bill142
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Mac Network Connection Problem

Mon Aug 04, 2008 11:12 am

I'm having issues connecting my iMac to my network. Everything worked fine this morning, and no settings have been changed. When I boot it into windows, everything works fine. I noticed some kind of application in the firewall called krb5kdc it looked some what suspicious. I'm at a total loss as to what's gone wrong. I'm running 10.5.4. Any help would be appreciated.
 
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moo
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 11:22 am

OS X does sometimes have a habit of losing your network connection information, I've had it happen to me. Just reenter it and all will be fine - until next time  Wink

Oh, and krb5kdc is perfectly OK - its a kerberos authentication daemon.
 
Klaus
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 11:43 am

Is your problem with the wireless network or regular cable ethernet?
 
bill142
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 11:46 am

it's the regular cable ethernet. I'm about to try connecting to my router wirelessly. The ethernet settings are currently DHCP and automatically assigning an IP of 169.254.92.254 which is nothing like the normal 192.168.1.2 that it usually has. When I try manually assigning one I get no response.
 
Klaus
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 12:08 pm



Quoting Bill142 (Reply 3):
it's the regular cable ethernet. I'm about to try connecting to my router wirelessly. The ethernet settings are currently DHCP and automatically assigning an IP of 169.254.92.254 which is nothing like the normal 192.168.1.2 that it usually has. When I try manually assigning one I get no response.

It looks as if your router's DHCP server feature isn't active or confused. Have you checked its setup? Have you checked it from another machine?

Power-cycling the router might help as well, even though it couldn't explain the problem.
 
bill142
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 12:13 pm



Quoting Klaus (Reply 4):
It looks as if your router's DHCP server feature isn't active or confused. Have you checked its setup? Have you checked it from another machine?

Well I'm connected to it right now using DHCP except I am in Windows not OS X. Everything in Windows is how it should be in OS X.
 
Klaus
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 12:41 pm

In the "Network" system preference, which network interfaces have you got?

Which ones are active (green)?

Is there more than one interface using Ethernet?

If there is only one of these, how is it set up?
If you can, you could post a snapshot of the settings, ideally plus a snapshot of the Advanced... settings, tab TCP/IP.
(To make a snapshot image of just one window, press [SHIFT][CMD]-4, then [SPACE] to get the camera cursor and then click on the window you want a snapshot of.)
Also interesting could be the output of the command ifconfig on the command line (Terminal).
 
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czbbflier
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 3:00 pm

Sorry for the slight digression....

Klaus! That "[SHIFT][CMD]-4, then [SPACE]" trick is absolutely brilliant!!!!!!!

I always wondered how to do that.

Back to our regularly programmed thread....

 
Klaus
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 3:32 pm



Quoting Czbbflier (Reply 7):
Klaus! That "[SHIFT][CMD]-4, then [SPACE]" trick is absolutely brilliant!!!!!!!

I always wondered how to do that.

It also works with menus, by the way.
 
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LTU932
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RE: Mac Network Connection Problem

Mon Aug 04, 2008 6:42 pm

Something similar happened on my Macbook this weekend, when running Vista through Bootcamp. Somehow, it wouldn't connect through the wireless, even though it said it was connected. I simply recycled the connection and everything worked fine again.

Additionally to the powercycling, I suggest you do the same in MacOS, recycle the connection (disconnect and connect again), just do that after the powercycling.
 
bill142
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RE: Mac Network Connection Problem

Tue Aug 05, 2008 7:59 am

I just changed all the settings back to how they were before they went awry, and then hit Renew DHCP Lease in TCP/IP, despite trying multiple times last night, and everything worked. Totally bizarre.
 
Klaus
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RE: Mac Network Connection Problem

Tue Aug 05, 2008 2:27 pm



Quoting Bill142 (Reply 10):
I just changed all the settings back to how they were before they went awry, and then hit Renew DHCP Lease in TCP/IP, despite trying multiple times last night, and everything worked. Totally bizarre.

Good to hear in any case...!  Smile

The exact settings you've had in the mean time might be of some forensic interest, but maybe it doesn't matter enough any more.
 
gkirk
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RE: Mac Network Connection Problem

Tue Aug 05, 2008 3:55 pm

Problems with a Mac? Well, I never  Wink
When you hear the noise of the Tartan Army Boys, we'll be coming down the road!
 
bill142
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RE: Mac Network Connection Problem

Thu Aug 07, 2008 8:49 am



Quoting Klaus (Reply 11):
The exact settings you've had in the mean time might be of some forensic interest, but maybe it doesn't matter enough any more.

