Red Hat

Hi All,

Could you please explain the purpose of assigning the static IP by using the DHCP Concept. Like by using the clients MAC address we assign the static IP Address. Waiting for your reply. Thanks in Advance.

One reason is ease of IP address management

Not sure I would agree with ease of ip address management. After all depending on how large the network is using dhcp to staticly assign ip addresses could be a very large task and if you are going to use static that way why not remove DHCP ahs assign everything it's own ip address.. I would say it is used for devices that need to have a staic ip address on a HDCP network. For example a printer or server or IDS system. Usually on a dhcp network you are only going to have a hand full of staticly assigned addresses.

You could do static for every device and every host... but do you a have a good way to automate such for every OS and device? This is why bootp style auto addressing is perhaps a good idea.

Just saying...

Problem sort of goes away with IPv6... (depending... those dhcp servers hand out a lot of data that isn't necessarily related to getting the device onto the network)

Devices which provide services might would need a static ip.
I can't say much for what you'd assign them for, but I know for sure it is better to assign static addresses by DHCP than on each client. Say your network gets larger and you need to split it into subnets, it would suck going around to all the machines to change them.

Here is the thought process;

DHCP is use for mobile devices which could/do move around form one network to another, i.e., Laptops.

Static is used for device that would not move around, i.e., Servers, Desktops and Printers.

If your network is growing then any new device that is static would get a static IP address for the new network. Mobile device connecting to the new network would get a DHCP address from the new network.

I guess if you are working for Mom & Pop you don't need to think this way but in an environment of 6000+ employees and 10000+ devices, using DHCP for static is not going to cut it.

Here is another thing to think about. Just because you map an ip address to a MAC address doesn't mean the machine is going to be assigned to that device. MAC spoofing ring any bells? This is why you want devices that provide a serves to have a static IP Address not some sort of DHCP static.

At the end of the day it all comes down to what you prefer. I prefer static devices to have static addresses and mobile devices to have DHCP addresses. If you cannot see far enough into the future to plan ahead for a growing network.......

We have to build thousands of PC's where I work. They are all built with the same image and thus they all use DHCP. A very few of them need a static IP (or at least the owners think they do ). We assign these static IP's but the PC's still use DHCP. We have almost 3,000 PC's but less than 100 of them have static IP addresses.

The usual genuine reason for assigning static IP's is security. My PC has a static IP address and that address is known by various highly secured servers. Thus an ssh from my PC will be accepted.

At home I use static IP addresses because I feel like it. But my roku box must use DHCP, it has no capabilty to enter an IP address directly. This is the only device I know that must use DHCP but I guess that others may exist.