DHCP Failover Windows 2012

What is the OS Flavour required for doing DHCP failover in Windows 2012. Is it Standard Edition or Data Centre Edition?

The requirements are mentioned here: http://technet.microsoft.com/en-gb/library/dn338982.aspx
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DHCP Failover Server 2012

Hi,
I have a Problem with DHCP Failover in Windows Server 2012
We configured 2 Windows Server 2012 with DHCP Role and created a Scope with loadbalancing algorithm.
The Problem is, that the two DHCP Servers Show different statistic Information. DHCP 1 has 254 addresses and 218 in use. DHCP Server 2 has 254 addressses and 187 in use.
We found situations when one DHCP Server has no available IP addresses and the other one has about 40% available addresses.
Why do the Servers have different available address spaces ? We have one scope with one class c net, 254 addresses.
Our Szenario is with this config not high available, cause of sometimes running out of IP addresses on one DHCP Server.
Thanks for help
Björn
Björn Schiemann LemonTec IT Systems KG htttp://www.lemontec.de

Hi Bjoern,
Would you please provide us your detailed load balance configurations.
In load-balance mode of operation both the servers respond to client requests. Here’s how the servers ensure the distribution of client requests between themselves:
Each DHCP server on receiving the client request calculates hash of the MAC address in the client request as per hashing algorithm specified in RFC 3074. Each server hashes any MAC address
to a value between 1 and 256. If the load distribution ratio between the 2 servers is left at the default of 50:50; and if the hash of the MAC address falls between 1 and 128 then the first server will respond to the client request else if the hash is any
value between 129 and 256, the other server responds to the client. This ensures that only one server responds for a specific client. If the load distribution ratio has been changed by the admin to a different value, the distribution of hash buckets would
be in that proportion. The admin does not need to configure the MAC addresses on any server configuration a-priori.
Quote from DHCP Failover Load Balance Mode
http://blogs.technet.com/b/teamdhcp/archive/2012/08/06/dhcp-failover-load-balancing-mode.aspx
In addition, I notice that you have a Class C network for the scope, why does each DHCP server have 254 IP address available?
Thanks.
Jeremy Wu
TechNet Community Support

Minimum/Recommended Hardware Requirements for DHCP on Windows 2012 R2

Hello,
I am in the process of building two VM's on Windows Server 2012 R2 in-order to run DHCP with Failover.
Before I build my VM Servers I would like to know if there are Recommended Hardware specs that these servers should be built with?
I've been looking around for a little while and can't seem to find anyone or anywhere that these requirements are posted.
Any help would be greatly apreciated!
Thanks,
André

Totally agree with Henrik that DHCP is a very lightweight application and does not require much hardware. In fact, it is often deployed as another role on a Domain Controller. The thinking there is that the DC is something you want to have available
all the time, just like DHCP and DNS. Why not put them on the same box.
My only difference in suggestion about hardware recommendations would be to use the 2012 recommendations instead of the 2008 recommendations, though they are pretty much the same -
http://technet.microsoft.com/en-us/library/dn303418.aspx
. : | : . : | : . tim

Question on configuring DHCP failover on 2012

Is it possible to have dhcp A replicate all scopes as hot standby to dhcp B. Then have 1 single scope on DHCP B (thats not a scope on dhcp A) be replicated to dhcp A.
So basically I have Replication going in both directions. One for all scope from A to B and 1 single scope from B to A.
Can this be done?

