Table of Contents
What is a DHCP packet?
A DHCP Discover packet is similar to the analogy above. When a device needs to obtain an IP address, it sends the DHCP Discover packet to the broadcast IP address 255.255.255.255. Packets sent to this IP address are received by all hosts on the network, and is used in this case to try and find the DHCP server.
How does a DHCP relay work?
The DHCP relay agent operates as the interface between DHCP clients and the server. The DHCP Relay Agent relays DHCP messages between DHCP clients and DHCP servers on different IP networks.
Why is DHCP relay needed?
The DHCP relay agent is any TCP/IP host which is used to forward requests and replies between the DHCP server and client when the server is present on a different network. Relay agents receive DHCP messages and then generate a new DHCP message to send out on another INTERFACE.
Why would a DHCP relay be needed?
A DHCP relay agent is a host or router that forwards DHCP packets between clients and servers. Network administrators can use the DHCP Relay service of the SD-WAN appliances to relay requests and replies between local DHCP Clients and a remote DHCP Server.
What is DHCP relay used for?
What is the purpose of DHCP Discover packet?
A DHCP client sends DHCP release packet to server to release IP address and cancel any remaining lease time. If a client address has obtained IP address manually then the client uses a DHCP inform to obtain other local configuration parameters, such as domain name.
What is a DHCP Discover packet?
The DHCP section identifies the packet as a Discover packet and identifies the client in two places using the physical address of the network card. Note the values in the CHADDR field and the DHCP: Client Identifier field are identical.
What is the purpose of DHCP relay?
How to configure the device as a DHCP relay agent?
The ip helper-address command configures the device as a DHCP relay agent. The DHCP relay agent forwards DHCP requests and replies between clients and servers when they are not on the same physical subnet. In the following figure, we have configured R1 as a dhcp server and R2 as a dhcp relay agent.
What are the benefits of DHCP relay agents?
Configuring dhcp relay agents helps to reduce the number of dhcp servers on your networks, making the task of IP address mangement less complicated. For this lab, my core router is going to be configured to serve as a dhcp server to the two local area networks attached to site1 and site2 routers.
How do I capture packets from DHCP server?
You will need to set your packet capture tool to download file to PCAP file and capture for 60 seconds. If your DHCP server is connected to the same switch you will want to capture off the specific port the client is connected to instead of the uplink. 3. Start capture. 4.
How does DHCP work on a switch?
The server replies with a unicast DHCP offer to the router offering the unleashed IP address. In return, the router broadcast the DHCP Offer message to the network which has sent the DHCP request. The broadcast message is received by a switch as shown in the above figure. The switch broadcasts the DHCP offer message to the hosts.