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Old July 3rd, 2012, 10:28 AM
take2hikes take2hikes is offline
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Default Changing Router IP Address

Hi everyone, I am trying to change my routers public IP address.

If I connect directly to my modem and power cycle it, I can get a new address. But, if I connect the modem back to the router and power cycle it - no matter what I do I get the exact same IP address. In the router settings I have "Get Dynamically from ISP" checked. I'm not concerned with the IP address of my individual computer, as that is not a problem. But I am unable to connect directly to my modem with my laptop, so I am stuck with the address that my WNDR3700 keeps using.

My question is why it continues to pull up the same IP address. I've tried changing it statically and power cycling it, just in hopes that when I change it back to Dynamic it will get a new address. At the very bottom of the page it says "Use default MAC address" and that is checked. If the public router IP is related to the MAC address, will changing that to "Use computers MAC Address" change the public IP?

I've tried contacting Comcast (my ISP) who wanted $80 to remotely connect to my computer, and Netgear who also informed me I'm outside of their warranty. There has to be SOME way to change my routers public IP, please help!

P.S. I'm a computer science major, so I'm not clueless. If anyone has steps, just please provide them to me. Thanks!

.t2h
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  #2  
Old July 3rd, 2012, 01:10 PM
Alnico Alnico is offline
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Default Re: Changing Router IP Address

It's not quite clear from your post why it is important that you get a different IP on the router. Also, it is not quite clear if the addresses you are getting are private or public IPs.

Generally, if the ISP is uisng DHCP, DHCP will hold the IP address for the client's unique MAC address (PC attached to modem or Router attached to modem) until the lease expires. You can see the 'lease expires' period when you have the modem attached to a PC/laptop running Windows with the ipconfig /all command. If the MAC address facing the modem changes, and the ISP's DHCP server does not already have lease for that MAC then a new one may be assigned.

This is a moot point if your modem is in fact a router and offering up public IP addresses. I don't like such configurations as they often result in double-NAT and the issues tha come with it - so I configure my modem for pass-through.
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Old July 3rd, 2012, 02:35 PM
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jmizoguchi jmizoguchi is offline
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Default Re: Changing Router IP Address

Quote:
if I connect the modem back to the router and power cycle it - no matter what I do I get the exact same IP address. I
This is normal for cable modem. ISP will NOT renew the IP for longer duration so you will NOT able to change WAN IP at your will.

Only way to do that is to use Mac Spoof but you will run out of mac address to keep changing.

You will be wasting time on this matter specially comcast will keep same IP to it's mac address for minim 30days or plus
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Old July 3rd, 2012, 02:56 PM
take2hikes take2hikes is offline
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Default Re: Changing Router IP Address

To the first poster, I said my public IP address. I did not mention why I wanted to change my IP address as it is irrelevant.

To the second poster, I think that answers my question and explains why I can get a different IP for my devices but the router is specific.

Is there a method to changing MAC addresses?
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Old July 3rd, 2012, 03:03 PM
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jmizoguchi jmizoguchi is offline
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Default Re: Changing Router IP Address

Quote:
"Use computers MAC Address"
Like said, you will RUN OUT of mac address to do this. Most people keep asking about this issue are commonly block from forum that blocks it's IP etc.

You can not just magically come up with mac address for NIC, Each NIC has unique mac address assigned so if you have 4 PC then you can alternative change router to use it's mac address but if comcast will keep each duration for X amount of time/duration then you will some point will NOT able to get new ip address or depending on how cycle will work for you
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Old July 3rd, 2012, 06:49 PM
Alnico Alnico is offline
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Default Re: Changing Router IP Address

Fair enough, .t2h, you did say 'public IP' and I simply assumed by that you meant it was simply whatever was assigned to the device interface facing your modem - wethor the address was from a sanctioned public block or a private block - as either can be assigned to the external interface of the router depending upon wethor or not passthrough is used by the modem. My apologies if this came as anything else to you. Also, in my post, 3rd paragraph, I meant to say, "private IP". Unfortuantely, it was a long morning without coffee for me.

I asked about 'Why' you would need to do this because I have a duty, as a Certified Information Systems Security Professional, to protect the infrastructure. Rapidly changing your MAC address may cause a denial of service to you and other consumers and is not normal operation.

If I understood your ultimate goals I might be able to suggest a more approropriate workaround.
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Old July 3rd, 2012, 11:47 PM
jlewter jlewter is offline
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Default Re: Changing Router IP Address

Actually you can just make up a MAC as you wish.

I doubt any ISP's filter by the registering MAC.

Router web page.
"Basic Settings"
"Use this Mac Address"
Type in whatever you want. I would avoid 00 or FF as the first two digits.
You only need change the last two digits. After you do it then you may need to power cycle your modem.
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Old July 4th, 2012, 11:09 AM
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jmizoguchi jmizoguchi is offline
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Default Re: Changing Router IP Address

Quote:
Actually you can just make up a MAC as you wish.
True.. I was going to say too but I like to keep it basic in order complicate the issue and use wisely

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Old July 4th, 2012, 04:45 PM
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Default Re: Changing Router IP Address

I have a question for you guys, and feel free not to answer it

Can I use ABCDEFGHIJKLMNOPQRSTUVWXYZ as my MAC address?
Can I put - youransweriswrong - as my MAC address?

The simple truth is neither of the above examples will work, so you can't actually make up a MAC as you wish, there are rules that must be followed, and reasons those rules exist - yes, if you know the basic rules you can create a completely ficticious MAC address, but you do so at your own risk.

There's a time and a place to use MAC spoofing, and there are reasons why it should not be done.
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Old July 4th, 2012, 04:47 PM
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jmizoguchi jmizoguchi is offline
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Default Re: Changing Router IP Address

Quote:
Can I use ABCDEFGHIJKLMNOPQRSTUVWXYZ as my MAC address?
Can I put - youransweriswrong - as my MAC address?
funny man... figure rest new the what mac address should be..
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