The protocol maintains a pool of available IP addresses and dynamically assigns them to devices as they connect to the network. This dynamic allocation is particularly beneficial in environments where devices frequently join and leave the network, such as in corporate offices, schools, and public Wi-Fi hotspots.

Additionally, DHCP supports the concept of lease time, which specifies how long a client can use an assigned IP address before it must request a renewal. This mechanism optimises IP address utilisation, ensuring that unused addresses are returned to the pool and made available for new clients.

DHCP Lease and Lease Renewal Process

When a DHCP server assigns an IP address to a client, it does so for a limited time known as the lease period. The lease period defines how long the client is allowed to use the assigned IP address before it must renew the lease.

Lease Expiration: As the lease period approaches expiration, the client attempts to renew its lease by sending a DHCP Request message directly to the server that issued the original lease. If the server acknowledges the request, the client retains its IP address and continues to operate normally.
Lease Renewal Failure: If the DHCP server does not respond to the renewal request (e.g., due to network issues or server downtime), the client may attempt to request a new lease. If the lease expires without renewal, the IP address is returned to the pool of available addresses, allowing other devices to use it.

DHCP Security Issues

Despite its advantages, DHCP is vulnerable to various security threats that can compromise network integrity. One of the primary concerns is DHCP spoofing, where an unauthorised DHCP server responds to client requests with malicious configuration information. This can lead to:

Man-in-the-Middle Attacks: Attackers can redirect clients to malicious servers, intercepting data or redirecting traffic to malicious sites.
IP Address Conflicts: Spoofed DHCP servers can allocate the same IP address to multiple devices, resulting in network instability and connection issues.

To mitigate these risks, network administrators can implement several security measures, including:

DHCP Snooping: This feature allows switches to filter DHCP messages and ensure that only authorised DHCP servers can respond to clients.
Port Security: Limiting the number of devices that can connect to a switch port helps prevent unauthorised access.
VLAN Segmentation: Isolating DHCP servers and clients within different VLANs can help limit the impact of potential spoofing attacks.

Differences Between DHCPv4 and DHCPv6

DHCP has evolved to support the IPv6 addressing scheme, leading to the development of DHCPv6. While both versions serve similar functions in IP address allocation, there are notable differences between them:

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Feature	DHCPv4	DHCPv6
Address Space	Supports IPv4 addresses	Supports IPv6 addresses
Configuration Parameters	Can provide additional parameters	Typically provides fewer parameters
Stateless Vs Stateful	Primarily stateful