Question

Sonicwall, dual ISPs and a single email server

Asked by: lmkandia

We are setting up a NSA 240 with dual isp connections.
Failover is set for basic active/passive failover.
Ie. one ISP fails, the other takes over within a minute.
Works great for web traffic.  Nice and seamless.
But we would also like email to keep working as well.

We have an Exchange 2003 server on the inside.
Sending mail should not be a problem.
We just need to make sure that a reverse DNS entry is created at the ISP.
Its receiving it.

We have all incoming mail handled by a 3rd party anti-spam service.
Therefore the MX records are pointed at the 3rd party anti-spam service.

Once the 3rd party anti-spam service massages the email, it sends it to the Exchange server.  The facility to do this, is a simple IP address entry for the applicable domain.  Currently only the 1st ISP's static IP is in there.  We plan to add the 2nd ISP's static ip address in there as well.

So here is the question.  Is it valid to have 2 static ip addresses from different ISPs pointed at the same Exchange email server?  Both technically and RFC wise?

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Asked On
2009-10-30 at 08:33:40ID24858397
Tags

exchange 2003

,

sonicwall

,

dual isp

Topics

Network Software Firewalls

,

Exchange Email Server

,

Simple Mail Transfer Protocol (SMTP)

Participating Experts
1
Points
500
Comments
7

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Answers

 

by: LingerLongerPosted on 2009-10-30 at 09:18:55ID: 25704444

It's fine to do that, but you should only do it if you can ensure the Spam Service can order them. That is, all mail will be sent to the 1st ISP unless it cannot connect to it, then it would send to the 2nd ISP. Otherwise, mail may fail, since the Active/Passive failover configuration will not let mail through the 2nd ISP link if the 1st ISP link is functional.

 

by: lmkandiaPosted on 2009-10-30 at 09:20:52ID: 25704465

Would Round Robin work any better?
Should we create a "second" public server using the wizard and point it to the 2nd Wan IP?

 

by: LingerLongerPosted on 2009-10-30 at 09:24:27ID: 25704509

It's up to you. I prefer to keep a primary IP for email, so I know where it's typically going, and where to track from if there are issues.
Of course, larger companies do exactly that, and have multiple servers/connections receiving the mail, so the multiple paths in method could work just as well.

 

by: lmkandiaPosted on 2009-12-16 at 07:41:44ID: 26063408

Please don't close this question.  About to test the solution this weekend.

20120131-EE-VQP-002

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