Dynamic Host Configuration Protocol and IP Address Assignment CIS 238 Oakton Community College

Methods for Assigning IP Addresses Static assignment – Manually assign an IP address to a host Dynamic assignment – Configure a host to obtain an IP address automatically using DHCP (Dynamic Host Configuration Protocol)

DHCP Lease Process

DHCP Operation Common problem on networks attempting to implement DHCP: routers do not pass broadcasts Solutions – Configure a router to pass DHCP traffic (smart relay) – Place second DHCP server on same segment as the client – Use a DHCP relay agent to act as a proxy for a DHCP server

DHCP Definition Create DHCP Scope Define dynamic pool Define lease reservation(s) Define gateway Define scope options – DNS, Active Directory

DHCP Scope Options Name and Description IP Address range Subnet mask Add Exclusions Lease duration Configure DHCP Options Local specific options (Windows, VoIP) - Options that apply to all clients in one scope only -Vendor-defined option classes - User-defined option classes - Reserved client options

Integrating DHCP and DNS You can configure DHCP to create Dynamic DNS entries for clients that do not support DDNS – Helps with support of legacy, non-DDNS aware clients Windows clients can register their own A records but they still rely on the DHCP server to create reverse lookup records

Troubleshooting DHCP A scope that has run out of addresses – Decrease length of lease for the scope – Increase range of addresses in the scope – Renumber entire scope with new, larger range of addresses – Remove some clients from overcrowded network segment An improperly configured network – Place a DHCP server on each subnet – Implement DHCP relay agents on subnets without DHCP servers DHCP Service down or missing Relay Agent ipconfig /all or ifconfig –a Windows: xx.xx addresses on an interface or showing up on a network segment (no local DHCP server or relay).