03-26-2011, 09:56 AM

Coming to you from my iPhone since my iMac is giving me problems.

Basically, my iMac computer is having trouble getting an address for my dhcp settings for our wireless network. I went in two days ago and tried to manually reset the data when this started. Now, it appears that if I can find the proper number that I can get the computer back online.

My problem is since I went in and reset manually that I cannot get the dhcp to work automatically. It keeps trying to go back to manual settings when I renew dhcp lease.

Previously, I had settings of

IPv4 address 192.168.2.4

Subnet Mask 255.255.255.0

Router 192.168.2.1

Now when I try to reset my numbers back to

IPv4 address 192.168.2.4

I get a message of

IP Configuration

192.168.2.4 in use by 00:24:36:43:97:a2

........basically, I need some help in finding the 'next' or 'new' correct number for the dhcp settings, or at the very least a way to restore that last number back to 4.

And yes, my previous problem from February was fixed but I never fuy understood how or why, it just seemed to fix itself somehow. I don't know egg my other post on this subject I made a day or so ago seems to have disappeared.

03-26-2011, 10:00 AM

Ok, weird.....my iPhone now seems to have the 192.168.2.4 address. So how or what do I put for my iMac? I could have sworn just a day or two ago that my iPhone had the 192.168.2.3 address.

03-26-2011, 10:03 AM

DHCP issues are a rarity on a small network (well, to be honest, on a properly configured large network, they are a rarity as well). Most of the time when I see these things on a small wireless network, it usually indicates an issue with the security settings on the wireless router.

What kind of security do you use on your wireless network? If you plug your Mac into a network port on your router physically, does the problem go away?

03-26-2011, 10:09 AM

The IP addresses are assigned to your local devices by the DHCP server in your router. These numbers can change as different devices connect and disconnect from the router.

Unless there is some specific reason you need a specific device to have the same IP address all the time, there is no reason to be concerned about what it's IP happens to be.

Do not use the manual option to set your IP on your Mac from within Network Preferences - won't work - head for the TCP/IP tab and hit the Renew DHCP lease button. What do you mean it goes back to manual settings - that button will set your IP with whatever the router currently assigns to that machine.

(The type of security you're using can play a part also - and cwa is better with this stuff than I am - I should know better than to answer these while he's online - )

03-26-2011, 10:58 AM

What I mean is that when I go into the network settings at the moment and bring up TCP/IP, that the Configure IPv4 is selected as manually.

When I choose the window using the mouse, and try to move that into the Using DHCP setting

(as compared to
Using DHCP
Using DHCP with manual address
Using BootP
Manually)

....that when I choose Using DHCP and click the Renew DHCP Lease option, that my chosen selection goes back to Manually rather than staying with the Using DHCP setting.

This is preventing me from the Using DHCP option.
I am unsure of router settings; our wifi network at this residence is passworded (secure) and our router has the *.*.*.1 address as I listed.

It's maddening because inknoe all I have to do is get my imac to read the correct DHCP setting numerically and I can be back online with it again. I just don't know the way to do that at the moment. So this comes to you from my iPhone.

Also how did my iPhone suddenly get the DHCO setting my iMac had? I've tried to give the iMac the setting my iPhone had but the 192.168.2.3 option doesn't work.

03-26-2011, 11:17 AM

*sighs*

Ok I'm on the iMac again but posting real quick from iPhone.
Here's what I did:

-Configure IPv6 kept coming on selected as automatically.
--I went in, chose Off and selected Okay.
---then clicked Apply at the main network window which showed my Airport status network connection among other items

- then I went back into TCP/IP settings and chose the DHCP setting
--this reset my DHCP for my imac

03-26-2011, 11:17 AM

Originally Posted by AlexanderC

What I mean is that when I go into the network settings at the moment and bring up TCP/IP, that the Configure IPv4 is selected as manually.