Hi Rondefino,
It can be achieved.
We could configure failover for every scopes separately.
Server B could be the standby server for the scopes on server A. And server A could be the standby server for the scopes on server B. They will replicate automatically.
Here is the guide for configuring failover:
Step-by-Step: Configure DHCP for Failover:
https://technet.microsoft.com/en-us/library/hh831385.aspx?f=255&MSPPError=-2147217396
Best Regards,
Leo
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DHCP Failover feature in Windows 2012

I am planning to configure DHCP on windows 2012 failover (Load balanced)mode.Just want to confirm two things:
1.How will the DCHP address be assigned to clients incase the DHCP Servers loose communication between them.
2.Regarding IP helpers that i need to put onto my network switches would it be Ips for both the server or does configuration of failover feature uses single IP (as is used in cluster config)

Hi,
Sorry for the delay. I think we need to get more people monitoring this forum :)
Your questions are answered in documentation here:
http://technet.microsoft.com/en-us/library/dn338978.aspx.
From DHCP Failover Modes:
In load balancing mode, when a DHCP server loses contact with its failover partner it will begin granting leases to all DHCP clients. If it receives a lease renewal request from a DHCP client that is assigned to its failover partner, it will temporarily
renew the same IP address lease for the duration of the MCLT. If it receives a request from a client that was not previously assigned a lease, it will grant a new lease from its free IP address pool until this is exhausted, and then it will begin using the
free IP address pool of its failover partner. If the DHCP server enters a partner down state, it will wait for the MCLT duration and then assume responsibility for 100% of the IP address pool.
From DHCP Failover Architecture:
When you deploy DHCP failover, a single DHCP relay address might not be sufficient, since DHCP clients must always be able to communicate with both the primary DHCP server and the failover partner server. If both DHCP servers are located on a different subnet
than DHCP clients, this requires at least two DHCP relay agents. For example:
ip helper-address 10.0.1.1
ip helper-address 10.0.1.2
In this example, both DHCP servers are on the same subnet (10.0.1.0/24). The primary DHCP server’s IP address is 10.0.1.1 and 10.0.1.2 is the IP address for the failover partner server. If both DHCP servers are located on the same subnet, you can also configure
the subnet broadcast address (ex: 10.0.1.255) as a single DHCP relay. The use of a subnet broadcast address as a single DHCP relay is not possible if DHCP servers are located on separate subnets.
-Greg

DHCP Failover in Windows 2008 R2 and Windows 2012 R2 Environment

Hi Everyone,
We are trying to implement DHCP failover in our environment. Our IT Infrastructure consists of 4 – windows server 2008 R2 servers and 7 – Windows Server 2012 servers; 1 Main Office with 2 – DC’s and 9 branch/remote offices with one DNS server in every remote
office. All the DNS servers have 2 scopes defined on them for VOICE and Data with different Subnets.
What would be the best method to implement failover in 2008 R2 – Windows Failover Cluster or Split scope? And how to implement DHCP Failover in Windows Server 2012 R2?
Please let me know if you need more information.
Thank you for your help!
-kN

Hi,
if you can choose between 2008 R2 and 2012 R2 than go with 2012 R2 it is easy to create a DHCP failover there. Actually that is one of the new features of Windows 2012.
With Server 2012 you setup your fist DHCP server with the scopes you want to setup. Than you install the second 2012 server with DHCP role and authorized. If you have done this you going back to your first server, where you already configured your scopes.
Now right click onto the scope you want to setup for failover and select 'Configure Failover'. You can than set it up as kind of split scope (Load balance Mode) or as real fail over setup (Hot Standby). In Load balance Mode you can configure the balance of
IP addresses between the both servers, like primary has 60% IP addresses and secondary has 40%.
With Server 2008 R2 the easiest configuration is split scope. But here it depends how many IP leases you will max have and if you can absorb if one of the server is going down. Lets say you have 50 DHCP leases max, than sure, set it up as split scope. But
if you have 200 DHCP clients, than I would go with failover cluster. At the end it depends on your environment.
Sven

Windows 2012 DHCP Failover "Lost contact with partner"

We have stood up a pair of Windows 2012 DHCP servers and configured DHCP failover (in Load Balancing mode) as per the Microsoft Technet article. The two servers are on the same subnet, and time is in sync between them. Almost immediately after
configuring scopes to failover, one node loses contact with the other, and the alternate node goes to failover mode "Recover".
We have restarted both servers and services. Both DHCP servers show as available. Clicking "Replicate Failover Scopes" completes successfully with no errors, and the only two warnings in the Event Log are about credentials for Dynamic
DNS updates and a dynamic IPv6 address (which we don't use at all.)
How come they can replicate, but have "lost contact"; and how do we get the one out of "Recover" mode?

