Forcing Comcast ISP to New IP Address With Router and PC

Slow Speed Broadband Connections With Comcast Are Not The Norm

If you are experiencing slow speed broadband internet problems, or you are a WoW gamer, and your World of Warcraft connection has excessive lag, then you may have the following IP problem with Comcast ISP or your Cable or DSL Internet Service Provider.

There does seem to be a situation that occurs from time to time with Comcast high speed Internet service that is very peculiar. It seems as though some of the IP addresses provided by the automatic DHCP configuration at Comcast produce a very slow Internet connection. Getting a new dynamically generated IP address from the Comcast system can help improve your connection upload and download speeds issue. Learn how you can do this easily with a wired or wireless router and your computer.

So, what do I have to do to change the IP address assigned to me by my Internet service provider?

Change Your IP Address: Quick Summary Answer

To get a new IP address, start by cloning another computer’s Mac address using a router hooked up to the cable modem. Then reboot the cable modem, and if everything went OK, the ISP provider’s DHCP system will assign another IP address for your Internet service automatically. Read the IP address change details below.

Test your Internet speed using any one of the modem speed tests online. Then check your IP address using the check my IP address websites. Write both of these down to use later for comparison purposes. Note: The source website server is also a factor for upload and download speeds to your computer. So, it’s also a good idea to note this source website server from the modem speed test, for checking your online upload/download speeds in later comparisons.

Understanding the technical terms
IP address Types (Dynamic and Static)

There are two types of IP address that can be assigned. Dynamic and Static. When a computer is configured to use the same IP address each time it powers up, this is known as a Static IP address. In contrast, in situations when the computer’s IP address is assigned automatically, it is known as a Dynamic IP address.

Sticky Dynamic IP Addresses

A sticky dynamic IP address or sticky IP is a term created by cable and DSL users to describe a dynamically assigned IP address that does not change often. This is however an informal term, as a sticky IP does not differ in any way from other dynamic IP address. Most cable and DSL ISPs assign dynamic IP addresses. However, if you have Comcast Business Internet Service Class with a static IP address or have requested and pay for a static IP address with your home Internet service provider, the only way to change this is for Comcast, other cable companies, or DSL service providers to do it on their end.

Even though IP addresses may not change often for cable or DSL users, the addresses are still controlled by the standard DHCP process. Since the modems are often online for extended periods of time, the leases on the IP addresses are commonly renewed, and therefore may not change.

Dynamic Host Configuration Protocol (DHCP)

The Dynamic Host Configuration Protocol (DHCP) automates the assignment of IP addresses, subnet masks, default gateway, and other IP parameters. There are four modes of operation: dynamic allocation, automatic allocation, static allocation, and manual allocation.

  • Dynamic allocation: A network administrator assigns a range of IP addresses to DHCP, and each client computer on the LAN has its IP software configured to request an IP address from the DHCP server during network initialization. The request-and-grant process uses a lease concept with a controllable time periods, allowing the DHCP server to reclaim (and then reallocate) IP addresses that are not renewed (dynamic re-use of IP addresses).
  • Automatic allocation: The DHCP server permanently assigns a free IP address to a requesting client from the range defined by the administrator. This is like dynamic allocation, but the DHCP server keeps a table of past IP address assignments, so that it can preferentially assign to a client the same IP address that the client previously had.
  • Static allocation: The DHCP server allocates an IP address based on a table with MAC address/IP address pairs, which are manually filled in (perhaps by a network administrator). Only requesting clients with a MAC address listed in this table will be allocated an IP address. This feature (which is not supported by all routers) is variously called “Static DHCP Assignment” (by DD-WRT), “fixed-address” (by the dhcpd documentation), “DHCP reservation” or “Static DHCP” (by Cisco/Linksys), and “IP reservation” or “MAC/IP binding” (by various other router manufacturers).
  • Manual allocation: The DHCP server does not assign the IP address; instead, the client is configured with a user-specified static IP address.

Many DHCP servers can manage hosts by more than one of the above methods. For example, the known hosts on the network can be assigned an IP address based on their MAC address (static allocation) whereas “guest” computers (such as laptops via WiFi) are allocated a temporary IP address out of a pool compatible with the network to which they’re attached (dynamic allocation).

How do I get a New Comcast Dynamic IP Address?

