LAN IP changes

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Level 1

12 points

LAN IP changes

I posted at any forum yesterday but have got no reply. Here may be a better place.

My iMac is connected to a Netgear router. In the router set-up, I specified two IP address for this iMac, one for wired and one for wireless. The problem is, although I reserved an IP for the wireless connection, the IP that is actually used by the iMac box changes in various sessions. In the router setup, I specified 192.168.1.3 for the wireless card. It was fine right upon the setup. However, after I woke it up from sleep, it would change to 192.168.1.5 (as 192.168.1.4 is reserved for the wired card). But after one or two sessions, it would change back to 192.168.1.3.

I didn't have this problem previously when I was using any iMac running Tiger.

Is this a problem with Leopard? Or one with Netgear+Leopard?

This creates problems with the port forwarding setting.

Any help please?

iMac, Mac OS X (10.5.1)

Posted on Dec 13, 2007 9:04 AM

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Answer 1

Dec 13, 2007 9:15 AM in response to KenWong

One thing you can do is in the "Advanced" options in the "network" system preferences, under the "TCP/IP" tab you can force the computer to use a certain IP address instead of getting it dynamically. In the "Configure IPv4" menu select "Using DHCP with manual address", and then enter the address you've forwarded ports to in the router. The address reservation usually depends on your MAC address, and problems with that could be with your router. Perhaps a firmware upgrade would help, or some other sort of reset. However, using a manual address should be a solid workaround.

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Answer 2

KenWong Author

Level 1

12 points

Dec 13, 2007 9:26 AM in response to Topher Kessler

Hi Topher,

Thanks for your prompt help. I have done what you told me to. It takes time to see the results. Just woke it up from sleep to make the change, it used the 192.168.1.3 IP address again. Seems that it switch between 192.168.1.3 and 192.168.1.5. Can't understand really. My guess is, when the box goes to sleep, the address it was using cannot be released immediately. So, when I wakes the machine up, it has to use another address.

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Answer 3

Dec 13, 2007 9:30 AM in response to KenWong

If you've assigned the IP address manually it should not change at all, and the IP address change should be immediate. Entering the IP manually should lock it in so the computer uses no other except that one. Are you sure that in your computer in the network system preferences you're entering the IP address in the "TCP/IP" advanced options? If you're not specifically entering the numbers yourself then you're letting the computer get them from the router.

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Answer 4

Felix T

Level 1

76 points

Dec 13, 2007 12:53 PM in response to KenWong

Are you connected both with a cable and wirelessly? Are you changing from a wired connection to a wireless connection and back?

I would avoid using MAC reservation on the router and instead use the "DHCP with manual address" setting in the TCP/IP window of the Airport pref pane and in the Ethernet config. Use the same address for both.

Felix

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Answer 5

KenWong Author

Level 1

12 points

Dec 14, 2007 7:10 AM in response to Topher Kessler

Hi Topher, sorry that I didn't make it clear.

I said it seemed switching between two (or three) LAN IPs. That's the situation I observed before I change the settings in System Preferences as you told me to.

After I made the changes in System Preferences, I tried it out once. I put the box in sleep and woke it up in 2 or 3 minutes. It kept the IP, i.e., 192.168.1.3.

However, it failed again in a few hours but in a different way.

This morning, I myself woke up and then woke the iMac up. It couldn't connect to internet, and even the router setup via browser.

I had to change it back to "Using DHCP".

Message was edited by: KenWong

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