[NTLUG:Discuss] philosophical dhcpcd question

[Paul Drew]

The DHCP Lease reservation system is just part of its working protocal. It 
tries to reduce network traffic by retaining the IP address for the given 
amount of time designated by the server. At 50% of the lease expiration it 
will attempt to renew the lease on its own before it loses the IP address. 
If it is unsuccesful it will attempt again st 75%, and then in more frequent 
intervals untill the lease expires, upon which it will drop the lease. The 
lease is set to allow the computer to be happy without polling the server 
for an IP address all the time.

The server tracks IP lease via mac address on your ethernet connection 
device. When you boot back up the server will just re-issue the same IP 
address to the matching mac address provided that another machine has not 
claimed it.

In a windows system most often I find that a machine will relinquish its 
leased IP address upon shutdown or reboot. This is so that machines the are 
not often on the network do not tie up non needed IP reservations. This is 
especialy useful when you have non private addressing, and a frequent number 
of personal changes with a limited amount of IP's.

The issue is how to determine if RedHat is supposed to release that IP 
address upon shutdown or reboot. If it's not you would need to script it to 
use those commands upon shutdown, and boot. I can't imagine it being that 
hard to implement. This would remove any redundancies and nuances when you 
are moving from place to place. I can sympathize because I travel everywhere 
with my machine, and I have to go from DHCP to static enviroments which 
allows me no recourse other than manual setup over and over.

The command "dhcpcd -k eth0" is the same as in windows "ipconfig /release", 
but this also depends on which version of windows you are running. I think 
you get the point though. :) It's just part of windows by default, and I 
just can't imagine why it wouldn't be default in RedHat. If it's not then 
just put it in as part of the shutdown process like you said. :) I hope my 
rambling helped you out some. Have a great day. :)

Paul Drew

>From: Fred James <fredjame at concentric.net>
>Reply-To: discuss at ntlug.org
>To: discuss at ntlug.org
>Subject: [NTLUG:Discuss] philosophical dhcpcd question
>Date: Wed, 14 Aug 2002 13:07:14 -0500
>
>Now that I understand that on reboot the DHCP client will attempt to 
>acquire the same IP it had before, I am prompted to ask why?
>
>BTW:
>Just issuing "dhcpcd -k eth0" as root in a terminal window, just before 
>shutdown, seems to have solved my particular problem (moving between work 
>and home and trying to pick up a good IP).  Earlier someone had asked if 
>both DHCP servers passed out IP's in the same range and I said yes because 
>that is what I had been told, but in asking about some numbers that didn't 
>fit with that explanation I uncovered the truth - they do not.
>
>--
>small is beautiful
>
>
>
>_______________________________________________
>http://www.ntlug.org/mailman/listinfo/discuss




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