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Essential DHCP Server Configuration Guide

Apr 3, 2025

DHCP Server Configuration and Management

Overview of DHCP Server Settings

  • IP Address Range: Determine specific IP addresses to be assigned by the DHCP server and their subnet mask.
  • Lease Duration: Define how long a workstation can keep an IP address.
  • DNS, Gateway, and Other Settings: Configure DNS server IP, default gateway, and other options like VoIP servers.

DHCP Address Assignment

  • Address Pools: DHCP server assigns IP from a configured pool.
  • Subnet Example: Pool 192.168.1.0/20 allows assignment within that range.
  • DHCP Reservations: Exclude or reserve specific addresses in the pool.

Configuration on Different Devices

  • Windows Server:
    • Address pools define assignable IPs.
    • Address leases show previously assigned IPs.
    • IP reservations ensure specific devices always receive the same IP.
    • Scope options for additional parameters (e.g., VoIP gateway IP).
  • Embedded Routers:
    • Start and end address define the assignable range (e.g., 10.10.10.2 to 10.10.10.100).
    • Address lease time in seconds, e.g., 86,400 seconds for 24 hours.
    • Gateway and DNS configurations for local devices.

Dynamic vs Static IP Assignments

  • Dynamic Assignment: IPs are assigned from a large pool and can change after the lease period.
  • Automatic Assignment: Remembers previous IPs for short absences.
  • DHCP Reservations: Permanent IP assignments based on MAC addresses (also called static DHCP assignment).

Lease Time and Renewal

  • Lease Timer: Duration a device holds an IP before renewal or reallocation.
  • T1 Timer: Checks in at 50% of lease time; renews lease if server is available.
  • T2 Timer: Checks in at 87.5% if T1 fails, tries to rebind with any DHCP server.

Visualizing the DHCP Process

  • Example with an 8-day lease:
    • T1 Timer: Check-in at 4 days.
    • T2 Timer: Rebinding starts at 7 days if no response from the original server.
  • Redundancy: If primary DHCP server fails, a redundant server can renew the IP.

These notes outline the key elements of configuring and managing a DHCP server, including address allocation, lease management, and redundancy measures.

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