We have moved our DHCP from Windows server to Firewall device around 6 years ago when we had some issues with Windows server. Windows PCs and Windows server (2012) as AD/DC/File server. You can monitor DHCP relay activity by looking at the output from the show dhcprelay statistics EXEC command. DHCP and DNS on Firewall Posted by SPR1 on Mar 15th, 2021 at 3:16 PM Needs answer Firewalls DHCP & IPAM Windows Server We are SMB with around 40+ users. You can use the following commands to accomplish this:įirewall(config)# dhcprelay server 192.168.1.1 dmz Firewall(config)# dhcprelay timeout 120 Firewall(config)# dhcprelay setroute inside Firewall(config)# dhcprelay enable inside The firewall's inside interface address is given to the clients as a default gateway. Server: Specify the IP address of DHCP server. The firewall waits 120 seconds for a reply from the DHCP server. To specify the DHCP server, navigate to DHCP Server and click Add. ![]() DHCP Relay ExampleĪ DHCP relay is configured to accept DHCP requests from clients on the inside interface and relay them to the DHCP server at 192.168.1.1 on the DMZ interface. This is the interface where DHCP clients are located. The DHCP relay service is started only on the firewall interface named client_ifc (inside, for example). This causes the DHCP reply packet to list the firewall interface closest to the client, the interface named client_ifc, as the default gateway.įirewall(config)# dhcprelay enable client ifc You can configure the firewall to replace any default gateway information with its own interface address. By default, this information is passed on through the firewall so that the client receives it. When DHCP replies are returned by a real DHCP server, a default gateway could be specified in the reply packet. (Optional) Inject the firewall interface as the default gateway:įirewall(config)# dhcprelay setroute client ifc You can adjust the timeout to seconds (1 to 3600 seconds).ģ. If a reply is not returned within that time, nothing is relayed back to the client, and any overdue server reply is simply dropped. ![]() If a reply is returned within that time, it is relayed back toward the client. (Optional) Adjust the DHCP reply timeout:įirewall(config)# dhcprelay timeout secondsīy default, the firewall waits 60 seconds to receive a reply from a real DHCP server. If multiple servers are defined, DHCP requests are relayed to all of them simultaneously.Ģ. When DHCP requests (broadcasts) are received on one firewall interface, they are converted to UDP port 67 unicasts destined for the real DHCP servers on another interface. ![]() You can repeat this command to define up to four real DHCP servers. Define a real DHCP server:įirewall(config)# dhcprelay server dhcp server ip server ifcĪ real DHCP server can be found at IP address dhcp_server_ip on the firewall interface named server_ifc (inside, for example). Follow these steps to configure a firewall to act as a DHCP relay: 1.
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