The following Comcast IP address change process is for dynamic addresses. If you have a router installed after your Comcast modem, then this next procedure is very easy to get the Comcast system to dynamically generate a new IP address. If you do not have a router, I strongly suggest you get one to have an extra firewall between your computer and the Internet. Most IP addresses given out by the Comcast DHCP system are in a leased mode. This means that if your modem is turned off for several days or more, the IP address goes back to a group of IP addresses to be automatically reassigned to other users. Turning off the modem for short periods of time will not reset the leased IP address because the modem is assigned the IP address based on the original computer’s MAC address. Every type of networking hardware has a unique code that is the Media Access Control address or MAC address for short.
Linksys Router Clone Mac Address

Linksys Router Clone Mac Address

Router’s also have a MAC address. Once this MAC address is synced up with the cable modem, the Comcast DHCP system assigns the IP address to the online outlet. However, if the MAC address is changed, the Comcast DHCP system assigns a new IP address to the online outlet, because it thinks it is a different location. Each computer, with a network card, also has unique MAC addresses. If a person were to hook up a different computer directly to the cable modem, it is likely that a new IP address would be assigned by powering down and then up again the cable modem. However, with a router it is much easier to assign a new MAC address to the router itself. Most routers today have what is referred to as clone the MAC address. This feature allows the user to make the router look like any one of the computers that reside on the premises. Simply logging into the router through a web browser by typing for Linksys or Cisco, or do a search for Router IP Address to find your particular brand.

linksys-router-setup Routers Login IP Addresses – Use The Following Format 192.168.x.x

Click on those links above to try logging into your router. Those specific router links will open in a new window or tab, or right click from your browser to open in a new window or tab so you can follow the instructions at the same time you log-in to your router. Here is a PDF document link to brand and model specific default router information list of Manufacturers, Models, User Names, Passwords, and Default IP addresses. Note, before attempting this procedure on your router, I suggest you print this information out for reference. Use the print button from the permanent link to this how to get a new IP address article. Also note that a router’s IP address can also be changed too. If you can’t get a log-in screen on your browser, then you aren’t getting to the router’s proper IP address for your local area network. Also try logging in to your router with a different browser like Firefox, Google Chrome, Safari, Internet Explorer, Opera, Camino, SeaMonkey, Flock, and others. If that doesn’t work, then do a Google Search for your particular router brand and model number IP address. If after finding the correct IP address for your router, but still can not get a login screen prompt, you might have to do a hard reset of the router’s firmware settings (usually a recessed button). However, if and when you do this, the router will revert to the defaults, and you will loose all your custom user name, password, wireless settings such as SSID and encryption codes, along with other TCP and UDP port settings that might be assigned for online game hosting like WOW – World of Warcraft private servers, if those online gaming TCP and UDP port settings were customized by you or someone else to begin with. After doing a hard router reset, you would then have to re-enter all the information again.

After you get to your router’s IP address and you have a user name and password prompt, then type in the login name and password. Hopefully you have changed the user name and password for security purposes (and wrote them down) when you first set up the router and changed them from the default settings. The browser is your window into the router’s operating system and allows you to login and set up the router using the internal configuration program. Find the area of the configuration program (usually a tab or hyper-link) where you can clone your MAC address and perform a clone to a new MAC address. Before you clone the MAC address, write the current MAC address down. This is so you can put it back to the original if you need to. Once the cloning of the MAC address is done, then you can try a release IP address and renew IP address in the router’s programming structure. This sends a release the lease to the Comcast DHCP and then renews with a new IP address. Suggest powering down the cable modem, router, and computer at this time. Then re-power everything back up and you should have a new IP address.

Now go back and check to see what your current IP address is and the speed at which you can upload and download from the Internet using the online modem speed test. Hopefully you are now running at light speed and no more WoW lag for the active gamer.

Good luck.

Contact Jim for your online business solutions. Professional Internet marketing services for your B2B or B2C business today. Get your website found online and start getting more customers now.

PS This particular problem I have personally seen, and have been able to rectify Internet connection speed issues using this technique. This may not be your particular problem, but it’s worth a try. This new IP address solution might also work for other high speed broadband ISP providers. Give it a try with your Internet Service Provider and let our readers know if it works for your DSL or Cable ISP company.

Jim Warholic

OK Anonymous, good point.

So, what do I have to do to change the IP address assigned to me by my Internet service provider?

Here is how to change you IP address in a quick summary answer.

It starts with a MAC address that is assigned to the router or computer that is hooked up to the cable modem. Clone to another computer's Mac address using a router hooked up to the cable modem. Then reboot the cable modem, and if everything went OK, the ISP provider's DHCP system will assign another IP address for your Internet service automatically. Read the IP address change details above.

Jim Warholic

OK Anonymous, good point.

So, what do I have to do to change the IP address assigned to me by my Internet service provider?

Here is how to change your IP address in a quick summary answer.

