Central DHCP server
Head office router R2 is the DHCP server for every branch; it already has a pool for this branch's LAN (192.168.10.0/24) and a route back to it. The PCs on R1's LAN get no address. Make R1 pass their requests to R2 (10.0.0.2). Then the internet provider asks you to take R1's internet address on Gi0/2 from their DHCP server.
How it works: this is VulnTech NetLab, a network simulator running in your browser. Click a device in the diagram to open its console and type commands, just like on real equipment (? shows help, Tab finishes a word). Click a cable to inspect it. Tasks tick themselves off as you complete them; questions are answered in the box under each task. Your work is kept if you reload; Reset starts the network over.
Solution explanation
The helper address goes on Gi0/0, where the clients' broadcasts arrive. R1 forwards them to R2 as unicasts with giaddr 192.168.10.1, and R2 chooses the pool whose network contains that address. ip address dhcp makes Gi0/2 a DHCP client: it got the first free address in the ISP's pool (203.0.113.10) and a default route to 203.0.113.1.
Show solution
[R1]
enable
configure terminal
interface g0/0
ip helper-address 10.0.0.2
interface g0/2
ip address dhcp
end
show ip interface brief
[PC1]
ipconfig /renew
ipconfig /all
[PC2]
sudo dhclient eth0