You should see Recover state only if one of the DHCP server actually went down and came back up. In this case the server which comes back up would be in Recover state but will transition to Recover_Wait state and come back to Normal after it syncs it
leases. This should be relatively quickly. Did your servers continue to remain in the Lost Contact...\Recover state for long.
Did you see any events in the DHCP Server admin channel
Microsoft\Windows\DHCP Server\Admin.
You can also enable AuditLogs (Microsoft\Windows\DHCP
Server\AuditLogs) which logs all the server to server messages. You can enable the log by right clicking on
Microsoft\Windows\DHCP Server. View->Show Analytical and Debug Logs. This will show the
Microsoft\Windows\DHCP Server\AuditLogs in event viewer. You can then right click and enable the log and see if there are any failures
being logged there.

How to test Windows 2012 R2 DHCP Failover without shutting down the service?

How can I test the Win2012R2 DHCP Failover?
There is a command or script, that i could use to test if DHCP failover is working properly?
How to monitor the sync of the objects?
How to make sure that it will do the job, if required?
Or i have to really stop DHCP server main server and see the failover?

Hello,
you have to keep in mind that this has ONLY effect for machines that request during the downtime a lease. So if your lease time is for example 8 hours a computer will ask after 4 hours for the renewal of the lease.
Means there is no problem for running machines during the test. You just need a computer to start after the service is shutdown on the first DHCP server, should take only some minutes to check if the fail over works. Then you could already start the service
again if you see the lease on the new server.
Best regards
Meinolf Weber
MVP, MCP, MCTS
Microsoft MVP - Directory Services
My Blog: http://blogs.msmvps.com/MWeber
Disclaimer: This posting is provided AS IS with no warranties or guarantees and confers no rights.
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Windows 2012 Failover Cluster - File server role (vCO)

Hi,
I wonder if anybody can shed some light on a query i have.
A windows 2012 failover cluster will be built in AD domain example.uk. Cluster File server roles will be created and will reside in this domain also.
We also have a requirement to run a cluster file server role in the child domain off secure.example.uk. Is this possible? or do the file server roles and related vCO's have to reside in the same domain as the cluster (CNO).
I know the CNO can be used to create the VCO but could a prestage a VCO in the child domain of secure.example.uk.
Mark

Hi Mark,
By default CNO will create
VCO automatically in default domain computer OU, we generally use the
KISS principle to place the CNO and VCO to the same OU, and as far as I know there no known design document indicate the VCO can be placed in different domain, therefore I suggest you place the CNO and V CO at same OU.
More information:
When Creating a New Resource or Role in Windows Server 2012 R2 Failover Cluster, the Network Name Fails to Come Online or Failed to Create Associated Computer Object in Domain
http://blogs.technet.com/b/askpfeplat/archive/2014/11/17/when-creating-a-new-resource-or-role-in-windows-server-2012-r2-failover-cluster-the-network-name-fails-to-come-online-or-failed-to-create-associated-computer-object-in-domain.aspx
CNO Blog Series: Increasing Awareness around the Cluster Name Object (CNO)
http://blogs.technet.com/b/askcore/archive/2012/09/25/cno-blog-series-increasing-awareness-around-the-cluster-name-object-cno.aspx
How to Create a Cluster in a Restrictive Active Directory Environment
http://blogs.msdn.com/b/clustering/archive/2012/03/30/10289577.aspx
Prestage Cluster Computer Objects in Active Directory Domain Services
https://technet.microsoft.com/en-us/library/dn466519.aspx
I’m glad to be of help to you!
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FTP in Windows 2012 Failover Cluster

