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MX & A records to enable exchange to recieve mail through 2 wan connections

Posted on 2008-10-10
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Last Modified: 2012-05-05
Hi

We're setting up a SBS2003 network using 2 internet connections for redundency
Do we set up reverse DNS on both connections to mail.foo.com and then have both IPs in the main MX record, with the preferred connection getting priority?

I have found these similar links, but they seem to give conflicting answers.

http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_23199359.html
http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/2003_Server/Q_23199359.html
http://www.experts-exchange.com/Networking/Protocols/DNS/Q_23629296.html
http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_23307633.html
http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_22028421.html

So far I have set up a A record pointing to WAN1 and a corresponding MX record, but any info about adding the 2nd WAN connection to this would be greatly appreciated.

thanks

Spotta
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Question by:sp0tta
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Bertling earned 500 total points
ID: 22685971
ok this is my view on it...

you have WAN1 ip adress 195.1.1.1
you have WAN2 ip address 195.2.2.2

your domain is @mydomain.com

you create 2 A records for each wan address

WAN1.mydomain.com = 195.1.1.1
WAN2.mydomain.com - 195.2.2.2

you create these MX records

mydomain.com    MX preference = 10, mail exchanger = WAN1.mydomain.com (makes WAN1 IP address the prefered delivery address)

mydomain.com    MX preference = 20, mail exchanger = WAN2.mydomain.com (backup if WAN1 fails)

so now you have 2 MX records and A records that point to each external IP address.

you now need to port forward or NAT both the external ip addresses 195.1.1.1 and 195.2.2.2 to the internal IP address of the exchange server.

Now we need to setup the RDNS for both WAN1.mydomain.com and WAN2.mydomain.com.

create 2 RDNS records in your DNS:
195.1.1.1 - WAN1.mydomain.com
195.2.2.2 - WAN2.mydomain.com

you can now ping -a 195.1.1.1 and ping -a 192.2.2.2 and this will resolve to the correct external DNS A Record.

now mail can will be delivered to WAN1, if WAN1 failes it will then use WAN2 instead. the external IP addresses for both WAN1 and WAN2 can be resolved to the correct DNS name which is in the MX records.

all will work fine and no RDNS issues.

the only quick change you would need to do is in exchange and change the FQDN in the SMTP virtual server to the live external mx record if wan1.mydomain.com failes for e.g. you would have to change it to WAN2.mydomain.com. But in most cases email wont be rejected if this is wrong.

hope this helps
mike
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Expert Comment

by:Bertling
ID: 22685991
just to add my solution is the same as the one in this post

http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_23307633.html

this is the correct way apart from it seems he missed the other A record when he did his solution.
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Author Closing Comment

by:sp0tta
ID: 31504932
Perfect.

Thank you
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