Why do my local network ip addresses keep changing?

[Tim Bogart]

The original reason for using DHCP (for the MOST part) was limited access to IP 
addresses.  Most people (including network people) had never even heard of 
NATting or private IP's (10.x.x.x or 192.168.x.x).  Conservation of IP's was 
desirable.  You could plan on a certain amount of absenteeism from your work 
force, so 100 people could get away with using 90 or 95 IP addresses.  Now we 
don't need to do that, especially with IPv6 (two additional octets to the right 
of the ip).  Now folks don't have to even deal with DHCP in most circumstances, 
but do so out of habit.  Save yourself the headache of administering DHCP and 
just go static.  I've seen offices of 5 people set up for DHCP by some MCSE (you 
know what that stands for don't you?  Must Consult Someone Experienced!)  This 
is what I call "The ABSOLUTE ZENITH of ABJECT ABSURDITY (running dhcp services 
for 5 people).  It's just another thing to break.  So, get rid of it.  It's FUN! 
 It's EASY!  And it TASTES GOOD TOO!!!  (please excuse my lame attempt at 
humor.)

My $0.02

Tim





________________________________
From: Eric Shubert <ejs at shubes.net>
To: plug-discuss at lists.plug.phoenix.az.us
Sent: Fri, October 1, 2010 6:19:26 PM 
Subject: Re: Why do my local network ip addresses keep changing?

Stephen wrote:
> you have two options either use static assignments in whatever you use
> to assign DHCP so it will always give Mac address X Ip Y

This is the method I prefer. I call this a 'fixed' address (as does IPCop), as 
DHCP is still used to obtain an address, routing and DNS information (so it's 
not what's commonly referred to as 'static', which is configured on each 
computer), but each computer ends up with a fixed, or unchanging, address.

The way this is done is by modifying the DHCP server's settings. Some DHCP 
server's configuration settings (web pages) allow this feature to be used, and 
some do not allow for it. It all depends on the router (assuming here that your 
router is also your DHCP server) you are using. In your router's configuration 
(web pages), look for the DHCP Server settings. If you can find a place for 
specifying fixed leases (a MAC address and IP address together), this is where 
you'll add each computer's MAC address, along with the corresponding IP address 
you want assigned.

If your router doesn't allow for fixed leases, you'll need to configure each 
computer individually, giving each one a static IP address, along with gateway 
and DNS addresses. The gateway address is the address of your router. Your DNS 
addresses will be assigned by your ISP, and should be obtainable from your 
router's configuration. Look at the WAN interface status/configuration for DNS 
addresses. These addresses will be the same for all your computers, as well as 
your router.

If you have difficulties, please post the make/model of your router (or better 
yet a link to the user manual for it), and we can help you out.

HTH.

> or to
> configure your devices with static IP's
> 
> This is the nature of DHCP and it works they way by design.
> 
> 3rd alternative is to set a DHCP lease so effing long that it
> essentially never expires. but i am a larger fan of DHCP assignments.
> 
> On Fri, Oct 1, 2010 at 5:04 PM,  <joe at actionline.com> wrote:
>> I have four computers on my local network, 3 of which access by wireless.
>> While most will go along working fine for a while, occasionally the ip
>> number changes on some of them.
>> 
>> Why does that happen and is there any way to prevent that or to be able to
>> reset the ip# back to what it was?
>> 
>> 
>> 
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> 
> 


-- -Eric 'shubes'

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