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

Similar Messages

Can I failover a DHCP failover server?

Greetings,
I'm in the process of putting together an enterprise wide DHCP design. I'm planning on leveraging the hot failover feature in Server 2012. I'll be using a hub-and-spoke topology with a server in our primary datacenter acting as the failover partner
for all the DHCP servers at branch offices.
My question is can I failover the failover server? Basically can I configure the failover partner for all the primary servers to fail over to yet another DHCP server in a secondary datacenter?
Thanks!

One line answer to your question is no. Since a given scope on a DHCP server can be part of one and only one failover relationship and given that all the scopes on your Hub DHCP server are part of different failover relationships distributed across
your spoke servers you cannot make those scopes a part of failover relationship with another DHCP Server.
Having said that, in case your hub DHCP Server fails the spoke DHCP servers can take over. Yet if you are concerned about data loss then you can have appropriate disaster recovery\backup solutions in place to safeguard the DHCP data on the hub server.

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
This posting is provided AS IS with no warranties or guarantees , and confers no rights.
Ahmed MALEK
My Website Link
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Migration DHCP from server 2012 R2 to 2012

Hi,
how to do DHCP role transfer from windows server 2012 R2 server to 2012 server. tried to export and import db ,while importing db getting an error "TLS configured but not supported"
Thanks,
Shamal

Hi,
In addition, you can install Windows Server Migration Tools on the destination and source servers and then use Windows PowerShell cmdlets to perform migration. For more detailed information, please refer to the links below:
DHCP Server Migration: Preparing to Migrate
Install, Use, and Remove Windows Server Migration Tools
DHCP Server Migration: Migrating the DHCP Server Role
Best regards,
Susie

SNMP OID for DHCP on Server 2012

We recently installed Server 2012 standard on one of our servers and were trying to keep a graph of DHCP lease use. Anyway the OIDs for DHCP in Server 2008 R2 started with "1.3.6.1.4.1.311.1.3.2.1.1". If I try to snmpwalk these same OIDs on the new Server
2012 (We the DHCP server configured and active), I get:
Error in packet.
Reason: (genError) A general failure occured
Failed object: SNMPv2-SMI::enterprises.311.1.3.2.1.1
I'm using SNMPwalk and I've never had a problem with this before. Any idea what would cause this? Thanks!
Thanks!

I'm having the same issue. OIDs just don't work against a 2012 DHCP server. I can snmpwalk other OIDs, just not DHCP :(
Firewall has been disabled (and there were already adequate snmp rules allowing the traffic). Since I can query other OIDs, I'm ruling out firewall.
Has this info been removed in 2012?

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
Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact [email protected]

DHCP Failover / Migrate DHCP Server to another Machine

We have DHCP Server Installed in Domain Controller with Windows Server 2008 R2 Based OS.
I have Checked that there is no way to make the DHCP Failover in Server 2008 R2.
Can anyone help me to get some level of Failover in DHCP?
or
If I want to migrate the DHCP to Server 2012 what is the Best Practice?