Hi,
Understand that Windows 2012 is having much improved Failover Clustering features,however i have faced issues when i configured FTP in Windows 2012 Failover Cluster.
1) As per the process configured the shared disk for FTP data path.
2)Installaed FTP feature in both Nodes of Clustert
3)Finally created the Generic Service in Cluster Roles for FTP Service.
After the configuration i found everything working fine but when i try to failover the FTP role found that FTP resource is not moving smoothly. Also i observed that Microsoft FTP service gets in to "starting" mode in the destination Node. To run the FTP
resource Microsft FTP service should be in Started mode.
This happens only when we try to failover else it works fine if you start freshly.
Have any one tried this? Any clue about such issue ?
Regards:Mahesh

Hi,
In earlier versions of Internet Information Services, Microsoft provided generic resource monitor components to support high availability Web server instances by using the Microsoft Clustering infrastructure. However, custom code was needed to fully realize
the potential of this solution. Also, the generic scripts that Microsoft provided did not satisfy customer needs.
From IIS 7 to configure IIS in a clustered environment by using Windows Server failover clustering, you have to use a custom (scripting) code to enable such a high availability scenario.
Note:
We recommend that administrators carefully evaluate the use of Network Load Balancing (NLB) instead of using failover clustering as the primary and preferred method for improving the scalability and availability of Web applications that have multiple servers
that are running new IIS (from IIS 7) . One benefit of NLB is that all servers can actively participate in the concurrent handling of incoming HTTP requests. Another benefit is that in an NLB IIS environment, it can be much easier to support rolling updates
and rollbacks while still providing high availability of Web applications.
To configure high availability for IIS FTP servers using Failover Clustering:
Install the Web Server role on all cluster nodes.
Install the Failover Clustering feature on all cluster nodes and create the cluster.
Set up a file share that will be used for IIS shared configuration
Configure the IIS shared configuration on all cluster nodes
Configure Offline Files for IIS Shared Configuration on all cluster nodes
Configure the FTP site and specify the location of its content on one cluster node
Configure high availability for your FTP site by creating a generic script in Failover Cluster Manager
For more detailed configuration procedure please refer to following MS articles:
Note: I didn’t find IIS 8 in Windows Server 2012 failover cluster configuration guide, below guide was published for II 7 in Windows server 2008 and Windows Server 2008 R2, but its basis configuration procedures should also apply to Windows Server 2012.
How to configure FTP 7.5 for IIS 7.0 in a Windows Server 2008 failover cluster
http://support.microsoft.com/kb/974603
Configure IIS Network Load Balancing
http://www.iis.net/learn/web-hosting/configuring-servers-in-the-windows-web-platform/network-load-balancing
Deploying IIS on a Failover Cluster
http://blogs.msdn.com/b/clustering/archive/2009/06/01/9674799.aspx
Hope this helps!
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Create failover cluster to host Windows 2012 DC, Exchange 2013 and SQL as VMs

One of our clients has running Windows Essential 2012, SQL and exchange 2007 as VM on VMware for 4 years without major issue. However, the physical server is getting old and have some hardware issues recently. They have budgets to buy two Dell servers, EqualLogic
SAN, Windows server 2012 Datacenter and Exchange 2013. Is it possible for them to create failover cluster to host Windows 2012 DC, Exchange 2013 and SQL as VMs?
Bob Lin, MCSE & CNE Networking, Internet, Routing, VPN Troubleshooting on
http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on
http://www.howtonetworking.com

We will move all VMs from VMware to Hyper-V. Thank you.
Bob Lin, MCSE & CNE Networking, Internet, Routing, VPN Troubleshooting on <a href="http://www.chicagotech.net">http://www.ChicagoTech.net </a>
How to Setup Windows, Network, VPN & Remote Access on <a href="http://www.howtonetworking.com">http://www.howtonetworking.com </a>

DHCP failover from 2003 to 2012?