It starts with a MAC address that is assigned to the router or computer that is hooked up to the cable modem. Clone to another computer's Mac address using a router hooked up to the cable modem. Then reboot the cable modem, and if everything went OK, the ISP provider's DHCP system will assign another IP address for your Internet service automatically. Read the IP address change details above.


This is done with just 1 computer? The same computer I’m already using?

I’m a bit confused. If there’re multiple computers involved, could you please detail the steps at what point each are used? Also, at what point do I press the reset button on the modem (as opposed to rebooting it?).

Jim Warholic

I’ll try to simplify this a bit.

It can be done with one computer and a router. Or, it can be done with two or more different computers and/or a router.

In essence, another computer or a router provides a different MAC address than the one that was originally supplied to the Comcast modem. This new MAC address triggers a new IP address from Comcast when seen from the Comcast DHCP system.

Using the router to clone the MAC address of another computer on the Intranet will then be seen at Comcast as a different computer, thus generating a new IP address.

I suggest that once the MAC address is cloned to the router from the other computer, then reset the modem using the reset button. Also, your router can be rebooted at the same time.

Before you do any of this, I recommend searching on Google for “What is My IP Address” and writing your current IP address down. Then make the changes and check your IP address again.


Thank you for responding so quickly, Jim. I appreciate it.

I believe I understand clearly now. However, after trying, I still have the same IP address.

1. My ISP is Comcast and I’m using one PC and one router

2. I do have a dynamic IP address

3. I have a Belkin Router

4.I went in the Belkin Router and clicked the “Mac Address” tab.

5.I clicked the clone Mac address option (after writing the original numbers down).

6.My internet connection dropped immediately – presumably as a result of the Mac address cloning.

7.Then, as per your instructions, I powered everything down and after 5 or so minutes I turned everything back on.

8.Internet is working again

9.IP address is still the same

10.Mac address in the router is the new cloned one.

Any further help you could provide would be greatly appreciated.
Thank you for your time.

Jim Warholic

First off, I suspect that you cloned the same MAC address that you originally had with the computer to begin with, and this MAC address was logged in to your ISP provider.

You actually need to generate a different MAC address than what you had. Note that there are some programs available that can generate a random but valid MAC address. These programs are sometimes called MAC address spoofers. I can not vouch for any of these software programs. Note that not all MAC addresses are valid, and the system seems know which MAC addresses are valid and which ones are not. Once a MAC address is generated, and if the router is between the computer and the cable modem, you would need to enter the new MAC address manually into the router and then completely reboot the router, and then reset the cable modem from the reset button. Turning off the cable modem and turning it back on does not necessarily completely reset the modem.


It worked for me! Thanks for posting these instructions.

First I called comcast a couple times and asked if they would reset it. They reset the modem but the ip remained the same.

Then I hooked the modem directly to a laptop instead of thru a router and got a new ip address. When I plugged the modem back into the router it registered with the orignal ip address.

At that point I followed the instructions. Entered in made up numbers in the mac clone blanks and released, renewed, reset the modem, release & renewed again and then had a totally different ip.


Lol I have to say, I completely overlooked/forgot resetting the modem at the SAME time as cloning the MAC address of my labtop haha. I was scratching my head for about 40 minutes or so saying to myself “why the h— isn’t this working like the last time I did it” before I came across your site and just busted out laughing at something so minor I screwed up. Gotta love reading a dozen “only way you can reset your IP is by calling Comcast” posts when I already knew there was another way to reset it.

So for saving my head another headache and from saving my eyes from another “Call Comcast to reset your IP” I have to thank you again ^^

Hope all is going well for you =D


Jim, thanks for this info. But I remember having to call Comcast and telling them my MAC address so that I could begin service. Am I interpreting this correctly as that Comcast give service to an “activated modem” regardless of it’s MAC address? Then I wonder how Comcast “knows” who is who, for example, when they are subpoenaed. It’s apparently not by matching IP’s and MAC addresses?

Jim Warholic

Hi John,

There are a couple of clarification points here to consider.

Most devices, probably including the modem itself, have MAC addresses. A Media Access Control address (MAC address) is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies including Ethernet. Logically, MAC addresses are used in the Media Access Control protocol sub-layer of the OSI reference model.

