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How can I use two ip addresses from one cable modem?

I have a high speed internet via a cable modem. I received 2 ip
addresses from my provider. Can I use 2 different routers: Linksys and
Watchguard Firefox Soho, and still have dhcp enabled on both?

Well, you certainly can, but in most cases it only makes things more
complicated than they need to be.

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To actually do it, I’d put a hub in front of the two routers. So your cable
modem would go into the hub, each router would be connected to the hub, and
each would configured to respond to one of your two static IPs. You could then
connect your computers to one router or the other, as you saw fit.

I’m just not sure why, in most cases, you’d want to do so.

The drawback here is that your machines on one router will not be able to
share folders or printers with machines on the other router. Each router
represents its own private sub-network on the internet.

Multiple internet IP addresses are really only useful if you have multiple
computers that you want to access from the internet. For example you might want
to set up two web servers, in which case each would need its own IP address.
For most common home and small business situations, that kind of setup is
actually pretty rare.

My ISP has allocated me 5 IP addresses here at home, but I use only one. All
the computers in my house (8, I think) are connected behind a single router. I
really don’t have any need for the other 4 IP addresses at this time.

I suspect that, unless you’re doing something special, you really only need
one of your two IP addresses. It’ll certainly be the simplest approach.

Do this

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32 comments on “How can I use two ip addresses from one cable modem?”

  1. Some cable ISPs configure your cable modem with only 1 IP address by default and charge a few dollars a month for extra addresses. If your ISP only provides you 1 address, a router would be required to share that address between your computers.

  2. A special case where you might WANT something like described in the article;

    – you have a home network behind one router (using your first IP address)
    – you have a server with your second IP address

    So now, your server is now ‘isolated’ from your home network; which should make your home network more secure (since potential hackers won’t be able to get to your ‘home network’ THROUGH your now isolated sever)

    Another case might be if you want to seperate two groups of people (so that each group is ‘isolated’ from each other) ie. So Group A can’t get onto Group B’s network and visa versa.

  3. Hello,
    I am trying to set-up 2 ips in my house. My provider gives me 3 ip addresses, which right now I am only using one of course. My question is do I need a separate router (2) for each ip address? Right now I have a wireless route that connects two computers, xbox, 3 playstations. But I need to take advantage of at least one more of the ip addresses for a different computer (this computer is for a room-mate which needs a different ip address). So do I follow the same directions above by getting another router and hub?

    Thanks, Amy

  4. Hi,
    I need to do this, but im using two dynamic ip addresses, I was woundering if insted of using a hub, could you use a switch. I have a switch I am not useing. I want this to seperate my one xbox from the other because I get network errors with them on the same network. Thanks for any help!

  5. I have a high-speed line coming in to my home with DHCP for my initial wireless router (D-Link). DHCP is running on that router. Behind that, I would like to place another wireless router that would serve a separate section of the house (Netgear). I purchased a second router because it was cheaper than an access point. Did I make the wrong decision?

  6. I own a duplex, both myself and my tenant are running able modems… other than purchasing a router with two WAN ports to do load balancing, is there a way to amalgate the connections to double my theoretical speed? For instance, and I could probably just spend an afternoon testing this, could I take oen of my spare switches, run both cable modems into it, and channel that into the WAN port of a single router, from there hit another switch, and allow our networks to merge? I can VLAN if I feel the need for security, but I really don’t… During the week I use a lot of bandwidth on media applications while they use very little for email and the like… While I’m gone on weekend hikes they play WoW and other online games, so sharing the bandwidth would work out well…

  7. Can this also be done with a dsl modem? I know that with a dsl line you usually use PPoE to connect. Our dsl provider has given us 6 ip public ip addresses to use and due to having several servers running we would like to issue each of them a public ip.

  8. The reason why someone would want to do this is to get 2 xbox’s on xbox live at the same time in the same household.

    Since there doesn’t appear to be a way to get two of them to sign in at the same time on the same connection due to port issues.

  9. Hello I have problem with my ISP I need Band Width 512kbps Static IP but he cant provide me. they can give me Band Width upto 64kbps Eight different Static IPs. I wanted to know is there any Software or Device from which i can get help to make by my self a Static IP of 512kbps. Please answer me in detail so i can understand

  10. Leo, I just read your comments on ‘How can I use two ip addresses from one cable modem?’ and I have a question. First the problem: two divisions in our company who were completely independent, seperate physical locations, domain controller, webservers… (except for VPN), are moving into our new building together. The long term goal is to have one domain and one network, but my short term goal is to get people back to work. I need to maintane two domain controllers each on a seperate subnet behind one cable modem with 5 static ip address assigned to it. Your solution of a hub sounds easy enough. Is that the best way to share the internet connection for now or is there a better way?
    Thanks a lot for your advice.

