The Dynamic Host Configuration Protocol (DHCP) is at the core of almost every enterprise network forming a mission-critical service that is the cornerstone of reliable network access. Yet, usually we see this service configured as a single point of failure with little regard to high availability or disaster recovery. While longer lease durations are often used to provide some cushion in the event of unavailability, this should not be used as the only protection against system failure.
If a client makes a DHCP request and no server is online to respond to it, then the client cannot acquire the network settings it needs and consequently the user will have no network access. The loss of connectivity can result in unreachable websites, lost productivity, dissatisfied customers and lost revenue.
Even a relatively small single site solution calls for DHCP resilience.
For redundancy, you probably need to have two DHCP servers. Most desktop OS's can cope pretty well with not getting a reply to a DHCP request, as they will continue to use the address they had, at least until the lease expires. In today’s workplace with a proliferation of devices requiring network access it is not best practice to assign addresses with long lease times as the range of available addresses can soon be depleted.
Good network design should wherever possible remove single points of failure so logically the solution is to deploy more than one DHCP server.
With two servers deployed, you can either split DHCP scopes across them, or cluster them. If you split scopes over multiple servers, you need to do ensure that servers are each configured with a different pool of addresses. You can use both methods for even greater resilience but this adds complexity to the design. For a single site solution however this is probably overkill and potentially very costly.
Our solution eliminates complexity and permits the deployment of a back-up DHCP server within the same domain as the primary. Primary and back up servers are managed by an agent that ensures that only one DHCP server is running at any one time. The servers are scheduled to synchronise their address allocation tables on a regular basis and in the event that the active server goes offline the agent will automatically start the failover server.
Improve your organisation’s DHCP resilience:
- at minimal cost
- with lowered complexity
- within short timescales
For more information speak with one of our team.
High Availability DHCP (Dynamic Host Configuration Protocol) Solution has not been reviewed by any customers.
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The views and opinions submitted and expressed here are not those of Microsoft.