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Learn about Active Directory and Various Azure Services

Archives for January 2018

Azure Accelerated Networking

Last Updated on January 23, 2018 by Dishan M. Francis

Early January Microsoft announced general availability of Azure Accelerated Networking (AN). It is now available for all the regions. This will improve the VM’s performance as its offloading software-define networking from CPU to FPGA-based SmartNICs. To make it more interesting, it can provide up to 30Gbps networking throughput without any additional charge. 

How it works? 

If you worked with Hyper-V clusters, System Center virtualization manager (SCVMM) you may probably aware how virtual switches works. It works as a middle man between virtual machines and physical network to provide greater control over “Communication”. It allows to move workloads between physical hosts, control traffic and isolation using policies, flexible hardware upgrades etc. Azure also uses virtual switches similar to hyper-v. 

accelerated-networking
Image source: https://docs.microsoft.com/en-us/azure/virtual-network/media/create-vm-accelerated-networking/accelerated-networking.png 
 
You also can read more about it using this link. 
 
As you can see in the above image without accelerate networking, traffic always need to pass through the virtual switch and physical hosts before it reaches the physical switch. When Accelerated networking in place, network traffic is directly handled by physical switch by bypassing host and the virtual switch. All the policies you used with virtual switches now can offload to hardware. As it removes the dependency of host to process the packet, we will be able to see lower latency. If there is no AN, Virtual switch process all the policies applying to network traffic. Since it is software based of cause it is need to handle by CPU. But the performance of it depend on the CPU utilization and number of policies. With AN, policies will no longer rely on CPU and it handle by the dedicated hardware. This will reduce jitter. 
 
Limitations 
 
There are few limitations applying to this feature. 
 
1. Can’t use with existing VMs – In order to use AN features, Virtual machines must be created with Accelerated Networking enabled. This feature cannot enable in existing VMs. 
2. A NIC with AN cannot attached to an existing VM –  A NIC with AN enabled only can attached during the VM creation process. It is not possible to attach it to existing VM. 
3. Azure Resource Manager only – This feature only can use with ARM. It can’t use in classic portal. 
 
Supported VM Instances 
 
Azure Accelerated Networking is supported on D/DSv2, D/DSv3, E/ESv3, F/Fs/Fsv2, and Ms/Mms Azure VM series. 

Supported Operating Systems
 
Azure Accelerated Networking is supported on both Linux and Windows operating systems such as, 
 
• Windows Server 2016
• Windows Server 2012R2
• Ubuntu 16.04
• Red Hat Enterprise Linux 7.4
• CentOS 7.4
• SUSE Linux Enterprise Server 12 SP3
 
This marks the end of this blog post. Hope this was useful. In next post I will demonstrate how to create VM with AN feature. If you have any questions feel free to contact me on rebeladm@live.com also follow me on twitter @rebeladm to get updates about new blog posts.

Understanding Group Policy Conflicts

Last Updated on January 20, 2018 by Dishan M. Francis

In an organization, there can be many group policies in used. Sometime multiple policies may target same thing. In that case it is important to understand which policy going to win. Group Polices precedence order LSDOU and Group Policy Inheritance decides which policy will win in Active Directory structure.  Let’s look in to this further with an example, 

gp1

As per above figure we have two policies inherited to “Users” OU. Policy 01 is Domain linked group policy. Policy 02 is OU linked group policy. Each of the group policy have its own values defined for the three selected settings. Based on the default group policy inheritance, Users OU will have both policies applied. According to LSDOU, Policy 02 will have lowest precedence valve as it is the closest policy for the Users OU. For Password Policy Settings, only Policy 01 has a valve defined. There for even it’s the least preferred group policy, that valve will apply to Users OU. For Windows Firewall Settings, only Policy 02 has a valve. It will also apply to the Users OU. When it comes to the Internet Explorer Settings both policies have values. That makes a conflict. The winning valve of conflicting policy settings will be decided based on LSDOU. There for the wining valve will be from Policy 02. 

Microsoft allows to change this default policy winning procedure by enforcing policies. When group policy been enforced, it will have the lowest precedence valve regardless where it’s been linked. Another advantage of the enforced policy is, it will apply even OU is blocked inheritance. If domain linked policy been enforced, it will apply to any OU under the domain and it will hold the lowest precedence. If multiple policies been enforced, all of them will take the lowest precedence numbers in order. 

To enforced a policy, load GPMC, right click on the selected group policy and then select “Enforced” option. It will enforce the policy and, change the policy icon with small padlock mark. It allows to identify enforced policies quickly from policy list. 

