DHCP Helper or Relay Agent Configuration in Cisco IOS
While working, I come across many networks where the DHCP server is configured in a machine which is located in a remote location, and from there clients in different locations (geographically) and different IP network, are getting their DHCP assigned addresses. This is done by using something called DHCP helper or relay agent. How DHCP relay agent works - DHCP messages are broadcast messages. They can not cross the boundary of a single IP network (broadcast domain). What the DHCP helper does - it converts the broadcast messages into unicast messages and forwards them to the remote DHCP server. When DHCP packets are going through different IP networks as unicast packets, we need only IP reachablity through routing only. For further reading - Understanding DHCP Relay Agents Now let's introduce our network first - DHCP relay agent network Here the PC will get it's IP address from the DHCP server. But DHCP client and server are located in different networks. The PC