Category: Network

Unable to move failed-over-to-DR databases back to production Site

I recently came across a scenario, where an Exchange environment that had been configured in a Best Practice state had failed over to the DR site due to an extended network outage at the primary production site, and was unable to re-seed back and fail back over.

The environment was configured very similar as described in the Deploy HA documentation by Microsoft, and had it’s DAG configured across two sites:

Stock example showing DR site relationship

Instead of the “Replication” network that is shown in the above graphic, the primary site had a secondary network (subnet 192.168.100.x) where DPM backup services ran on, the DR site did not include a secondary network.

Although the Exchange databases were mounted and running on the DR server infrastructure, the replication state was in a failed state at the primary site. Running a Get-MailboxDatabaseCopyStatus command showed all databases in a status of DisconnectedAndResynchronizing

DisconnectedAndResynchronizing state

All steps attempted to try to re-establish synchronization of the databases failed with various different error messages, even deleting the existing database files and trying to re-seed the databases failed, with most messages pointing to network connectivity issues.

Update-MailboxDatabaseCopy vqmbd06\pcfexch006 -DeleteExistingFiles

Confirm
Are you sure you want to perform this action?
Seeding database copy "VQMBD06\PCFEXCH006".
[Y] Yes  [A] Yes to All  [N] No  [L] No to All  [?] Help (default is "Y"):
The seeding operation failed. Error: An error occurred while performing the seed operation. Error: An error occurred
while communicating with server 'DCExchange'. Error: A socket operation was attempted to an unreachable network
10.50.3.15:64327 [Database: VQMBD06, Server: pcfexch006.xxxxx.com]
    + CategoryInfo          : InvalidOperation: (:) [Update-MailboxDatabaseCopy], SeedInProgressException
    + FullyQualifiedErrorId : [Server=PCFEXCH006,RequestId=e0740b4a-7b94-42f5-b3ad-7ee42632f9c4]
 [FailureCategory=Cmdlet-SeedInProgressException] 2D10AE04,Microsoft.Exchange.Management.SystemConfigurationTasks.UpdateDatabaseCopy
    + PSComputerName        : pcfexch006.xxxxx.com

Looking carefully at the error message, the error says: A socket operation was attempted to an unreachable network 10.50.3.15:64327

Very strange, as when a network test was run, no errors occurred with connecting to that IP and TCP port.

Test-NetConnection -ComputerName DCExchange -Port 64327


ComputerName     : DCExchange
RemoteAddress    : 10.50.3.15
RemotePort       : 64327
InterfaceAlias   : Ethernet
SourceAddress    : 10.50.2.42
TcpTestSucceeded : True

When the test command Test-ReplicationHealth was run, the ClusterNetwork state was in a failed state:

PCFEXCH006      ClusterNetwork             *FAILED*   On server 'PCFEXCH006' there is more than one network interface
                                                      configured for registration in DNS. Only the interface used for
                                                      the MAPI network should be configured for DNS registration.
                                                      Network 'MapiDagNetwork' has more than one network interface for
                                                      server 'pcfexch006'. Correct the physical network configuration
                                                      so that each Mailbox server has exactly one network interface
                                                      for each subnet you intend to use. Then use the
                                                      Set-DatabaseAvailabilityGroup cmdlet with the -DiscoverNetworks
                                                      parameters to reconfigure the database availability group
                                                      networks.
                                                      Subnet '10.50.3.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.3.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.3.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.3.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.3.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '192.168.100.0/24' on network 'MapiDagNetwork' is not Up.
                                                       Current state is 'Misconfigured'.
                                                      Subnet '192.168.100.0/24' on network 'MapiDagNetwork' is not Up.
                                                       Current state is 'Misconfigured'.
                                                      Subnet '192.168.100.0/24' on network 'MapiDagNetwork' is not Up.
                                                       Current state is 'Misconfigured'.
                                                      Subnet '192.168.100.0/24' on network 'MapiDagNetwork' is not Up.
                                                       Current state is 'Misconfigured'.
                                                      Subnet '192.168.100.0/24' on network 'MapiDagNetwork' is not Up.
                                                       Current state is 'Misconfigured'.
                                                      Subnet '10.50.2.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.2.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.2.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.2.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.
                                                      Subnet '10.50.2.0/24' on network 'MapiDagNetwork' is not Up.
                                                      Current state is 'Misconfigured'.

The Failover Cluster Manager was checked, but no errors were found, and the networks in question were “Up”, and in green status.

Looking further at the output of the Test-ReplicationHealth shows that the current state is “Misconfigured”, so let’s see how that replication traffic is configured. The following shows the output of Get-DatabaseAvailabilityGroupNetwork

RunspaceId         : 57e140b2-15ad-4822-9f94-3e1b0d34f491
Name               : MapiDagNetwork
Description        :
Subnets            : {{10.50.3.0/24,Up}, {10.50.2.0/24,Up}}
Interfaces         : {{DCExchange,Up,10.50.3.15}, {pcfexch005,Up,10.50.2.36}, {pcfexch006,Up,10.50.2.42}}
MapiAccessEnabled  : True
ReplicationEnabled : True
IgnoreNetwork      : False
Identity           : VarDAG2016\MapiDagNetwork
IsValid            : True
ObjectState        : New

RunspaceId         : 57e140b2-15ad-4822-9f94-3e1b0d34f491
Name               : ReplicationDagNetwork01
Description        :
Subnets            : {{192.168.100.0/24,Up}}
Interfaces         : {{pcfexch005,Up,192.168.100.218}, {pcfexch006,Up,192.168.100.217}}
MapiAccessEnabled  : False
ReplicationEnabled : True
IgnoreNetwork      : False
Identity           : VarDAG2016\ReplicationDagNetwork01
IsValid            : True
ObjectState        : New

An attempt was done to reset the network state by disabling the automatic configuration and re-enabling it with the following commands:

Set-DatabaseAvailabilityGroup VarDAG2016 -ManualDagNetworkConfiguration $true
Set-DatabaseAvailabilityGroup VarDAG2016 -ManualDagNetworkConfiguration $false

No change, and the seed attempt failed again.

