DHCP Failover Requirements
In this article i am sharing detailed pre-requisites and plans needed for DHCP Fail-over implementation.
Upcoming article detailed about how to setup DHCP fail-over in your infrastructure.
Updated: July 31, 2013
Applies To: Windows Server 2012 R2, Windows Server 2012
Requirements to deploy DHCP failover are the following:
Item
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Requirement
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Details
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Operating system
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Windows Server® 2012, or a later operating
system is required.
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Both DHCP servers in a DHCP failover
relationship must be running Windows Server® 2012 or a later operating
system. Servers do not need to both be running the same operating system, but
this is recommended to ensure consistent replication of settings.
|
Role services
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The DHCP Server role service is required.
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Both computers participating in a DHCP
failover relationship must have the DHCP Server role installed and running.
The DHCP Server service can be paused, but must not be stopped.
Additional roles, role services, and
features are optional.
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Network
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DHCP servers can be on the same network or
on different networks. The network connection between DHCP failover partners
must be uninterrupted.
Both DHCP servers must be able to
communicate with each other, and with all DHCP clients that will receive DHCP
leases from failover-enabled scopes.
Both servers must also be time synchronized
to within one minute of each other.
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DHCP servers can communicate with each other
directly, or through IP routing.
DHCP servers can communicate with DHCP
clients either directly or using DHCP relay.
For more information about configuring DHCP
relay agents for a DHCP failover deployment, see DHCP Failover Architecture.
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IP addresses
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DHCP servers should be configured with
static IP addresses.
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To ensure a persistent TCP connection
between DHCP failover partners is maintained, it is important to use a static
IP address on all DHCP server network interfaces.
If the static IP address of a DHCP server
needs to be changed, for example during DHCP migration, you must first delete
all DHCP failover relationships that exist on that server, and then recreate
the relationships when the new IP address is active.
For more information about communication
between DHCP failover partners, see DHCP Failover Communications.
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DHCP scopes
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At least one IPv4 DHCP scope must be
configured on the primary DHCP server.
The same DHCP scope ID, or an overlapping
scope, must not be configured on the failover partner.
|
Other DHCP scopes that are not overlapping
can be configured on the failover partner, but are not required. Scopes that
are not configured for DHCP failover are not affected.
The DHCP scope does not need to be active.
An inactive DHCP scope that is replicated to a DHCP failover partner server
will also be inactive on the failover partner.
You cannot configure DHCP failover using two
DHCP servers that are already configured for a split-scope DHCP deployment
because the same DHCP scope ID is present on both servers. Initial
replication of a DHCP scope to the failover partner will fail if the scope ID
already exists on the destination server.
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Domain membership
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Not required.
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DHCP servers can be workgroup computers or
domain member computers. However, workgroup computers cannot be authorized in
Active Directory. For more information, see Authorizing DHCP servers.
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Prerequisite checks
The following prerequisite checks are made before enabling DHCP
failover:
Check performed
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Error message displayed
|
||
DNS name resolution for the failover partner
server
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Unable to resolve the specified DNS name.
|
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Valid IP address specified for the failover
partner server
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The specified IP address <x.x.x.x> is
invalid.
|
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The server has a network connection to the
failover partner server
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The specified DHCP server is not reachable.
Please provide a DHCP server that is reachable.
|
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The operating system on the failover partner
server
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The version of specified DHCP server does
not support failover.
|
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The user is a member of the DHCP
Administrators group, or equivalent, on the failover partner server
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You do not have permissions to perform this
operation on the remote DHCP server.
|
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The maximum number of failover relationships
for either DHCP server
|
The local/partner server already has 31
(maximum allowed) failover relationships. A server cannot have more than 31
failover relationships.
|
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The DHCP Server service is running on the
failover partner server
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DHCP server is not running on the specified
server. Please ensure that DHCP server is running on the specified server.
|
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Time is synchronized between both servers
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The time difference between this server and
the specified partner server is greater than the permissible value of x
minutes. It is recommended to ensure that both servers are time synchronized
before configuring failover. You could setup Network Time Protocol (NTP)
service on both servers to ensure time synchronization.
|
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Are scopes already present on the failover
partner server
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Following scopes already exist on the
specified partner server. These scope(s) will need to be deleted on the
partner server before configuring failover.
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Checklist:
Deploy DHCP Failover
Updated: July 31, 2013
Applies To: Windows Server 2012 R2, Windows Server 2012
This checklist includes cross-reference links to important
concepts about deploying DHCP failover. It also contains links to procedures
you can use to configure DHCP failover.
Complete the tasks in this checklist in
order. When a reference link takes you to a conceptual topic or to a
subordinate checklist, return to this topic after you review the conceptual
topic or you complete the steps in a procedure so that you can continue with
the remaining tasks in this checklist.
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Checklist: Deploy DHCP Failover
Task
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Reference
|
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Review DHCP failover concepts and
components; identify your design goals.
|
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Review DHCP failover requirements and
specifications; decide on a deployment topology; identify pilot sites; document
deployment decisions and processes.
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Configure DHCP failover
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Replicate DHCP failover settings (optional)
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Migrate to DHCP failover (optional)
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