  11. Leo,

    I have client software for car washes that require that I use multiple IP addresses, how do I setup my router to use a single cable modem with two separate IP addresses?

    I’m using a netgear FVS318.

    I alos have 2 connections for credit card processing, 1 for a computer, and 1 for my CCTV system.

    Please help, COX is not help, and the company who makes my car wash equipment doesn’t know how to port forward, so this is way beyond them!



  12. i have a DSL connection and the ISP gave us 7IPs so how can i possibly use all of those IPs and i’m using D-Link router..

    please help with these

  13. Hi,

    I have one broadband line into my property, yet my ISP has allocated 5 IP’s.

    I want to set up SBS 2008 in a test environment to get to grips with it before rolling it out to a client. To test exchange i need use 2 external IP’s but i only have one connection, and my router has only one WAN port.

    Is it possible to configure a draytek 2600G to use 2 external IP’s through one phyical connection?

    There are various options such as WAN alias addresses, but i am unsure how to link the external IP’s to the correct machine? Do i create VLAN’s and set port forwarding?

    Any help would be greatly recieved!!

  14. My cable provider does not supply static IP addresses. Can this still be done without static IP’s? If so how does each router know to get a different IP address?

  15. Hi, Leo
    Can u help me with that, i have one router and 2 computers. they both are same ip-s. but i play one game with my brother and i was wondering, if there is possible to change ip-s to different? then we could have different ip-s with one router. can u help please. thanks

  16. hello i need second 2 ip address beacuse i have ojo and viedo phone now they spreated easy to contact which can easy to contact ????

  17. i have a laptop that is connected to peoplepcdsl daughter who is in the same apartment as i am has a verizon dsl can we use our computers at the same time when i only have i phoneline

    You can’t – at least not the way you think. The DSL on your phone line is connected to only one, PeoplePC or Verizon, regardless of which modem you use.

    – Leo
  18. Hey. I have a couple of questions.
    Like let’s say, I’m currently playing Xbox Live, and I have 1 cable modem and I’m using 1 wireless router.
    When my family uses the computer I start lagging on Live. If I buy a second router, would it stop this problem?

    Unlikely. You’re more likely limited by the speed of the internet connection to your home.


  19. I have 2 networks setup and 2 IP addresses. I use one network for general home stuff and my wireless IP cameras are on the other. This way, I don’t eat up the bandwidth of my home network. I access my cameras through my dyndns domain via port forwarding on my camera network. So far this has worked for me very well. This is the only reason I would do this since it is a specialized use.


  21. Took me 2 days to figure out, thought I’d post it for others the easiest way to get two playstation’s running simultaneously on a home network is to use a Switch and make sure your ISP provides you with 2 IP addresses. You’ll NEED 3 IP addresses if you plan to use any other computers on the network. Use the router to separate the rest of the network from the two ps3. Use wired connections for the PS3.

    –1 PS3
    –2 PS3

    This setup will guarantee your able to join parties together in seconds(no waiting time or party kicks)

    You shouldn’t ever be kicked out of game by connection errors. (typical problem with this game)

    Which means you won’t get penalized for the game’s inability to support all routers properly.

    (why don’t games collaborate with a router company, like a certified PS3 Router)

    Uncharted unlike most other games has serious problems finding players, joining parties, or disconnecting from games, after testing, configuring many routers, opening ports, static ips, dmz, firewalls, routing ips, qos engine priorities, etc. your just wasting your time! If your not experiencing problems, great! ignore this, but if you are, don’t waste your time!, get the setup i mentioned above and you will be set gaming for 10 hours straight together with your brother or sister watching others get disconnected .

    Spread the word! this is specifically for Uncharted 2, connect directly and you won’t have a problem anymore. Hopefully Uncharted 3 will have fixed these network issues. Enjoy!


  22. I have 2 PC’s and 2 IP addresses,each pc recognizes 1 IP address. I have it connected internet cable to modem,from modem to a linksys 5 port switch and from there a network cable to each pc works great. I did this because when I had 1 IP address and used a router my buddy and I would go to same online game play for a while but then get kicked, not sure if server saw us as one in the same. Anyway someone said if I got 2nd IP address and connected as above game server wouldn’t kick us and it never has since. Each pc always has the same IP address they never switch back and forth.How does each pc recognize same IP address everytime you boot them ?

  23. You should change the title of this article to something like “Should I use two IP addresses from one cable modem.”

    This is the antithesis of a how-to article. Instead of explaining how to do it, it argues against doing it at all. I’m wonder if you even know the answer to the question in the first place.

  24. @ Brian
    “This is the antithesis of a how-to article.”
    Much of Leo’s advice seems to be pitched at the home user rather than the corporate sector/pure technical advice sector.
    That advice appears to try to determine what the home user/writer is trying to achieve and he gives advice that he feels would be more appropriate to their needs.
    Many replies appear to be not strictly from the “workshop manual “


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