Hello,
There is no big challenge for configuring DHCP failover in Windows 2008 platform. Kindly go through with this link for configuring DHCP failover. I am sure it will help you to completing your task.
1> Step-by-Step: Configure DHCP for Failover
http://technet.microsoft.com/en-us/library/hh831385.aspx
2> DHCP Step-by-Step Guide: Demonstrate DHCP Failover – Clustering in a Test Lab
http://technet.microsoft.com/en-us/library/ee405263(v=ws.10).aspx
Process of Migration DHCP Server 2008R2 to Windows 2012
• Firstly, you can disable the DHCP role in Windows Server 2008 R2. However, if the Windows Server 2012 is down, the clients cannot renew their IP lease duration and obtain IP address.
Therefore, it is recommended to leave the DHCP role in Windows Server 2008 R2 and deploy high availability. Windows Server 2012 brings the new feature: DHCP failover. However it requires both DHCP Servers are Windows Server 2012. Consider another Server
is Windows Server 2008 R2, we have to choose one of the following:
>> DHCP in a Windows failover cluster. This option places the DHCP server in a cluster with an additional server configured with the DHCP service that assumes the load if the primary DHCP server fails. The clustering deployment option uses
a single shared storage. This makes the storage a single point of failure, and requires additional investment in redundancy for storage. In addition, clustering involves relatively complex setup and maintenance.
>> Split scope DHCP. Split scope DHCP uses two independent DHCP servers that share responsibility for a scope. Typically 70% of the addresses in the scope are assigned to the primary server and the remaining 30% are assigned to the backup server.
If clients cannot reach the primary server then they can get an IP configuration from the secondary server. Split scope deployment does not provide IP address continuity and is unusable in scenarios where the scope is already running at high utilization of
address space, which is very common with Internet Protocol version 4 (IPv4).
More references:
Step-by-Step: Configure DHCP for Failover (Windows
Server 2012)
How
to configure split-scope using wizard
DHCP
Step-by-Step Guide: Demonstrate DHCP Split Scope with Delay on a Secondary Server in a Test Lab
DHCP
Step-by-Step Guide: Demonstrate DHCP Failover – Clustering in a Test Lab
If you need snap shot of migration then follow these links.
http://blogs.technet.com/b/canitpro/archive/2013/04/29/step-by-step-migration-of-dhcp-from-windows-server-2003-to-windows-server-2012.aspx
http://www.mehrban.net/migrating-dhcp-from-windows-2008-to-windows-2012
Deepak Kotian.
MCP, MCTS, MCITP Exchange 2010 Ent. Administrator
Disclaimer:
Please take a moment to "Vote as Helpful" and/or "Mark as Answer", where applicable.
This helps the community, keeps the forums tidy, and recognizes useful contributions. Thanks!
All the opinions expressed here is mine. This posting is provided "AS IS" with no
warranties or guarantees and confers no rights.

Cannot create Failover Relationship between to Server 2012 DHCP Servers

Hello all!
I am trying to create failover relationships for several scopes on a Server 2012 DHCP server. This all worked in my test environment, but the production environment keeps giving me errors saying that the scope cannot be added on the target server.
Does anyone know what Error: 20010 in this case means?
Thanks.

Hope this helps
http://blog.rolpdog.com/2012/11/dhcp-failover-breaks-with-custom-options.html
http://popravak.wordpress.com/2014/05/31/windows-server-2012-dhcp-failover-with-or-without-custom-dhcp-attributes/
Rgds
Milos
PS: List of errors
http://msdn.microsoft.com/en-us/library/windows/desktop/aa363378(v=vs.85).aspx

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.

Server 2012 DHCP Server Failover - Hot Standby

Hi There
I'm running two Windows Server 2012 R2 servers, they are configured in a Hot Standby mode for DHCP Failover. ServerA, is the local server at the site and is configured to Failover to ServerB. But I'm having an issue where after the state of ServerA changes
from Normal to Communication_Int and then back from Communication_Int to Normal that it's no longer leasing any IP address to my Windows 7 clients until you restart the DHCP service on ServerA. I've replicated this in my lab environment as well.
1. Disable Network Adapter on ServerA or disconnect Network - State changes from Normal to Communication_Int. ServerA and ServerB loses contact.
2. Enable Network Adapter on ServerA or reconnect Network - State changes from Communication_Int to Normal. ServerA and ServerB re-establishes contact.
3. Connect new computer to LAN, or release IP on client computer, and then try to obtain an IP address\renew.
4. Client computers time out trying to communicate with DHCP server, but as soon as you Restart the DHCP service on ServerA the client machines obtain an IP address.
Has anyone else experienced this? If so is there a fix/workaround for this?
Thanks

Hi
Sorry for only replying now.....
Disabled firewall on ServerA, ServerB and client machine. Issue still occurring.....

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

Server 2012 R2 DHCP authentication error (1046-DHCP)

