Hello,
I have an Exchange 2013 deployment and a LAN/WAN setup, we have many small remote WAN linked offices that can resolve to the Exchange Server's internal IP.
Outlook clients in remote WAN offices work fine as long as the link is UP since the Split Brain DNS for Exchange will resolve the internal clients to the internal IP of the Exchange server, Outlook connects up without issues.
However, in the event of loosing connection to our remote sites, they will no longer be able to resolve to the internal Exchange IP, but they still have a backup public internet that they can use. So should the inter-office connectivity fail we have it setup so clients in remote offices can still browse the internet, etc.
However, their Outlook fails to connect because it has a cached DNS record for our Split Brain Exchange DNS setup and tries to resolve it to its internal IP, instead of refreshing the cache and grabbing the public IP of the Exchange server since now they would be resolving it over the public internet.
Is there anything I can do with my existing configuration to allow the client to pick up the public IP of the Split DNS setup when our inter-office connection is down and the client is no longer able to use the internal IP they have cached for Exchange?
I guess I could lower the TTL on the DNS record to something like 1 minute so it does not cache the DNS record / IP for long? Is this the best approach?