In modern network architectures, it's very important to ensure that every device has a unique IP address and with more and more devices connected to any given network managing unique IPs is important. Dynamic Host Configuration Protocol (DHCP) helps with this by using a server to assign IP addresses to devices when they join a network. The assigned IP Addresses can be leased to a device for a limited time or permanently [1]. However, if the DHCP server fails, new hosts on the network won't be assigned IP addresses, preventing them from accessing critical services like DNS [2]. Because of this, it's very important that DHCP servers have redundancy to ensure continued service even if a single server fails. In this project we will use ns3 to compare 2 different methods for DHCP failover, rating them based on the success rate during the failure (how many devices joined vs how many devices were assigned IPs) and duration of the failure (how long after the first server goes down does it take for the second server to take over) . [3] links a pair of DHCP servers as a primary and secondary server allowing the secondary to take over if the primary fails. This method is commonly used in industry as outlined by [4]. [5] expands this idea creating a hierarchy of servers that can be distributed over multiple vpn connected networks to ensure reliable DHCP over the entire set. We’ll evaluate the hierarchy of servers for multiple server counts to see how the server count impacts the reliability.
[1] R. Droms, “Dynamic Host Configuration Protocol,” Dynamic Host Configuration Protocol, Mar. 1997, doi: https://doi.org/10.17487/rfc2131.
[2] D. Garn, “The role of DHCP reviews for business continuity,” Search Networking, 2026. https://www.techtarget.com/searchnetworking/tip/The-role-of-DHCP-reviews-for-business-continuity (accessed Feb. 08, 2026).
[3] R. Fan, R. Droms, N. Griffeth, and N. Lynch, “The DHCP Failover Protocol: A Formal Perspective.” Accessed: Feb. 08, 2026. [Online]. Available: https://groups.csail.mit.edu/tds/papers/Fan/forte07.pdf
[4] dknappettmsft, “DHCP failover in Windows Server,” Microsoft.com, Mar. 27, 2025. https://learn.microsoft.com/en-us/windows-server/networking/technologies/dhcp/dhcp-failover#dhcp-failover-and-windows-failover-clustering (accessed Feb. 08, 2026).
[5] L. Trombeta and N. Torrisi, “DHCP Hierarchical Failover (DHCP-HF) Servers over a VPN Interconnected Campus,” Big Data and Cognitive Computing, vol. 3, no. 1, p. 18, Mar. 2019, doi: https://doi.org/10.3390/bdcc3010018.