How do I change my IP address -- that it is "never" the same

I saw this on an old post:
As to your question beforethefall, if you have a router you could set it to assign a differnt IP each time you connect.

If you don't have a router there is another way, but it requires several restarts and is some what complicated if you don't know what you're doing.


My question is how do I do that? I have a "wired" linksys router and am at the admin website - is it simply having WAN connection type reflect "obtain IP automatically "?

 

Hmmm - what I want is a way for my IP address to automatically change not simply renew the same one it has.

 

Since you are behind a router, there are two IPs involved:

The one assigned by your ISP. This is the one your router adopts as its WAN IP address.

The one assigned your workstation by the router. This is your LAN or NAT IP adddress.

There is no earthly reason to need a change in the latter IP address. No one outside of your home or office ever sees it. That IP cannot be used on the internet, it would never work.

The only IP that the internet sees is your WAN IP used by the router. To change this IP:

Unplug the router.
Unplug the modem.

Wait at least five minutes.

Plug in the modem.
Plug in the router.

Reboot all computers.

Now how do you check that the WAN IP has changed?
I wrote you a little script to do just that:

 

The IP address applied to the external port of your router is assigned by your ISP. They will have a DHCP server that assigns your IP when you connect. The key property that controls how long your connection keeps that IP address is the lease period. The lease period is set at the DHCP server and is therefore out of your control. Most ISP will set this at a very short period so that each time you connect, you are assigned a different IP address.

So as Bill describes, to change the IP you need to disconnect and then reconnect the router as this will force the system to renegotiate an IP address from the DHCP server.

However, not all ISPs work this way. The obvious example being many ISP set up to service small business, where they will configure their system to provide static IP addresses.

If reconnection doesn't change the IP for you, I think you will have to contact your ISP, as the problem is likely to be specific to their configuration.

 

Marvelous! Thank you - it worked perfectly.

 

Many DOCSIS cable modems require that they be unplugged in order to pull another IP address. Just turning them off with the switch in the back does not work; they retain their settings, and an active reset sequence is not performed by the cable system when they are turned back on. The RCA series is notable for doing this.

 

It is possible your cable system is NAT'ing to preseve IPv4 addresses.
It is highly unusual (and not very desirable for the cable system) to pre-reserve address space by MAC addressses.
If you do a WHOIS on your IP does it return a true public IP space owned by your cable company?
Authenticate by MAC, yes. Reserve and assign precious IP addresses by MAC makes no sense for the company unless it is NAT'ing.

Fortunately this is not happening with the original poster.

Regards.

 

Most DHCP servers will try to reassign the same IP address to a client MAC address if the IP address is still available. Perhaps you have an ISP who has enough IP addresses that they aren't reused as soon as they are released.

However, I think ISPs also have a method of assigning IPs based on log on or an ATM layer 2 equilvalent to MAC.

 

Changing IP

My suspicion is that the dhcp server on your broadband network assigns the ip.
If the mac address of the network card is changed the service would think that you are another computer and assign a new ip.
You could do this with a new network card.
Alternatively you could clone the mac address if your Linksys router has that ability. With some routers you can set the mac address in the cloning area . Even changing one digit will do it.
Best to unplug your isp modem for a while while doing this procedure.
That way there is a higher chance that the network will see you as a new device and assign you a new ip.
Of course you can check your current or no ip in the standard ways.

 

Changing Your IP Using a Router

Interesting question that always seems to come up.
Is someone trying to track you ? Paranoid ?
First question do have dsl or cable broadband.
With DSL you dial in . Each time the ISP gives you a new ip.
You could disconnect your connection in the router control panel and reconnect same way.
The ISP will assign you a new IP.
With cable broadband there are 2 scenarios.
With the more common the ISP assigns an ip based on mac address on a fairly frequent basis. Most routers have a "clone the mac address" feature in the router control panel with some lame explanation about some isps require you to register your mac address and this way you can continue your internet use without a skip of a beat. LOL . With this feature not only can you clone the router to be the mac address of the network card used but you can change the apparent mac address to anything you want. All you have to do is change one single digit or more. It is best to unplug the modem wait a period of time ( 10 minutes is usually sufficent ) plug in the modem and router . The network will see a new device and .....
However in some discussion elsewhere it was noted that some cable ISPs assign ips in a diffirent manner and that these ip last for a number of months .
You can always go to a library or hotspot at the worst .

 

This statement is just not true as a general statement of fact for ADSL.

I mentioned NATing of IPs to conserve IP address space. This is very common in PPoE ADSL.

In addition, many local offices deliberately allow relatively long lease times for DHCP assigned IPs. This is to meet TOS terms in the case of brief interruptions.

I have had Verizon/nee Bell Atlantic DSL service since 1996. In that time I have had maybe 3 IPs.

I do not have a static IP assignment. The only time my IP changes is if I disconnect for at least three days. The DSLAM does not have a very large pool of free IPs to assign, so the lease on the IP is one week.

 

It was not very crowded at the CO I admit.

The bandwidth was nothing compared to what is available now. I think it was 384/64 service.