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In above example, Policy 01 been enforced. It is domain linked group policy. In normal circumstances Policy 02 will gets a lowest precedence value when its applies to the Users OU. But when policy been enforced Policy 01 will have the lowest precedence valve. When we look in to winning policy values of the Users OU, For Password Policy Settings it will process the Policy 01 value as it is the only one have value for it. For Windows Firewall Settings, Policy 01 do not have any value defined. So even its been enforced the winning policy setting will be from Policy 02 as it’s the only one have a valve defined. Policy 01 and Policy 02 both have values for Internet Explorer Settings. But enforced Policy 01 is in top of the policy list and winning policy setting will be from it. 

So far, we talked about conflicting policy settings from different level on domain structure. How it will work if it’s in same level? Policies in same level also apply according to precedence order. When policies are in same level the LSDOU process is no use. The winning policy will decide based on its position in the policy list. The order of the list decided based on “Linked Group Policy Objects” list. This list can view using the Linked Group Policy Objects tab in the OU detail window in GPMC. 

gp3

The order of policy in same level can be change using two methods. One method is to enforced the policy. When policy is enforced, it will take the priority from the other policies in the same level. but it will not change the “Link Order” of the policy. The order of the list can change using the up and down buttons in the Linked Group Policy Objects Tab. Link order will match the precedence order of the group policies. 

gp4

This marks the end of this blog post. Hope this was useful. If you have any questions feel free to contact me on rebeladm@live.com also follow me on twitter @rebeladm to get updates about new blog posts.

Troubleshooting Active Directory Replication Issues (PowerShell Guide)

Last Updated on January 18, 2018 by Dishan M. Francis

There are certain windows cmdlets and utilities which we can use for replication issues troubleshooting purpose. Among those, Repadmin.exe is most commonly used Microsoft utility. This is available in servers which have AD DS or AD LDS role installed. It is also part of Remote Server Administration Tools (RSAT). This utility recommended to run as Domain Administrator or Enterprise Administrator. However, it is also possible to delegate permission only to review and manage replication. 

Let’s see it’s in action 

repadmin /replsummary /bydest

above command summarizes the replication status for all domain controllers based on the replication destination. This parameter does not display the source domain controller.

repadmin /replsummary /bysrc

above command summarizes the replication status for all domain controllers based on the replication source. This parameter does not display the destination domain controller.

repadmin /showrepl REBEL-SRV01.therebeladmin.com 

above command shows the replication partners for REBEL-SRV01.therebeladmin.com and the status of last sync attempt. 

repadmin /showrepl /errorsonly 

above command will list down the replication partners which have replication errors (last sync attempt failed) 

we also can view results in CSV format.

repadmin /showrepl /csv

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repadmin /syncall REBEL-SRV01 dc=therebeladmin,dc=com

above command initiates domain directory partition synchronization with all replication partners of REBEL-SRV01. 

It will also indicate if there were any issues by doing it.

tr2

repadmin /queue

above command shows if there are any unprocessed inbound replications requests. If system keep que requests it can be due to high number of AD changes, System resource issue or too many replication partners. 

repadmin /showchanges REBELNET-PDC01 d3f89917-5fff-40a8-scc2-b148b60d9309 dc=therebeladmin,dc=com

above command list down the changes which are not replicated between server REBELNET-PDC01 and REBEL-SRV01. In here REBEL-SRV01 is the source server and it is listed with object GUID. 

tr3

repadmin /replicate REBEL-SRV01 REBELNET-PDC01 dc=therebeladmin,dc=com

above command initiate immediate directory partition replication from REBELNET-PDC01 to REBEL-SRV01.

Apart from the repadmin, there are certain PowerShell cmdlets which we can use to troubleshoot replication issues. Get-ADReplicationFailure cmdlet is one of those which can collect data about replication failures. 

Get-ADReplicationFailure -Target REBEL-SRV01

Above command will collect information about replication failures associated with REBEL-SRV01. 

This also can do with multiple servers. 

Get-ADReplicationFailure -Target REBEL-SRV01,REBELNET-PDC01

Further we can target all the domain controllers in the domain.

Get-ADReplicationFailure -Target "therebeladmin.com" -Scope Domain

Or even entire forest

Get-ADReplicationFailure -Target " therebeladmin.com" -Scope Forest

Get-ADReplicationConnection cmdlet can list down replication partner details for the given domain controller. 

Get-ADReplicationConnection -Filter *

Above command will list down all replication connection for the domain controller you logged in. 

tr4

We also can filter the replication connections based on the attributes. 

Get-ADReplicationConnection -Filter {ReplicateToDirectoryServer -eq "REBEL-SRV01"}

Above command will list down the replication connections with destination server as REBEL-SRV01.

We also can force sync object between domain controllers. 

