Question about IP

[toxicnos]

So the DHCP process is broken into 4 parts. 

 

1. The Discover this is when the client advertises on the network that is needs an IP.

2. The Offer, this is when the server checks it's pool and offers an available IP address to the client.

3. The Request, this is when the client verifies with the server that it heard correctly and accepts the IP address

4. The ACK, This is when the server acknowledges to the client that it's ok to use that IP. 

 

Typically a client gets a lease time of some period of time from minutes to days. This is the amount of time that the IP is valid for that client. Usually halfway through that lease the client asks if it can keep it for another lease period. For example with a lease time of 4 hours the client requests (Follows parts 3 and 4 above only) that it's lease be renewed. Usually this is fine and so the client is happy and the lease never expires. 

 

Other process like a PC reboot and disconnect and reconnect of the layer one media (wireless/wired), will cause the client to release it's IP and start over from step 1 above. This process is called a release. 

 

Now DHCP has many other options that can change how this works depending on the network and security you want to use. In the case of your ISP, they may have a process in place that when it sees a discover rather than a request (Step 1 rather than step 3) it sends out a NAK that tells any client using the IP address that it can no longer use it and it clears that IP from it's used table. It then acts as if your modem/router is a new client and stars the whole process from the beginning issuing you a new IP address.

Wow thanks, very informative! Thanks for explaining that to me.