Exchange 2010–2016: Site Switchover and Site Switchback with DAC

  • One forest,
  • Two AD Sites, EWR (DR) and LGA (Primary)
  • Five multiple role Exchange 2010 SP3 UR6 servers, four in the LGA (Primary) site and one in the EWR (DR) site
  • Single DAG spanning both sites
  • Namespace in the LGA site (primary, so ExternalURL and InternalURL) is and EWR site (DR — non internet facing, so InternalURL only) is
  • Only the Primary (LGA) site is internet facing
  • Stop the clustering services
  • Evict the servers within the failed site
Stop-DatabaseAvailabilityGroup –Identity DAG –ActiveDirectorySite LGA –ConfigurationOnly:$TRUE
Get-DatabaseAvailabilityGroup | FL Name, StoppedMailboxServers, StartedMailboxServers
Restore-DatabaseAvailabilityGroup DAG01 –ActiveDirectorySite EWR
Import-Module FailoverClusteringGet-ClusterGroup –Cluster DAG01
  • Change the source server for the Send connector to include the HUB transport servers in the surviving, DR site
  • Change the Receive connector on the surviving HUB transport server to accept emails from your source (usually either a NAT from the internet, or a smarthost device)
  • Depending on how you have the NAT and / or Smarthost setup you may need to change DNS records (MX records and TXT records)
Get-ClientAccessServer EWR-EXCH01 | Select AutoDiscoverInternalURI
Set-ClientAccessServer EWR-EXCH01 –AutoDiscoverInternalUri https://<value>
  • Ensure that your boundary device (device sitting between the internet and the LAN) is configured to pass TCP 443 to your internal endpoint (if you have a single CAS like I do, then it’s that. If you have a hardware load balancer you point the boundary device to the hardware load balancer)
  • Change your internal and external DNS A records (if required) to point to the EWR endpoint for client access (usually either a CAS or a Hardware load balancer internally, externally will be your boundary device — either a firewall or reverse proxy)
Start-DatabaseAvailabilityGroup DAG –ActiveDirectorySite LGA
  • Get-DatabaseAvailabilityGroup | FL Name, StartedMailboxServers to ensure the servers did start
  • Import the Failover Clusters module into Exchange Management shell and run the Get-ClusterNode and Get-ClusterGroup commands. Cluster Group should show as online and Cluster Node should show all Exchange servers as up
  • Check your mailbox database copies (if your CI state is showing as failed give it a few minutes, the CI troubleshooter will usually fix this)
  • Adam F




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Adam Farage

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IT Leader, and Subject Matter Expert around Digital Workplace and Microsoft 365.

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