IP changes a lot

Discussion in 'macOS' started by Kenny Pollock, May 21, 2006.

  1. Kenny Pollock macrumors regular

    Joined:
    Aug 26, 2003
    Location:
    Hollywood, FL
    #1
    I video chat a lot on my new MacBook using iChat. I have to forward the ports for iChat to this computer, but my 192.168.2.* number changes almost everytime I'm on my computer, it's the wierdest thing. I never turn the computer off, I just close the lid, open it when I want to use it... and the IP is constantly changing. It's setup with DHCP, should I set it up manually or is there a better solution? Thanks!
     
  2. Queso macrumors G4

    Joined:
    Mar 4, 2006
    #2
    Do you have admin rights to whatever is throwing out the DHCP addresses? If so, you can lock down the IP address to the interface itself, so that you always get the same address when on that network.

    Each interface has a 12 digit address in Hexadecimal. To get it for your MacBook, open the Terminal (it's in the Applications/Utilities folder) and type

    ifconfig en0 <-- if you're using the Ethernet port

    or

    ifconfig en1 <-- if you're using the Airport Extreme port

    In the output you'll get a line like the following

    ether 00:14:51:25:2d:6e

    That's the interface, or MAC, address. Look on the DHCP server and set up a "DHCP reservation" to link the interface to the IP address you always want it to receive. It should be obvious where you put the MAC number.

    Note that your DHCP server may be integrated into your router. Check the manufacturer's documentation for a how-to.
     
  3. Kenny Pollock thread starter macrumors regular

    Joined:
    Aug 26, 2003
    Location:
    Hollywood, FL
    #3
    Thanks, sounds like exactly what I need but... I can't find any setting that will allow me to do this on my Linksys router administration screen. Would you happen to know how to on my router (or if it can be done)? I did a quick Google and found that Linksys routers didn't have this feature, but I don't trust EVERYTHING I read.
     
  4. Queso macrumors G4

    Joined:
    Mar 4, 2006
    #4
    What model router is it? There may be a firmware update that adds it in.
     
  5. Kenny Pollock thread starter macrumors regular

    Joined:
    Aug 26, 2003
    Location:
    Hollywood, FL
    #5
    Model BEFSR41, running firmware version: 4.04.01
     
  6. Queso macrumors G4

    Joined:
    Mar 4, 2006
    #6
    Looks like you're right about it not supporting the feature. That leaves you with no option but to use Static IP addressing.

    Assuming that the router uses the IP address, 192.168.2.1 you should configure System Prefs>>Network>>interface>>TCP/IP on your Mac as:-

    IP Address - 192.168.2.2
    Subnet Mask - 255.255.255.0
    Router - 192.168.2.1

    DNS Server - 192.168.2.1 <- unless there is already something in this box. If there is leave it alone.

    Once this is done, check that you can still get both on the router and the Internet. Then set the port forwarding to 192.168.2.2 for only the service(s) you need.

    NOTE: If this doesn't work, switch the Mac back to automatic addressing.
     
  7. trainguy77 macrumors 68040

    Joined:
    Nov 13, 2003
    #7
    You should set the IP to something like 200 so it does not get duplicated, some DHCP servers will still hand that IP out then you will have all sorts of problems, however high numbers should be handed out alot later on. Unless you have some custom setup.(which I don't think you do):rolleyes:
     
  8. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #8
    If it's not too RTFM... can anyone explain how to do this (lock a MAC address to an IP address) on an AEBS?
     
  9. trainguy77 macrumors 68040

    Joined:
    Nov 13, 2003
    #9
    I took a look around on mine and I don't think you can. I have done it on true DHCP servers. However it does not seem to be in AEBS. Most home routers don't have this feature.
     
  10. mkrishnan Moderator emeritus

    mkrishnan

    Joined:
    Jan 9, 2004
    Location:
    Grand Rapids, MI, USA
    #10
    Okay, this was the conclusion I drew, too, but I wasn't sure. I know that you can try and do it from the client side, which is what I've done when I wanted my iMac in my DMZ.... It would be nice to have all my standard devices locked down to fixed localnet IP addresses, though.... I was hoping that the Airport Extreme Base Station was a little bit more than a standard home router and could handle this, but I guess not.
     
  11. trainguy77 macrumors 68040

    Joined:
    Nov 13, 2003
    #11
    Now if you wanted a real firewall you could always set up a m0n0wall http://www.m0n0.ch/wall/ but that might be to much for you. It will run on almost any PC. A 233 mhz works great! (off topic)
     
  12. auyongtc macrumors member

    Joined:
    Apr 23, 2006
    #12
    Simple workaround to this "lack of features" on home routers:

    - Check the DHCP function on your router, to see how many IPs and starting IP address it will automatically issue out to connected clients. If it starts with x.x.x.100 and issues up to 50, the range is until x.x.x.149 then.

    - If that's the case, u have from x.x.x.150 till x.x.x.254 to mess around with (assuming it's a Class C subnet that it's set to - typically 192.168.0.x or 192.168.1.x - then again, I've seen some routers default to 10.x.x.x Class A)

    - With that, you can safely use say from .150 till .254 to manually assign to your computers/devices that need port mapping. Assign them in this manner:
    IP Address: x.x.x.150
    Netmask: 255.255.255.0 (typically)
    Gateway: (router's IP - probably x.x.x.1)
    DNS Server: (router's IP - probably x.x.x.1)

    - Then for the computers/devices that you have manually assigned its IP, you can now add port forwarding to your heart's content.

    - Anyway, as an example, most Linksys routers have a DHCP feature that works for range 192.168.1.100 - 192.168.1.150 (if it's listed as 50 addresses). It's router IP is typically 192.168.1.1, so when assigning your computers as a manual static entry, setup the addressing on the computer as:
    IP Address: 192.168.1.150
    Netmask: 255.255.255.0
    Gateway: 192.168.1.1
    DNS Server: 192.168.1.1

    - For the next computer, use IP of 192.168.1.151 instead, while the other settings remain the same.

    Hope that helps :)
     
  13. Kenny Pollock thread starter macrumors regular

    Joined:
    Aug 26, 2003
    Location:
    Hollywood, FL
    #13
    Thanks for the help, manually doing it worked great, and a couple restarts have kept the IP the same and no other computers on my network are interfering yet.
     

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