When I choose the window using the mouse, and try to move that into the Using DHCP setting

(as compared to
Using DHCP
Using DHCP with manual address
Using BootP
Manually)

....that when I choose Using DHCP and click the Renew DHCP Lease option, that my chosen selection goes back to Manually rather than staying with the Using DHCP setting.

This is probably because it can't get DHCP because it can't authenticate to the network. Probably the easiest thing to do is click the Airport connection in the left window pane and then click the '-' to delete it. Then re-add the Airport adapter and it should be back to factory defaults. Attempt to reconnect to the wireless network as if it were a new machine and it should be OK, assuming that you don't have a security issue.

This is preventing me from the Using DHCP option.
I am unsure of router settings; our wifi network at this residence is passworded (secure) and our router has the *.*.*.1 address as I listed.

Not necessarily secure just because it's using a password. It could be using WEP, WPA or WPA2 (with the latter two choices being the correct ones, preferably WPA2). You need to hard wire to the router, get into its configuration and verify this before you go any further. If it's using WEP, you're making this harder than it has to be and for absolutely no security benefit, since breaking WEP is child's play.

It's maddening because inknoe all I have to do is get my imac to read the correct DHCP setting numerically and I can be back online with it again. I just don't know the way to do that at the moment. So this comes to you from my iPhone.

Also how did my iPhone suddenly get the DHCO setting my iMac had? I've tried to give the iMac the setting my iPhone had but the 192.168.2.3 option doesn't work.

I don't think you quite understand what DHCP is. Every computer on a network needs an IP address. In the old days, you would manually set your IP, provided by your ISP. About 16 years ago (or so), DHCP was introduced as a way to automate this process (which was incredibly cumbersome). Basically your router has a pool of addresses (254 of them, to be exact) that it can hand out as devices connect to it. Each time a device connects (and authenticates properly - i.e. the password is entered correctly and the router agrees that it should be allowed to connect), it hands the device an IP address from that pool.

Typically the device will always get the same address, but it can (and often does) vary. So, your iPhone may be getting .3 because as far as the router is concerned, the Mac isn't connected and it's an available address to hand out.

The trick to solving this problem is getting your router properly sorted - and just based on my observations here, you're getting hung up on the authentication piece - probably because you're using WEP encryption for security. So, please don't underestimate the importance of getting that straightened out - not only for the sake of configuration, but for ease of use, security and performance - you need to be using WPA at a minimum.

03-26-2011, 11:25 AM

Originally Posted by AlexanderC

*sighs*

Ok I'm on the iMac again but posting real quick from iPhone.
Here's what I did:

-Configure IPv6 kept coming on selected as automatically.
--I went in, chose Off and selected Okay.
---then clicked Apply at the main network window which showed my Airport status network connection among other items

- then I went back into TCP/IP settings and chose the DHCP setting
--this reset my DHCP for my imac

Interesting. I would still strongly encourage you to check on your wireless security settings. This should be entirely seamless - and just based on what you're describing that router and your Mac aren't playing nice. That almost always points to a configuration problem, which in most cases is WEP-related.

03-30-2011, 02:23 AM

Originally Posted by cwa107

Interesting. I would still strongly encourage you to check on your wireless security settings. This should be entirely seamless - and just based on what you're describing that router and your Mac aren't playing nice. That almost always points to a configuration problem, which in most cases is WEP-related.

The OP has posted several times on the subject and I've posted many many support posts. The problem is so clearly the router but the OP seems to be exceptionally reluctant to resolve the router issues, which were 'fixed' but are now back and keeps re-posting the 'iMac issue'.

I'd still like to try and help the OP resolve the issue but without getting into the router config and eliminating the local interference on the same wifi channel (the route of the intimitant nature of the fault I believe) I think the problem will keep returning.

http://www.mac-forums.com/forums/air...ml#post1206940

Need some assistance

HELP! iMac won't let me renew DCHP setting!

What does this mean?