Hello all, here is my story, hope someone can help me solve it.
Goal :
Getting the DHCP running on windows server 2012 R2
Current situation :
We have two different domains in one forest (domain-A & domain-B).
Domain-A has several w2k8r2 servers. In Domain-A we have two server 2008 R2 domain controllers (serverA1 & serverA2). On both servers the DHCP rule is installed and running.
Domain-B has several w2k8r2 servers. In Domain-B we have two server 2008 R2 domain controllers. Both servers don’t have DHCP server role !
We installed 2 w2k12R2 servers (server-b1 & server-b2) in domain-B and promoted to domain controller. We installed the DHCP server role on server-b1 & server-b2 configured the failover. The domain function lever is still w2k8r2.
The change :
In domain-A we unauthorized the DHCP server-A1 & server-A2 and deleted the DHCP server role.
Restarted server–A1 & server-A2 and checked if the DHCP server role is removed.
In domain-B we restarted server-B1 & server-B2. We authorized the DHCP on server-B1 & server-B2.
The error :
The DHCP didn’t go online, it gives the following error message in the event viewer (this is the only error message about the DHCP server)
Eventid 1046, DHCP-Server
The DHCP/BINL service on the local machine, belonging to the Windows Administrative domain Domain-B, has determined that it is not authorized to start.
It has stopped servicing clients. The following are some possible reasons for this:
This machine is part of a directory service enterprise and is not authorized in the same domain.
(See help on the DHCP Service Management Tool for additional information).
This machine cannot reach its directory service enterprise and it has encountered another DHCP service on the network belonging to
a directory service enterprise on which the local machine is not authorized.
Some unexpected network error occurred.
Tried solutions :
1) checked the local network settings, the dns server is the one in the old forest (domain-A) this is correct !
2) Checked with adsiedit.msc if there was still an entry that was looking at server-A1 & server-A2. Nothing found. 3) I unauthorized the 2 new servers (server-b1 and server-b2) I installed a new w2k12R2 server in domain-A1, installed the dhcp server role
only. Tried to authorizes the dhcp server but the exact same error.
looking forward to all the ideas, and the solution
J
Design is the Technology

Hi,
According to your description, when we installed a new windows server 2012 r2 in the domain A and only installed the DHCP role, the authorization was still not success. So please check if the unauthorized and authorized process was success. To verify if
the DHCP servers have been authorized, please try to run netsh dhcp show server
command, then we can see the DHCP server which was authorized. And you mentioned that you have checked with ADSIEdit to see if there was an entry. Yes, we can make full use of ADSIEdit. If a DHCP server was authorized successfully, there must be an
entry about the DHCP server in the ADSIEdit. So please check if there are some entries in the ADSIEdit of all your DCs in the domain. Ensure that only one entry about this new windows server 2012 r2 in the ADSIEdit.
If there are different in the several DCs, please try to use AD replication to make the data consistent.
And we must log on the server as an administrator to complete this operation.
To check the entry, please follow steps below,
1. Start adsiedit.msc.
2. Open the Configuration container.
3. Expand Services.
4. Expand Net Services.
Best Regards,
Tina

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 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 Server 2012 DHCP Event ID: 20291

Hi,
We have a DHCP failover set up with the default settings.
We have always noticed numerous Event ID: 20291 errors in the Event Log. After following the instructions installing patches KB2919355 and KB2955135, deleting the failover relationship, and recreating it, we're still getting numerous errors with different
scopes, and the error repeats repeatedly for the same IP. Sometimes users would get duplicate IP address error.
When we click on "Display Statistics" on various scopes for each partner, they show different numbers as far as how many IPs are leased by each.
Any ideas on what this could mean? We're ready to just remove the failover relationship completely and go back to split scope.
http://blogs.technet.com/b/teamdhcp/archive/2014/02/26/dhcp-failover-patch-to-address-a-reservation-issue-and-another-issue-related-to-failover-partner-not-accepting-state-transition-from-bad-address-gt-active-has-been-released.aspx?pi47623=2
http://support.microsoft.com/en-us/kb/2955135
Source: Microsoft-Windows-DHCP-Server
Date: date/time
Event ID: 20291
Task Category: DHCP Failover
Level: Error
User: NETWORK SERVICE
Computer: DHCP-NODE
Description: A BINDING-ACK message with transaction id: Transaction_Number was sent for IP address: IP_Address with reject reason: (Reject Reason Unknown) to partner server: DHCP_Partner_Server for failover relationship: DHCP_Failover_Relationship_Name.

Hi,
According to your description, my understanding is that DHCP failover with load sharing mode, Event Log displays numerous Event ID: 20291, and the error repeats repeatedly for the same IP.
As KB 2955135 mentioned that Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. If both servers are Windows Server 2012 R2, please install KB3000850(November 2014 update rollup
for Windows Server 2012 R2), download link:
http://www.microsoft.com/en-us/download/details.aspx?id=44975
Note:
Before you install this update, you have to first remove the failover relationship, install the update to both DHCP nodes and restart them, and then reestablish the failover relationship.
Best Regards,
Eve Wang
Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Support, contact [email protected]

DHCP Failover Server 2012

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