 5.5 server. The MX 15 will be for an Exchange 2003 server. I am going to be upgrading a domain from 5.5 to 2003 and when the time comes, want to adjust my firewall NAT to point the internal address of the new 2003 server to the 195.x.x.1 address.

Hope that makes sense,

Thanks

Jon

 

[Serbtastic]

Having 2 MX records that point to the same IP address is pointless. The reason you'd have multiple MX records is so if the first mail server at the first priority IP is unreachable then mail gets directed to the second IP.

 

[GlenJohnson]

Jon, you're talking about 2 different machines, correct? They will have the same ip, but one will be shut down when the other comes up?

Glen A. Johnson
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[ChrisAC]

Jon,

If you are just going to change your firewall settings to map the global IP address to a different internal server then you do not need to do anything to your MX records. Having a second one with the same IP address as the first is completely pointless.

Just map the global IP to the new internal IP on the firewall. As far as the world is concerned, it will be the same mail server.

Chris.

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Chris A.C, CCNA, CCSA
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[jonnyboydps]

Guys, thanks for your feedback.

In response to Glen's question, each MX preference points to a different server, 10 points to the existing server and 15 will point to the new server.

The existing MX points to an IP and a hostname.
Does it matter that the new server will have a different hostname but the same public IP address? Do all mail servers use IP to send and recieve mail and not hostnames?

Jon

 

[ChrisAC]

each MX preference points to a different server, 10 points to the existing server and 15 will point to the new server.

Really? That's not what you said!

I would like to create an additional MX preference of 15 that points to the same IP address.

All MX records MUST point to a hostname and not an IP address. The hostname then has an A record that maps it to an IP address.

So, will the new server be on a different public IP address or just a different private IP address? If it's just a different private IP address that you will map to the existing public address then you don't need to do anything with DNS.

If you are changing the public IP address then a better approach would be to just reduce the TTL on the domain before you change the public IP so that propagation occurs quickly.

Chris.

**********************
Chris A.C, CCNA, CCSA
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