Forum Discussion
Deploying Domain Controllers with an Availablility Group
Most Microsoft documentation states to deploy DC's in an availability group for maintenance and failure situations.
The issue is that all the servers in an availability groups all use the same DNS settings, which doesn't work for several well known reasons.
The only solution is to either build another availability group with additional DC's, (Which can add a significant cost to the project) or point the original availability group back to on-prem DC's, thereby negating the reliance on on-prem architecture.
Is there any new guidance for this situation?
6 Replies
- If you have requirement to use different DNS setting for your VMs, create two vnets with different DNS configuration and place your VMs in 2 different Availability Zones on each vnet.
I'm not sure what you mean by 'servers in an availability groups all use the same DNS settings'.
A VM NIC in Azure, by default, inherits its DNS settings from the virtual network. Open the VM nic resource in the Azure portal - DNS servers and you'll see two options:
'Inherit from virtual network' - this is the default setting for a NIC
'Custom' - allows you to use custom DNS settings for that VM NIC
An Availability set works differently than individual VM's. All VM's in an availability set use the same DNS settings. When you change one NIC DNS settings, that setting will propagate to all servers in the Availability Set. If you try to manually change the DNS setting, say in the VM, when the VM reboots, it will inherit the DNS from the Availability set.
This creates an issue specific to DC's where at least one DC will have it's primary DNS pointing to itself, which in not best practice.
I've just run up 2 VMs in an availability set and can change the DNS settings on a single NIC on a VM in the availability set.
