Good advice on the DNS propagation. However, the reality of the 'net is such that some largish ISP networks do not respect TTLs and take a week to propagate through their caching. Ugly. So, the "could also" needs to be a "should also" do one of several things to avoid losing email due to poor cache hygiene:
- NAT/Forward TCP/IP connections from old to new,
- setup james on old machine (i.e., former IP Address) to use remote delivery to the other machine's IP address,
- setup different MTA on old machine (address) to relay to new machine,
- etc.



(Part of the etc. is my solution to the same problem: sharing the database with two James instances over a VPN/SSH/SSL tunnel)


Robert Taylor

Danny Angus wrote:





If you have control over your dns entries reduce the TTL of your primary A
record to half an hour or so, then it should propogate through four levels
of cache within two hours.

You could also use a packet filtering firewall to forward all the TCP/IP
traffic on certain ports to another machine (eg iptables on linux or a
standalone GNAT firewall)
Even if you don't care about security this scenario is a real good reason
for having a firewall/router as your front line.

d.


|---------+----------------------------> | | "J Malcolm" | | | <[EMAIL PROTECTED]| | | ms.com> | | | | | | 01/04/2004 09:14 | | | PM | | | Please respond to| | | "James Users | | | List" | | | | |---------+----------------------------> >---------------------------------------------------------------------------------------------------------------| | | | To: "James Users List" <[EMAIL PROTECTED]> | | cc: | | Subject: Migrating Server to Another Box/IP | >---------------------------------------------------------------------------------------------------------------|




I am planning to move my domains to another box and another IP address. Iâm well aware of the propagation delays when a domainâs IP address changes. I need to minimize the disruption to my users and obviously not lose any mail in the process. Is there any âbest practicesâ for how to do this?

      Details:  when I actually throw the switch, some mail will begin
      going to the new box fairly quickly while some mail from servers
      using a cached DNS entry for the domain will continue to send to the
      old box until the cached address expires, which could be a couple of
      days.

      Likewise, some usersâ mail program will almost immediately start
      going to the new box while others may stay on the old box for a
      couple of days.

      So the question isâ  is the right answer to just let whatever happens
      happen for a couple of days, and then when the dust settles reprocess
      any leftover mail on the old server to get it routed to the new
      server?  The obvious problem with this is the potential for mail that
      wonât be seen for couple of days.  Is there a tried and true better
      way.

Thanks.

Jerry


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