We have 2 ISPs. Both ISPs are currently being used for separate networks and separate mail servers.
Our corporate internet uses Cox Communications and routes through our Firebox XTM 505. Our corporate Exchange 2007 server routes outbound emails through the external interface of our XTM 505. Inbound emails are routed through MXLogic (McAfee) SPAM and the MX records for this config are hosted on the Cox DNS servers.
Our contractor's network has a single server used for email (Kerio Connect) and a web server. It uses Time Warner for ISP and routes email (inbound and outbound) through the external interface of a Firebox x20e. The MX records for this mail server are hosted on the Time Warner DNS servers.
We would like to use the MultiWAN failover option on the Firebox XTM 505 and utilize the two ISPs we currently have however I have a few questions and concerns.
- Is it possible to keep the two networks separate and operational as separate networks utilizing MultiWAN fail-over or will we need a third ISP to achieve the fail-over we are looking for? It seems that if MultiWAN fail-over is used, one ISP will become idle until needed.
- As far as MX records and email routing (correct me if I am wrong) I will need to have the MX records hosted on the second ISP with a preference of 20. Current MX records are a preference of 10.
- What is the best way to achieve Redundant DNS providing the scenario we currently have.