[NTLUG:Discuss] philosophical dhcpcd question

[Fred James]

OK, but why?  Please understand that this is not a question of how it 
is, or what happens, nor am I suggesting the world change to fit my 
current whim.  It fairly is easy to understand why we might want a DHCP 
client to try to retain a single IP for the duration of its connection, 
or possibly even upon reestablishing a failed connection, as long as it 
is connected to the same DHCP sever.  But is there any reason to want 
that DHCP client to try to keep the same IP it had before power down, 
when it is powered up connected to a different DHCP server?

Paul Drew wrote:

> 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
>>
>>
>>
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-- 
small is beautiful