Why is the IP on my Macbook (Network) different than my actual ISP

Discussion in 'MacBook Pro' started by mrogers, Apr 12, 2011.

  1. mrogers macrumors member

    Joined:
    Apr 11, 2011
    #1
    I have a dynamic IP address that should be changing regularly. However, I have noticed that whenever I check my Gmail logs (they show the most recent IP addresses to access the account) the IP address it shows there has been the same one for over 3 months now (ever since we set up the new Comcast Cable Modem and the Linksys router).

    Now I did an IP address check using one of the many websites that offer the service and it shows my IP address to be different than the one that shows up when I go to Network > Ethernet.

    it shows 3 different IP addresses for Ethernet, Subnet and Router, and neither of them are the IP address that shows up when I search it using the website. I even called Comcast to verify my IP address and their response matched with the website.

    So how come I have a completely differnet IP address showing up on my Network settings, and how come it has been unchanged since its installed?

    Is this an issue with my Macbook, my ISP or my router? Any idea whats causing this override?

    Thanks in advance!
     
  2. nyzwerewolf macrumors regular

    Joined:
    Jul 11, 2007
    Location:
    Long Island, NY
    #2
    hey bud,

    since you are connected to a Router, it gives you a "private" address.
    For example, if your ISP gives you an IP: 69.45.89.23, your router will give you a "private" ip of either 10.X.X.X or 192.168.X.X. Your router lets you connect multiple computers/devices to the network.
     
  3. nyzwerewolf macrumors regular

    Joined:
    Jul 11, 2007
    Location:
    Long Island, NY
    #3
    yes, it is true that the IP that Comcast gives you is a dynamic ip. If you plug in a different router or a pc directly to the modem, your ip will change. your router's mac address is binded to the IP on the ISP side. It is called DHCP reserve/binding.
     
  4. nyzwerewolf macrumors regular

    Joined:
    Jul 11, 2007
    Location:
    Long Island, NY
    #4
    This is not an issue. This is how a router works. :)
     
  5. mrogers, Apr 12, 2011
    Last edited by a moderator: Apr 12, 2011

    mrogers thread starter macrumors member

    Joined:
    Apr 11, 2011
    #5
    So the private router address never changes, correct?

    How then would one proceed to change their dynamic IP address. All the tutorials online show that you go to Network, Ethernet, then change it. However the IP address shown there is always the 192.168 Router IP, not the one from my ISP.

    How would I change that using my macbook?

    thanks again for answering and helping out a noob :) i appreciate it

    EDIT:

    For security purposes I don't like that my IP address remains unchanged for so long. I know there are some advanges to that, but none of which apply to me. So is there a way I can easily change my ISP IP address if ever needed?
     
  6. Bulldog321 macrumors newbie

    Joined:
    Jul 11, 2008
    #6
    Although ip addresses given by the cable companies are dynamic; don't be surprised if you have the same ip address for a year a more. It has been close to 2 years since my cable company has changed my ip address. The reason I know is that I haven't had to change my RDP or VPN logins for a long time.
     
  7. nyzwerewolf, Apr 12, 2011
    Last edited by a moderator: Apr 12, 2011

    nyzwerewolf macrumors regular

    Joined:
    Jul 11, 2007
    Location:
    Long Island, NY
    #7
    1) to change the ip address that comcast gives you, you have to power down your modem, disconnect your router from the modem, and connect a regular pc to your modem. this will change the IP that comcast gives you.

    2) you can change your "private" ip (192.168.X.X) given by your router, by manually entering in a new ip address that belong to the same network. for example, if your current ip is: 192.168.1.100, you can change it to 192.168.1.102. But it does not do any difference. Your private IP is not visible from outside.

    EDIT:

    If you connect your Linksys router back to the modem, it might acquire the previous IP address because the previous IP address is reserved for your mac address of your Linksys Router. This reservation hangs around in the DHCP Pool of the ISP's DHCP Server. This is called a "lease". ISPs have different lease periods on their IP-Mac Address reservation. It could be 15 mins or it could be 1 day. When that lease time expires because it cannot find the same device, that IP-Mac Address reservation is flushed.
     

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