I say above, probably including the modem itself, has a MAC address, though I am not absolutely sure on that one. However, I do know, that the modem itself is registered with Comcast, with some unique identifier, which is tied to a particular physical address location. Now, the way the Comcast DHCP server assigns IP addresses seems to be dependent on the end user’s MAC address of either a computer hooked up to the cable modem, or an attached router assigned MAC address, which triggers the Comcast DHCP network server to assign an IP address. This IP address seems to be assigned in a lease arraignment, relative to the MAC address and the cable modem. On receiving a valid request, the server assigns the computer an IP address, a lease (length of time the allocation is valid), and other IP configuration parameters, such as the subnet mask and the default gateway. In essence, I suspect Comcast keeps track of all the IP addresses that have been assigned to the particular cable modem, and the dates of when those IP addresses were assigned.

So, what happens when you assign a new MAC address, the DHCP server at Comcast assigns a new IP address. Sometimes, if you switch back to the old MAC address, before the IP lease is up, and before the IP address is reassigned to someone else, the DHCP server at Comcast will reassign the old IP address to you.

So, the bottom line is, in my opinion, there are cross-reference times, MAC addresses, and IP addresses that can track you online no matter what. It all depends on how long Comcast or any other internet service provider keeps this information on hand. The information would have to be subpoenaed though.


Do you have any experience with Comcast Business class service?

They assigned a ‘dynamic’ ip address the day i started and i can’t get it to change for the life of me.

I have an SMC business gateway cable modem which allocates dynamic addresses (dhcp) within the dmz at addresses.

I started with a single computer in the dmz and tried to change it’s mac, but that’s pretty hard. So I bought a wrt54g and placed it between my laptop and the smc cable modem. I changed the mac address by using it’s original and two cloned macs.

Still, i have the same ip address. I cannot get it to change.

Any thoughts?

Jim Warholic

A couple of thoughts come to mind on the Comcast Business class service. Either the DHCP server is not set up the same way at Comcast for assigning IP addresses, or maybe they actually have assigned a “static” or fixed IP address to your account.

If it is really a dynamic IP, then it is possible that the IP address is not based on the MAC address at the user’s end, and could simply be targeting the MAC address of the modem. Maybe they figure it more likely that in Business class setup, that the business customer would be adding a router and many other computers, and therefore business customers are less likely to maintain the same attached computer directly to the modem and Comcast doesn’t want the system to keep reassigning IP addresses for that reason.

Or, if you somehow got a static IP address that was assigned to you by Comcast, and you simply can not change it because it is fixed.


So what kind of things might I try?

I’m thinking Comcast is using the mac address of their comcast/smc “gateway” modem to set the ip. I have some access to the modem through the web admin panel, but the modem does not allow mac address changes/cloning.

I cleared my arp and then ran:
arp -a

before rebooting the smc modem I get xx.xx.xx.e4 (I thought I expected to see the cloned mac here and I do not)

I don’t know if I should be seeing something else, not sure what you see on your linksys (mine’s a wrt54g). I notice, fwiw, that under:
status -> router
my cloned mac address appears

status -> local network
sames as arp query result; xx.xx.xx.e4

status -> wireless
xx.xx.xx.e6 (same prefix as local network)

Can I try a different cable modem?

Jim Warholic

Ah, now it is making sense.

The Comcast modem and the router that you have are integrated together in one hardware unit, and is apparently lacking the ability to clone MAC addresses.

I believe you have the following Comcast modem/router SMC8014-BIZ. Download the manual from the SMC website. The SMC website search is located here.

If I understand your hardware setup properly, you are using another router on the output from the built in router of the Comcast modem/router unit. If that is indeed the setup, the separate Linksys router, WRT54G, is simply acting as another device on one of the output port lines on the Comcast modem/router unit. Because of this setup, you are not changing the MAC address at the source. You are only changing the MAC address of the Linksys router if you clone a MAC address on the Linksys router itself.

Now, for the solution to your dilemma and the answer to your question if you can try a different cable modem. I found a very very informative forum talking specifically about Comcast Business Class and more specifically about using a different modem other than the modem supplied by Comcast. Broadband Reports has a topic titled, [Business] Does Comcast Business still allow non-SMC modems? The forum article thread covers the topic extremely well from start to finish about adding a different modem to Comcast Business Class. Apparently, the simple answer is, yes you can install a different modem on Comcast Business Class. However, there is a bit more to the process than meets the eye. I suggest reading the forum thread carefully from start to finish.

By the way, here is a comment on the forum that supports the analysis presented here: “So long as your MAC address (attached to the modem, or the modem itself) doesn’t change, you’ll pretty much keep the same IP for quite a long time.”



I read that very article last night. It’s actually a bit confusing with the one poster reversing his position “it definitely will not work with dynamic, er I mean static”. LOL.

So then you and I agree it’s time to find a DOCSIS 3.0 capable cable modem, one where I can clone the mac.

