Dynamic Host Configuration Protocol

The Dynamic Host Configuration Protocol is used to dynamically provide IP address configuration to clients.When a client is configured to use a dynamic IP address the following process is performed at startup:

1.The client sends an DHCPDiscover broadcast which all available DHCP servers can respond.

2.The DHCP servers then sends a DHCP offer packet containing IP address information that the client can use.

3.The client sends a DHCP Request indicating that it accept the offer, the first offer received is then used.

4.The server responds with a DHCP Ack that identifies that the DHCP server knows that the offer was that was accepted.

Because most routers block broadcast packets from passing between networks means that DHCP Discover packet are not able to cross networks ,so to allow a DHCP server to service multiple networks you need to implement a DHCP relay.

Installing DHCP Server on Windows Server 2016

1.In Server Manager click manage and then Add Roles and Features

2.In the Wizard click Next

3.Next choose Installation type and click next

4.On Select Destination server page select the server you would like to serve as DHCP server

5.On select server roles page select the DHCP server check box click Add Features and click next.

6.Read the information on DHCP server page and click next.

7.On Confirm Installation Page click Install and wait for the installation to complete and click close.

After installation the server needs to be authorized before it can begin servicing requests. This is done so that the server does not give out incorrect configuration information to the clients. Then we need to configure the DHCP server to start handing out addresses we need to create a scope.The scope defines the IP address range and options like subnet mask and default gateway.

Create Dhcp Scopes

1.In the DHCP management console expand the server and click IPv4

2.Right-click IPv4 and click New Scope

3.In the Wizard click next

4.On the Scope Name Page enter an name for the scope and click next

5.On the IP address Range page enter the Start ,End address Subnet Mask and click next.

6.On Add Exclusions and Delay page enter any IP address that should not be given to clients

7.On the Subnet delay in milliseconds you can enter a number that the scope should wait before responding.

8.On the Lease Duration page enter how long you would like you clients to use the address (When you create a scope the default is eight days.)

9.On the Configure the DHCP options page click No I will configure these options later and click next.

10.On the Completing the New Scope Wizard page click Finish

11.In DHCP management console right-click the scope and click Activate.

DHCP High Availability

When the DHCP service fails, clients no longer have IPs. Before Windows Server 2012, DHCP failover was not possible because DHCP servers were independent and unaware of each other.

The solution since Windows Server 2012 is the new DHCP failover feature, which is still supported in Windows Server 2016 and enables two DHCP servers to provide IP addresses and optional configurations to the same subnets or scopes.You now can configure two DHCP servers to replicate lease information.

If one servers fails, the other server services the clients for the entire subnet. You cannot configure DHCP failover for more than two DHCP servers. In addition, DHCP failover cannot be used with IPv6 scopes and subnets.

Configuring DHCP Failover

To configure the Windows Server 2016 DHCP failover feature, you can choose between two modes. Hot standby or load-balanced mode.In hot standby mode one DHCP server is primary for the scope and the second server is the standby node.

This configuration is useful when there is a local DHCP server in a site and another server is at a different site. In load-balanced mode both DHCP servers responds to client requests the two servers coordinate to prevent duplicate offers.This mode is best when both servers are in the same site.

To configure failover, use the Configuration Failover Wizard,launch by right-clicking the IP node or the scope node.The DHCP servers cannot be in different domains, but they can exist in different sites and subnets.

1. In the DHCP Manager, under the IPv4 node, select Configure Failover.

2. On the Configure Failover page, select the scope you want to replicate.

3. On the Specify the Partner Server to Use for Failover page, type the name of your partner server.

4. On the Create a New Failover Relationship page, leave the Relationship Name value. Here you can configure the Maximum Client Lead Time setting, the DHCP failover mode, Load Balance Percentage, State Switchover Interval, Message Authentication, and Shared Secret. Under Mode, select Hot Standby. Leave the default settings.

5. Finish the DHCP failover configuration.