I know 2012 has some new DHCP failover features built in but our DC's are still 2003. :(
I'm looking for suggestions / options on how to handle this scenario. Upgrading all of the DC's isn't an option at the moment.

Hi,
The question is a little broad. How many 2012 servers are you planning to introduce and are all your DCs also DHCP servers? Are you upgrading in place or migrating to new hardware? If some DHCP servers are not also DCs I would focus on these first.
See this topic for some suggestions about how to migrate the configuration once you are ready:
Migrate to DHCP Failover.
If all your DHCP servers are also DCs I suggest adding a 2012 server to the environment and making it only a DHCP server, then add this DHCP server to your existing domain. Keep in mind that adding a 2012 server or 2012 R2 server to a 2003 domain will automatically
update the schema. I don't know if this will have any consequences for your environment - probably not - but I wanted to make you aware that this will happen.
-Greg

Windows 2012 Server multinode failover cluster (6 nodes)

Dear All,
We are facing problem of Huge time takes for cluster validation test on IBM Blade Server with Storage. The details are given below.
Escalated with IBM OEM, confirmed that "there is no hardware issue with Server and storage, Please take support from OS (Microsoft) OEM as 2 node validation test is working fine".
Server : IBM BladeCenter S-HS23
OS : Windows 2012 X64 Datacenter Edition
MPIO.SYS Version: Default came from OS
Note : Failover cluster validation test is successful on 2 nodes in 15 min with 5 shared volumes between 2 nodes and also between set of 2 on other 6 nodes.
When we are running validation test on 6 nodes its taking 30 min in list and more than 45 min potential cluster disk.
Thanks in adv for support from your end....
T & R,
Kamlesh
kamlesh

Hello,
I'd ask in the
High Availability (Clustering) subforum of the Windows Server forums.
Karl
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Server 2012 R2 DHCP Failover - Hot Standby clients not renewing with standby server

In my test network I have a pair of Server 2012 R2 DHCP servers setup for Hot Standby and they will successfully service a client request for a new request.
What I am seeing is that when I test failover the clients will not renew with the Standby server. I have to release first and then renew.
When both DHCP servers are up the state is normal and replication of configuration from the Active to Standby is working. As far as I can tell it is configured correctly.
MaxClientLeadTime is 10 minutes.
StateSwitchInterval is 10 minutes.
AutoStateTransition is set to True.
Adding that manual renews fail with a message stating that it was unable to contact the dhcp server. However if I wait for the lease to expire/auto-renew the dhcp server does indeed change to the standby. Once the primary server comes back up and the state
returns to normal I am able to manually renew.
thanks in advance

Hi,
For test, we let the active DHCP down and the standby DHCP server will take place. But when we renew an IP, client send unicast to the former DHCP
server. That’s why the first request failed.
At 7/8 of the scope lease time, the client moves into a REBINDING state and broadcasts a lease renewal request.
For more information please refer to:
DHCP Failover Examples
http://technet.microsoft.com/en-us/library/dn338973.aspx
Hope this helps.

DHCP WINDOWS 2012 FROM WINDOWS 2003

Hello
I have to migrate DHCP from Windows 2003 Standard Edition to Windows 2012 Standard Edition and i have
one red cross in " Leases" . I try two methods : by GUI and CMD ( Backup/Restore and Import/Export cmd) but
i have not solved. Any help ?
Thanks and Regards
MCITP

Hi,
Could you have a more detailed explaination or upload us a screenshot regarding the red cross in "leases"?
In addition, please check the below thread to see if helps:
DHCP Leases with a Red Cross and Event Log Errors
http://social.technet.microsoft.com/Forums/windowsserver/en-US/aaaaddbe-a8f2-41e9-87ab-be76a46b1df3/dhcp-leases-with-a-red-cross-and-event-log-errors
Best regards
Michael
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DHCP Failover Windows 2012

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