Sync-ADObject -object “adam” -source REBEL-SRV01 -destination REBELNET-PDC01

Above command will sync user object adam from REBEL-SRV01 to REBELNET-PDC01

This marks the end of this blog post. Hope this was useful. If you have any questions feel free to contact me on rebeladm@live.com also follow me on twitter @rebeladm to get updates about new blog posts.

How to Seize FSMO Roles? (PowerShell Guide)

Last Updated on January 17, 2018 by Dishan M. Francis

In AD environment, FSMO role seize process only should use in a disaster where you cannot recover the FSMO role holder. It should be using for day to day operations. Some of the FSMO roles (RID, Domain Naming Master, Schema Master) can still afford few hours’ downtime with minimum business impacts. There for do not use the Seize option as the first option if still FSMO role holder can recover or fix. 

Once seize process is completed, the old FSMO role holder should not bring online again. It is recommended to format and remove it from network. In any given time, it is not possible to have same FSMO role appear in two servers in same domain.

In following example, there are two domain controllers in the infrastructure. REBEL-SDC02 is the FSMO role holder and REBEL-PDC-01 is additional domain controller. Due to hardware failure, I cannot bring REBEL-SDC02 online and I need to seize the FSMO roles. 

s1

In order to seize the roles following command can use,

Move-ADDirectoryServerOperationMasterRole -Identity REBEL-PDC-01 -OperationMasterRole SchemaMaster, DomainNamingMaster, PDCEmulator, RIDMaster, InfrastructureMaster -Force

s2

This command will take few minutes to complete as in background it will try to connect to original FSMO role holder. 

The only change in the command from FSMO role transfer is the -Force at the end. Otherwise its exact same command. You also can seize individual role by using Move-ADDirectoryServerOperationMasterRole -Identity REBEL-PDC-01 -OperationMasterRole <FSMO Role> -Force

In their <FSMO Role> can be replaced by the actual FSMO role value.

Once command completed we can test the new FSMO role holder. 

s3

As we can see REBEL-PDC-01 become the new FSMO role holder. 

This marks the end of this blog post. Hope this was useful. If you have any questions feel free to contact me on rebeladm@live.com also follow me on twitter @rebeladm to get updates about new blog posts.

How to Enable Active Directory Recycle Bin? (PowerShell Guide)

Last Updated on January 16, 2018 by Dishan M. Francis

Most common active directory related disasters are due to accidently deleted objects. Once object is deleted from active directory, it is not permanently deleteing from the active directory same time. As soon as an object deleted, it will set the isDeleted object value to True and move the object under CN=Deleted Object.

re1

Then the it is stay there till system reaches the tombstone lifetime value. By default, it is 180 days and this can be change if required. As soon as object passes the tombstone lifetime, it is available for permanent deletion. When I explain about the active directory database in previous section I mentioned about “online defragmentation”. It is uses garbage collector service to remove the deleted objects from the active directory database and release that space to database. This service runs in every 12 hours’ time. Once deleted object exceeded the tombstone lifetime value, it will be permanently removed in next garbage collector service cycle. the problem with this one is, during the tombstone process most of the object values are striped off. So even you were able to recover, these objects values will need to re-enter. 

With windows server 2008 R2, Microsoft introduced Active Directory Recycle Bin feature. When this feature is enabled, once object is deleted, it’s still set isDeleted object value to True and move the object under CN=Deleted Object. but instead of tombstone lifetime, now its control by Deleted Object Lifetime (DOL). Object attributes will remain same in this stage and it is recoverable easily. By default, the DOL value is equal to tombstone lifetime. This value can change by modifying msDS-deletedObjectLifetime object value. Once its exceeded the DOL, it is moved in to Recycled state and isRecycled object value set to True. By this state, it will not be able to recovered and it will be in that state till tombstone lifetime value exceed. After it reach the value it will be permanently delete from the AD. 

Active Directory Recycle Bin feature required minimum of windows server 2008 R2 domain and forest functional level. Once this feature is enabled it cannot be disabled. 

This feature can be enable using,

Enable-ADOptionalFeature 'Recycle Bin Feature' -Scope ForestOrConfigurationSet -Target rebeladmin.com

In above -Target can be change with your domain name. 

re2

Once it is enabled, we can revive the objects which is deleted using,

Get-ADObject -filter 'isdeleted -eq $true' -includeDeletedObjects

It will search for the objects where isdeleted attributes set to true. 

Now we know the deleted object and it can be restore using, 

Get-ADObject -Filter 'samaccountname -eq "dfrancis"' -IncludeDeletedObjects | Restore-ADObject

The above will restore user object dfrancis. 

re3

This marks the end of this blog post. Hope this was useful. If you have any questions feel free to contact me on rebeladm@live.com also follow me on twitter @rebeladm to get updates about new blog posts.