How to setup a secondary mail server in case the first one goes down?

How to setup a secondary mail server in case the first one goes down?

Post by bzh.. » Thu, 08 Apr 1999 04:00:00



Hi,

We are running an old version sendmail and primary DNS server on Sun
OS 4.1.x. We are going to switch ISP, which force us to change IPs of
this SunOS 4.1.x. We have already connected with our new ISP, while
still mainting connection with old ISP for another  two weeks.. We are
going to change the IPs next week.

There will be a short period that some one will use old IPs to send
e-mail to us due to the DNS cache somewhere. But we want smooth
transition so that no mail gets lost or bounced back to the sender.
What is our best, simple option to achieve this? We have SunOS,
Solaris 2.5 -2.6, Win NT 4.0 and 95 machines.

One option to us seems to be, before we change all machine IP address,
we set up one NT machine to run Exchange Server and to be our
secondary mail server and it is using a new IP address from our new
ISP. We will push our information to let the world know this is our
secondary mail server and in case the first one failed, mail should be
deliver to it. Then after two days, we are going to change all machine
IPs address.

Here I am not sure how could we let world know this machine will be
our secondary mail server? through our DNS server or sendmail.cf?

Should we change our IPs first, then tell internic about the new IP
for our priamry and secondary DNS server? or the other way around?

Thanks

Bing

 
 
 

How to setup a secondary mail server in case the first one goes down?

Post by Robert B. Kast » Fri, 09 Apr 1999 04:00:00



> Here I am not sure how could we let world know this machine will be
> our secondary mail server? through our DNS server or sendmail.cf?

Through the DNS server by having multiple MX records with different
preferences. Take a look at some reference materials like the
excellent "TCP/IP Network Administration" by Craig Hunt and published
by O'Reilly.

Quote:> Should we change our IPs first, then tell internic about the new IP
> for our priamry and secondary DNS server? or the other way around?

Submit the modify to the Internic first. Point to your new DNS server
on the new ISP. (The ISP should also act as your DNS secondary.) On the
new DNS servers, set up your new MX records to point to a mail system
on the new ISP (obviously).

Run both old and new systems until you see little or no email on the
old system. Depending upon your Refresh and TTL values, you should
stop seeing mail after a few days. Once that happens, you can move your
SunOS4 box off the old ISP.

Opinions expressed herein are my own and may not represent those of my employer.

 
 
 

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