An attempt to remove the Backup network (Here named “ReplicationDagNetwork01“) from the replication traffic was done with the following commands:

Set-DatabaseAvailabilityGroup VarDAG2016 -ManualDagNetworkConfiguration $true

Set-DatabaseAvailabilityGroupNetwork -Identity VarDAG2016\ReplicationDagNetwork01 -ReplicationEnabled:$false

No change was seen, and the seed attempt failed.

Looking further at the what options the command had, the “IgnoreNetwork” option was used:

Set-DatabaseAvailabilityGroup VarDAG2016 -ManualDagNetworkConfiguration $true

Set-DatabaseAvailabilityGroupNetwork -Identity VarDAG2016\ReplicationDagNetwork01 -ReplicationEnabled:$false -IgnoreNetwork:$true

Still no change, so I set back the autoconfiguration with the command:

Set-DatabaseAvailabilityGroup VarDAG2016 -ManualDagNetworkConfiguration $false

Running Get-DatabaseAvailabilityGroupNetwork | fl showed no visible change, but the Site-to-Site tunnel showed a massive uptick in usage, so I ran the Get-MailboxDatabaseCopyStatus command, and it showed all databases that were in a status of DisconnectedAndResynchronizing synchronizing! I retried the reseed process, and it worked!

I’m not sure why the Set-DatabaseAvailabilityGroupNetwork command showed no visible changes, but it’s obvious the changes did occur, that the replication was disabled over the BackupNet (192.168.100.x) and forced over the correct network.

Inside access to external NAT IP services

The corporate office has an environment where there is a separate “guest” network for vendors, visitors, etc. that can use their own devices, to use internet services through Wi-Fi.
Due to the fact some internal services are needed such as joining internal Audio/Video conferences, and access to collaborative services, we had a requirement that access to those services be available through this semi-public network that is “external”, i.e. uses external DNS resolution, but is still “inside” the firewall boundary as shown below.

Access from GuestNet-Diag

To spell it out, we had the following infrastructure:

  • Internal services only accessible from inside the corporate network and internal devices.
  • External services accessible from outside the corporate network.
  • Guest network with external/public DNS resolution.

The requirements are as follows:

  • Internal services accessible externally if secured with boundary extending services, primarily Microsoft Direct Access, or if explicitly approved, Cisco VPN software.
  • Skype for Business availability for Guest Wi-Fi to join conferences and collaboration.
  • SharePoint services (specifically Office Online Server) for collaboration access from Guest Wi-Fi.

Cisco has a good article here: https://www.cisco.com/c/en/us/support/docs/security/asa-5500-x-series-next-generation-firewalls/72273-dns-doctoring-3zones.html to make this process work, the D-NAT methodology was used, but the article can a bit confusing, so I just wanted to explain a couple things to clarify it, and show how the final NAT rules end up looking.

The following are the relevant NAT rules:

Access from GuestNet

  • For the Match Criteria:
    • Source is the Guest network.
    • Destination for the Skype for Business services is the “inside” DMZ interface, as in this case, the DMZ is sandwiched, has an internally facing network, and an externally facing network, or wherever the service resides, as some services are on the “services” network.
    • IP source is the Guest network object.
    • IP destination is the External IP of the service.
  • For the Action:
    • Source is wherever the service resides.
    • Destination is the Internal IP of the service.

I hope this helps clarify the Cisco article.

 

Setting the Network Profile in Windows 2012 or higher

I recently had a non-domain joined edge Windows 2016 machine with two separate NICs that I needed to set different Windows Firewall settings to. Why? For instance, I wanted to allow RDP for the Internal NIC, and not allowing it for the External one, etc. The problem was, the NICs were set with the wrong network profile, the external public facing one was set to Private, and the other was reversed as shown in the following screen capture:

Network Connect profile - 1-1

New with Windows Server 2012 and higher, to change the network profile, PowerShell v4 cmdlets need to be used! Those cmdlets are:

Get-NetConnectionProfile
Set-NetConnectionProfile

Here are the results with the “Get” command:

Network Connect profile - 1

We can see the results are reversed, as the “Internet” connection has the “Private” designation, thus the wrong Windows Firewall profile is assigned to it.

To fix that, we run the “Set” command as shown in the bottom of the capture above, and the correct firewall profile is assigned!

Note: I named the external facing NIC “Public”, and the internal facing one “Private”. You can name it whatever you’d like, and identify it with the -InterfaceAlias property.

Network Connect profile - 1-4

The default profile in Windows Server 2012+ is Public. It automatically changes when you join the server to the Domain. In my instance, I was not joining this server to a Domain, and thus had to set it manually, on top of that, in this instance, the automatic designation was configured incorrectly.