DHCP High Availability:-
A highly available solution must account for all possible points of failure, including server failures, WAN link interruptions, and router failures. You can increase the fault tolerance and availability of your design by using one or more of the following, depending on your needs and hardware cost considerations:
You can increase fault tolerance by splitting DHCP scopes between multiple DHCP servers. With a split-scope configuration, if one server becomes unavailable, the other server can take its place and continue to lease new IP addresses or renew existing clients.
Splitting DHCP scopes also helps to balance server loads.
When splitting the IP address pool of a scope between two servers, assign the same scope to both servers, and exclude opposite portions of the address range. You also need to make identical reservations at both DHCP servers, so that either server can assign the reserved IP address, ensuring that the intended device receives the address that is reserved for its use.
Clustered DHCP Servers:-
Windows Clustering can automatically detect the failure of an application or server and restart the application on or transfer the server role to an alternate server. Users experience only a brief break in service.
Windows Clustering creates a virtual DHCP server so that if one of the clustered nodes fails, the namespace and all of the services contained in that node are automatically transferred to a second node. No changes are visible to the client, which sees the same IP address for the clustered DHCP servers.
Standby Servers:-
A standby server and its scopes are not activated for use under normal conditions, and are activated by the administrator only when needed, such as when a DHCP server fails or is taken offline for an extended period of time. Standby servers require manual administration to ensure failover transition, and therefore might not be as effective as other failover methods, such as split scopes and clustered servers.
To use a standby configuration, configure an additional DHCP server to server as a backup if the primary server goes offline. You can either configure the standby server to be identical to your primary DHCP server or configure the standby server with unused scopes to temporarily replace the primary DHCP server.
A highly available solution must account for all possible points of failure, including server failures, WAN link interruptions, and router failures. You can increase the fault tolerance and availability of your design by using one or more of the following, depending on your needs and hardware cost considerations:
- Split-scope configurations
- Clustered DHCP servers
- Using standby servers
Split-Scope Configurations:-
Splitting DHCP scopes also helps to balance server loads.
When splitting the IP address pool of a scope between two servers, assign the same scope to both servers, and exclude opposite portions of the address range. You also need to make identical reservations at both DHCP servers, so that either server can assign the reserved IP address, ensuring that the intended device receives the address that is reserved for its use.
Clustered DHCP Servers:-
Windows Clustering can automatically detect the failure of an application or server and restart the application on or transfer the server role to an alternate server. Users experience only a brief break in service.
Windows Clustering creates a virtual DHCP server so that if one of the clustered nodes fails, the namespace and all of the services contained in that node are automatically transferred to a second node. No changes are visible to the client, which sees the same IP address for the clustered DHCP servers.
Standby Servers:-
A standby server and its scopes are not activated for use under normal conditions, and are activated by the administrator only when needed, such as when a DHCP server fails or is taken offline for an extended period of time. Standby servers require manual administration to ensure failover transition, and therefore might not be as effective as other failover methods, such as split scopes and clustered servers.
To use a standby configuration, configure an additional DHCP server to server as a backup if the primary server goes offline. You can either configure the standby server to be identical to your primary DHCP server or configure the standby server with unused scopes to temporarily replace the primary DHCP server.
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