Multiple MX records for the Edge Transport server

17 Oct 2007 4:31 PM

johnny_mango

Hi there,

IÂ´d like to implement my Edge Transport Servers in a high availability
scenario, using 2 x MX records. This question might sound basic, but it has
to be asked.

Will this then require 2 x public IP addresses for each MX, each passing on
port 25 traffic to one specific Edge Transport Server? I imagine that most
firewalls wouldnÂ´t do this kind of load balancing, but that isnÂ´t my area.
Or can I have 1 x MX, pointing to the same host record with 2 different IP
addresses? Either way I canÂ´t see a way to avoid having 2 IP addresses
published.
Now that I think about it, could I have two MX records pointing to two host
records, which point to the same IP, and then have the firewall detect the
original host name to which the request was sent and partition it out to the
respective Edge Transport server?

Thanks for any advice you can give.

17 Oct 2007 10:14 PM

Bharat Suneja [MVP]

Whether you use DNS round-robin (one MX point to an A record
server.domain.com, two A records pointing to 2 diff external IP addresses),
or use the in-built MX capability of load-balancing (2 MX records with same
preference pointing to 2 A records mapped to diff IP addresses) or
"fail-over" (different preference values on both MX), you need 2 external IP
addresses.

The other option is to use something like ISA, Windows Server's NLB, or a
hardware load-balancer. This allows you to get by with one IP address (a
"vritual IP address", so to speak) that any of the above listen on and
load-balance to the 2 or more internal IPs.

--
Bharat Suneja
MVP - Exchange
www.zenprise.com
NEW blog location:
exchangepedia.com/blog
----------------------------------------------

Show quote

"johnny_mango" <johnnyma***@discussions.microsoft.com> wrote in message
news:86226CAC-F618-49D7-BE61-C0F79C320AAE@microsoft.com...
> Hi there,
>
> IÂ´d like to implement my Edge Transport Servers in a high availability
> scenario, using 2 x MX records. This question might sound basic, but it
> has
> to be asked.
>
> Will this then require 2 x public IP addresses for each MX, each passing
> on
> port 25 traffic to one specific Edge Transport Server? I imagine that most
> firewalls wouldnÂ´t do this kind of load balancing, but that isnÂ´t my area.
> Or can I have 1 x MX, pointing to the same host record with 2 different IP
> addresses? Either way I canÂ´t see a way to avoid having 2 IP addresses
> published.
> Now that I think about it, could I have two MX records pointing to two
> host
> records, which point to the same IP, and then have the firewall detect the
> original host name to which the request was sent and partition it out to
> the
> respective Edge Transport server?
>
> Thanks for any advice you can give.