Cisco Router DHCP Services Implementation

Implementing DHCP Services on a Cisco Router

• Using the right tool for the right job is important, and in this scenario, having a remote router or firewall act as a DHCP server for the local network makes sense instead of sending DHCP services over a slow wide area network.

• The scenario involves a remote branch office with a router and a PC, and the goal is to configure the router to act as a DHCP server to dynamically hand out IP addresses to the PC.

  Not all routers are capable of functioning as a DHCP server. However, many modern routers designed for small business or home use do include DHCP server functionality as a standard feature. It's always best to check your router's specifications or user manual to determine if it can support DHCP server capabilities.

  Enterprise-level routers or older, basic routers may not have DHCP server functionality built-in. These types of routers may require manual configuration of DHCP services through an external server or device.

Configuring the Router

• The router is configured to be a DHCP server using the command IP DHCP pool and naming the pool (e.g., OURPOOL).
• The network command is used to specify the network address space (e.g., 10.3.0.0/24) that the router will support as a DHCP server.
• Exclusions can be set up using the IP DHCP excluded-address command to exclude certain IP addresses from being handed out (e.g., 10.3.0.1-10 and 10.3.0.50-254).

Specifying Options

• The default-router option is used to specify the default gateway that clients should use (e.g., 10.3.0.3).
• The DNS option is used to specify the DNS server that clients should use (e.g., 8.8.8.8).

Verifying Connectivity

• Before configuring the DHCP server, it's essential to verify that the router has connectivity to the internet using the ping command (e.g., ping 8.8.8.8).
• If the ping is not successful, it may be necessary to check the port address translation (PAT) configuration.

Debugging and Testing

• Debugging can be used to get additional information about the DHCP process on the router using the debug command (e.g., debug IP DHCP server packets).
• The show IP DHCP command can be used to display the current bindings and verify that the DHCP server is working correctly.
• The DORA process (Discover, Offer, Request, Acknowledgment) is used to verify that the DHCP server is working correctly.

Conclusion

• The demonstration showed how to configure a Cisco router to act as a DHCP server and verify that it's working correctly using a client.
• The same concept can be applied to other devices, such as a firewall, to implement DHCP services.

Learn how to configure a Cisco router to act as a DHCP server, dynamically assigning IP addresses to devices on a local network. This scenario is particularly useful for remote branch offices.