Wireless and LAN on same IP ?

Question

Wireless and LAN on same IP ?

Hi

We have a lot of wireless users who keep forgetting to plug laptops back into LAN and so their assigned IP is DHCP-based in range x.x.x.1-50.

This is annoying because the machine keeps moving around in ARD lists.

We use a Microsoft 2003 Server for DHCP allocations and I thought of assigning a reserved address to each machine, but using same IP for wireless and LAN. As the wireless is always on will this cause problems if they plug in the LAN cable?

Seems to me that they'd be a clash, but unless you're using port teaming the Mac is using either wireless or lan not both, surely?

Interested to hear what people think and if anyone's tried it.

Cheers
C

MacBook Pro 15" 2.16GHz Intel Core 2 Duo, Mac OS X (10.6.1), Second display is Apple 24" LED, but it is being repaired at the moment.

Posted on Nov 5, 2009 9:12 AM

Reply

Answer 1

Kappy

Level 10

361,837 points

Nov 5, 2009 10:11 AM in response to Craig Roberts1

You can have both wired and wireless connections at the same time. The router assigns a different local IP address to each network connection whether it be wired, wireless, or both. Because the router is performing NAT there is only one IP from the ISP which is the "real" IP address. This IP address is always the same unless your ISP changes it when the DHCP lease is renewed or if you have a static IP address assigned by your ISP.

Although you can assign each machine a static IP address within the local block you cannot assign the same IP address to more than one machine or more than one network connection. This is the reason for using DHCP because then it's not necessary to keep track of the assigned IP addresses. That is handled by the DHCP server within the router.

The main problem with port forwarding is the need to specify the machine address. If the user's computer is disconnected and reconnected frequently, then that local IP address will likely change. Then you may need to pick a static IP to use for that particular user's machine. It must be an IP within the router's DHCP block but cannot be one already in use. That user's Network preferences should be configured to use DHCP with manual addressing.

Reply

Answer 2

micp

Level 3

650 points

Nov 5, 2009 10:23 AM in response to Craig Roberts1

You have a case for using DHCP reserved addresses for wireless, it will just give you the administrative overhead of tracking an extra ip per ARD user.

Feel free to correct me if I am wrong, but I don't think it is allowed to reserve one ip for more than one MAC address. One MAC for ethernet and one MAC for wifi, and a seperate ip for each.

Even though you are correct and the Mac will only use either the wired or the wireless depending on preference settings I don't think you will be allowed to do this on your server.If your server allows you to set yourself up for potential duplicate mac address conflicts and issues I would be surprised.

Reply

Answer 3

Strolls

Level 1

58 points

Nov 5, 2009 12:08 PM in response to Craig Roberts1

Craig Roberts1 wrote:
...
We use a Microsoft 2003 Server for DHCP allocations and I thought of assigning a reserved address to each machine, but using same IP for wireless and LAN. As the wireless is always on will this cause problems if they plug in the LAN cable?

Yes, it will.

Can't you address the machine by DNS name in ARD?

In this case you should be able to assign different fixed IPs to each machine in DHCP (eg: 192.168.1.101 to LAN, 192.168.1.201 to WLAN) and then both can be addressed by the same name in DNS (or at least in reverse lookup, which would hopefully keep your ARD lists neat).

If it's wasting a lot of time trying to find the right machine, and you keep logging into the wrong one by mistake, I can see why you'd want to do this. If it's just a matter of neatness in the ARD interface then I think this could be more trouble than it's worth.

Stroller.

Reply