DHCP Troubleshooting

DHCP (Dynamic Host Configuration Protocol) automatically assigns network settings to devices when they connect to a network.

These settings include:

IP Address

Subnet Mask

Default Gateway

DNS Servers

Without DHCP, devices would need to be configured manually before they could communicate on a network.

Frequent network disconnects

Devices failing to obtain an IP address

Connected without internet access

New devices unable to join

IP addresses changing unexpectedly

Some devices working while others cannot connect

Multiple DHCP Servers:

If more than one device on the network is assigning IP addresses, devices may receive conflicting network information.

Example:

Internet -> ISP Gateway -> Router -> Devices

If both the gateway and router have DHCP enabled, connectivity problems may occur.

DHCP Pool Exhaustion:

The DHCP server has a limited pool of addresses available for assignment. If all available addresses are in use, new devices may be unable to connect.

Lease Renewal Issues:

Devices periodically renew their DHCP leases. If the renewal process fails, connectivity interruptions may occur.

Windows:

ipconfig /all

Displays:

IP Address

Default Gateway

DHCP Enabled Status

DHCP Server

Windows / macOS / Linux:

arp -a

Displays the ARP table and can help identify potential duplicate IP address issues.

Verify Only One DHCP Server Exists:

If you have both an ISP gateway and a separate router, ensure only one device is handling DHCP assignments.

Check DHCP Scope Availability:

Verify that the DHCP address pool has enough available IP addresses for all devices on the network.

Renew the DHCP Lease:

Windows:

ipconfig /release

ipconfig /renew

Review Lease Time Settings:

Verify that DHCP lease durations are appropriate for your environment and that devices are successfully renewing their leases.

Reboot Network Equipment:

Restart the modem/gateway first, then restart the router and affected devices.