DHCP Server settings
DHCP Servers are common on internal and wireless networks. If the DHCP server is not configured properly it can cause problems. Things to check in this area include:
• Is the DHCP server entry set to Relay? If so, verify there is another DHCP server to which requests can be relayed. Otherwise, it should be set to Server.
• Is the DHCP server enabled?
• Does this DHCP server use a valid range of IP addresses? Are those addresses in use by other devices? If one or more devices are using IP addresses in this range, you can use the IP reservation feature to ensure the DHCP server does not use these addresses.
• Is there a gateway entry? Include a gateway entry to ensure clients of this server have a default route.
• Is the system DNS setting being used? The best practice is to avoid confusion by using the system DNS whenever possible. However, the option to specify up to three custom DNS servers is available, and all three entries should be used for redundancy.
| There are some situations, such as a new wireless interface, or during the initial FortiGate unit configuration, where interfaces override the system DNS entries. When this happens, it often shows up as intermittent Internet connectivity. To fix the problem, go to System > Network > DNS and ensure to enable Use FortiGuard Servers. |