What is the point of Leasing out IP addresses?

[aquaboy1976]

I'm learning DHCP right now and I read about IP leasing, it didnt explain the benefit of leasing IP addresses though. Can someone please help. Thanks in advance!

 

[GiaBetiu]

Do you mean why they are not assigned forever?
This is the convention. A workstation will have a ticket. A service is providing that ticket. The ticket has a valability.
In this way it is easy to manage. You can set a long life for them, or a short one.
Plus, the DHCP server service should know what is the situation. As you know, the client is checking its lease availability before it will expire. This is a confirmation that that computer still exist, and it still has the right to be in that network.
If you are using a dynamic DNS then DHCP registering is really valuable. When a computer is receiving a lease it's IP address will be recorded in DNS.
Gia Betiu
m.betiu@chello.nl
Computer Eng. CNE 4, CNE 5

 

[aquaboy1976]

Right, I was asking why IP addresses are not assigned forever. Thanks for the explanation too, it really helps.

 

[merlinx]

DHCP has the advantage that you can administer the IP/DNS/&Such addresses without going to each workstation, also helpful if you have dial in clients. If you use a gateway for Internet, DHCP is a good as far as the DNS servers are concerned. One of the disadvantages is when the DHCP service fails, Running tickets will work and the rest will have network problems. Depending on the protocols installed, the computers will have no network niehborhood or minimal availabilities. If you search this site with the keyword dhcp, you can see what happens when this service fails.

You can setup your network so that selected users or devices have an IP and the rest use DHCP.

Your DHCP server/device IP will end with 1 : xxx.xxx.xxx.001

If you decide not to use DHCP for some or all of the network, then you should write a logon scripts which can change IP/DNS/DHCP/&Such things for you. If your DHCP service stops working then you can compensate during the down time using the different logon scripts.

I hope this helps a bit in getting started.

 

[dankelt]

spalzitch,
I can give you an example why I don't want IP address leases to last forever. I work for a VAR, so we get computers coming in and out of here quite often. When we put them on the network they get an ip from the DHCP server, then when the PCs are taken off then network, I want that ip address to free itself after so much time. If it didn't I would run out of addresses pretty quick.
Same goes with ISPs, especially dialup ones. There is no way an ISP could give each customer it's very own IP address.

merlinx,
Your DHCP server/device IP will end with 1 : xxx.xxx.xxx.001

Huh?

 

[merlinx]

Dankelt,

many hardware devices, ( firewalls, win98 internet sharing, and many others), demand 001.

Just an info...

 

[merlinx]

update :

not (win98) but (win2k)

 

[dankelt]

The fact that Windows ICS defaults to 192.168.0.1 has nothing to do with the fact that it is a DHCP server. It's just something Microsoft did to keep ISC simple. Same goes with hardware firewalls.

You may want to read up on RFC 1541.

 

[merlinx]

2k terminal demands 001 for sharing, netgear firewalls for dhcp also. rfc 1541 > 2131 > 3396. None the less, if a single maschine wishes a paticular IP and everything else is flexible, no problem.

 

[dankelt]

Yes, you are correct, ICS sets your local interface to 192.168.0.1. ICS is basicly a simple wizard to set up NAT. If you set up NAT manually you can set your IP address to anything you want. I still don't understand what that has to do with DHCP.

Maybe I am misunderstanding your posts...???

 

[merlinx]

Dankelt,

If I could go back and correct my post, NAT/Internet/Gateways would be the nouns I forgot to include. Now I understand your comment better, Thanks for the correction. Yes the systems in question included NAT.