I found a linksys cable modem on craigslist for $10, let’s see if this solves the issue 😉

Here’s an interesting post:

“Cable Modem manufacturers are utilizing practices that restrict your ability as a consumer to choose. ALL, I said ALL of the major manufacturers of DOCSIS 3 cable modems will only sell exclusively with multisystem system operators (MSO’s) aka your “cable company” and cut out consumers. So far I have found that NETGEAR, MOTOROLA, CISCO (Scientific-Atlanta) and SMC all have DOCSIS 3.0 cable modem equipment available, but are only selling exclusively to MSO’s. I know this because I’ve called all of them and asked them! Some of these companies have gotten angry and upset that I’ve asked them about this question.

These new modems have been out for some time (Cisco has had theirs out since at least March 2008) and you still cannot buy one.”

Oh, and thanks for the manual for the SMC. Yes that’s it. Main problem with it is it’s been modified and runs a ‘comcast’ web interface, not the “standard” web interface. The ip address of the modem is, in the manual they talk about using

The problem I’m having now is finding a docsis 3.0 cable modem. Think I can use a docsis 2.0? (They are easier to find).

Jim Warholic

I found some links on Amazon for DOCSIS 3 Cable Modems. Here is the Motorola SB6120 SURFboard DOCSIS 3.0 eXtreme Broadband Cable Modem and this for other DOCSIS 3.0 Cable Modems.

As far as compatibility questions as to DOCSIS 3.0 vs DOCSIS 2.0 it is important to note that the forum folks talk about the SURFboard SB6120 Cable Modem, though the article was written a while back. On the other hand, I imagine that Amazon has a number of reviews and comments that would be helpful to read over when trying to select your ultimate new modem.



So I just got off the phone with them. The problem is definitely that I have business class service and the modem/router (SMC8014WG) does not seem to allow for changes in the mac address. The solution is going to be dropping to residential service so I can provision my own router/modem. Apparently that’s not an option for business class people.

How strange.


Help! I followed your instructions but cannot change my IP address. I have a router that is hardwired to one computer and connects wirelessly to three others. I went into Linksys router and changed MAC address, then shut down my computer, turned off router, and turned off modem. Then I restarted everything, tried iprelease and renew, and my IP address is the same. Any help?? thanks!

Jim Warholic

You might try the recessed reset button on the cable modem. It is also possible that you had the computer’s MAC address in the Comcast system to begin with. I would try cloning another computer’s MAC address into your router such as a laptop and see what happens with the complete shut down, reset, and restart.


Did this once, appeared to work, got a different IP. A few minutes later no internet. Powered down the modem, waited, powered up. I’m back on my original IP.

I suppose I’ll have to call Comcast and ask politely for a new IP.


This is some very interesting information. It explains some (minor) problems I have had with comcast in the 12 years I have been with them. You do have to call them sometimes to get things ironed out — not an issue as long as you are not doing anything “shady.”

I’d just like to note that I have had the same comcast IP address for years at a time — the longest being about 3 years, with several 1 and 2 year stints. (I wanted this for remote control reasons.) You do this by hooking up the modem to a UPS. I even moved 10 miles and kept the same IP. I just kept the modem connected to the UPS in transit, connected it to the cable at the new house and everything worked fine. I was amazed because you’d think it would be a different node 10 miles away that would not allow an other node’s IP address. (I even went from 6 Mbps to 15 Mbps probably because it was a new development with new cable, repeaters, etc.) I think this shows the absolute key to getting a new IP is turning off the modem.

For example, the UPS died a few months ago (unbeknownst to me), and there was power outage for 5 minutes and boom! — a new IP address even with the same MAC address from the router. So just keep trying — in my experience anytime the modem is off for more than a minute or two (there is some “stickiness” for very short time periods), you get a new IP. So just keep experimenting and don’t rush and you should get a new IP address in short order. Good Luck!

Nilam Bhandalkar.

How do I change my IP address? I have been using a Reliance Netconnect modem, and i want to change my IP address when connecting with my laptop and PC but something is different. Please help me.

Jim Warholic

I suspect the Reliance Netconnect modems have similar ways of cloning a MAC address. Once you install the modem, I would see if you could log in to your modem using the typical IP address of ( ). Simply type that IP address into your local browser (Firefox, Internet Explorer, Crome, Safari) top address bar on the PC or laptop you are working on, and if that is the correct address for the modem, it will allow you to login with a user name and password. The default user name and passwords may be “admin” for both. Once you log in , then there probably is a “MAC Clone” button to allow you to clone the MAC address from a PC or laptop device.

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