Given what you have learned on DHCP, discuss the pros and cons of having a DHCP server on each and every network segment versus having some network segments receive IP address assignments over a router using DHCP relay agent.

DHCP is a network management protocol used on udp/IP networks where a DHCP server dynamically assigns an IP Address and other network configuration parameters to each device on a network so they can communicate with other IP networks. It enables computers to request IP address and networking parameters automatically from the Internet service provider ISP reducing the need for a network administrator or a user to manually assign IP addresses to all network devices In the absence of a DHCP server, a computer or other device on the network needs to be manually assigned an IP address, or to assign itself an APIPA address, which will not enable it to communicate outside its local subnet.

How DHCP WORKS

Have you ever used a printer that’s connected to your local network are you wondering how it keeps its network assignment every device on the network has a MAC address you can assign a static IP at the server to a specific MAC address this allows the network printer to always get the same IP even after it reboots and without assigning the IP to the printer if you print the network configuration at the printer, it will probably tell you that DHCP is enabled and no static IP is assigned. That’s because the IP assignment is handled at the server.

Pros:

All the IP configuration information gets automatically configured for your client machine by the DHCP server.

If you move your client machine to a different subnet, the client will send out its discover message at boot time and work as usual. However, when you first boot up there you will not be able to get back the IP address you had at your previous location regardless of how little time has passed.

DHCP is easy to implement and does automatic assignment of IP addresses to requesting clients. Hence manual configuration time of IP addresses can be reduced.

The implementation does not require any additional costs.

Duplicate or invalid assignment of IP addresses are prevented. Hence there is no chance of conflicts in IP addresses.

It simplifies administration of the network.

It supports multiple scopes e.g. multicast scope, super scope etc.

It has great benefit to mobile users as valid configuration parameters are automatically obtained from the new network.

Cons:

DHCP server can be single point of failure in networks having only one configured DHCP server.

DHCP packets can not travel across router hence relay agent is necessary to have DHCP server handle all leases on both network segments. Relay agents receive broadcast DHCP packets and forward them as unicast packets to DHCP server. Here relay agent must be configured with IP address of the DHCP server.

Security: As DHCP server has no secure mechanism for authentication of the client, it can gain unauthorized access to IP addresses by presenting credentials such as client identifiers which belong to other DHCP clients.

The machine name does not change when new IP address is assigned.

Client is not able to access the network in the absence of the DHCP server

More About DHCP:

DHCP server defines a scope, or range, of IP addresses that it uses to serve devices with an address. This pool of addresses is the only way a device can obtain a valid network connection.

This is another reason DHCP is so useful - because it allows lots of devices to connect to a network over a period of time without needing a massive pool of available addresses. For example, even if only 20 addresses are defined by the DHCP server, 30, 50, or even 200 (or more) devices can connect to the network so long as no more than 20 are using one of the available IP address simultaneously.

Because DHCP assigns IP addresses for a specific period of time (a lease period), using commands like ipconfig to find your computer's IP address will yield different results over time.

Though DHCP is used to deliver dynamic IP addresses to its clients, it doesn't mean static IP addresses can't also be used at the same time. A mixture of devices that are getting dynamic addresses and devices that have their IP addresses manually assigned to them, can both exist on the same network.

Even an ISP uses DHCP to assign IP addresses. This can be seen when identifying your public IP address. It will likely change over time unless your home network has a static IP address, which is usually only the case for businesses that have publicly accessible web services.

In Windows, APIPA assigns a special temporary IP address when the DHCP server fails to deliver a functional one to a device, and uses this address until it can obtain one that works.The Dynamic Host Configuration Working Group of the Internet Engineering Task Force created DHCP.