It's happened again.

Here are the settings:



http://www.airliners.net/uf/536885560/phpG0kr4v.jpg
 
Klaus
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RE: Mac Network Connection Problem

Thu Aug 07, 2008 9:14 am

The net mask of 255.255.0.0 indicates a class B network. Home and office routers in most cases provide class C network spaces (255.255.255.0).

There's apparently a DHCP server active in the network at the same time which provides class B addresses.

I'd check all your computers and devices for enabled DHCP server functions first. Only the router should have it enabled (and probably configured for a class C network), all other devices should only have DHCP client functionality enabled. More than one DHCP server in the network is not good.

Theoretically under certain circumstances this might even come from outside; From your internet provider, for instance. But in such a case your router should have blocked DHCP broadcasts from the outside world.

To isolate the problem further you could also switch off IPv6 under "advanced", but as far as I know it should not have anything to do with DHCP in IPv4.
 
bill142
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RE: Mac Network Connection Problem

Thu Aug 07, 2008 10:36 am

Everything on the network has been disconnected and still no luck. I'm using my imac now, except using Windows XP and it's all working fine. I'm at a complete loss as to why nothing, not even configuring it manually in OS X, isn't working.
 
Klaus
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RE: Mac Network Connection Problem

Thu Aug 07, 2008 12:17 pm



Quoting Bill142 (Reply 15):
Everything on the network has been disconnected and still no luck.

Okay, so it's not a local device which provides the additional DHCP server. It would either have to be your own router or your ISP.

You could try to check which DHCP server provided the address. Copy the following command to the Terminal and execute it:

ipconfig getpacket en0

It should return various kinds of information about the DHCP lease and the server it came from.

You apparently have a rogue one in your network somehow (could be through your ISP), so finding out a bit more about it might be a start.

Quoting Bill142 (Reply 15):
I'm using my imac now, except using Windows XP and it's all working fine.

Which IP address does it use in that case?

Windows may react slightly differently to multiple DHCP hosts in the network so it may just accidentally ignore the second one while OS X doesn't.


Quoting Bill142 (Reply 15):
I'm at a complete loss as to why nothing, not even configuring it manually in OS X, isn't working.

What have you done manually, exactly?

You've got two main options there:

- "Using DHCP with manual address":
You can set a fixed address there, but name servers etc. will still be provided by the DHCP host. With a false DHCP server present, this can lead to name services being unavailable, though, so you could not access any servers by name. As long as the double server isn't sorted out, it's not an option, really.

- "Manually":
You'd set the fixed address manually (192.168.1.2 apparently), but you also have to set one or more name servers manually as well. You could temporarily borrow mine (194.25.2.129 — german T-Online) and enter it in the field DNS Server, but you're probably better off with one closer to home in the long run (such as the one provided by your ISP).
You will also have to set the Router field to the local IP address of your internet router (is it 192.168.1.1?).


You might also call your ISP to have them look into it — maybe the DHCP host info returned by the ipconfig command may help them to determine whether it's a problem on their side.

Multiple DHCP servers on the same network are bad and will almost always create confusion and problems, so it would be good to find and stop or block the additional one.

Your router might just be configured too generously, letting even DHCP packets through. It could be a good idea to check the NAT and firewall settings there. Normally there should be no exception rules active, but some malware is known to automatically reconfigure routers to make the connected networks vulnerable to attacks. Always have administrative access to the router protected by a good password and explicitly log out after making any changes to it.

Have you set any Proxy servers either on the Mac or on the router? That could be another source of problems.
 
bill142
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RE: Mac Network Connection Problem

Fri Aug 08, 2008 8:36 am



Quoting Klaus (Reply 16):

Ok I put in the DNS stuff and it connected fine. I switched it back to DHCP, and again, it worked, but we'll see how we go.

Thanks Klaus.
 
Klaus
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RE: Mac Network Connection Problem

Fri Aug 08, 2008 9:47 am



Quoting Bill142 (Reply 17):
Ok I put in the DNS stuff and it connected fine. I switched it back to DHCP, and again, it worked, but we'll see how we go.

Good to hear thus far.

But if the second DHCP server should still be present, the computer might just accidentally have connected to the proper one. I would in any case recommend that you check and secure your router... problems may still lurk in there.

Quoting Bill142 (Reply 17):
Thanks Klaus.

You're welcome.  Smile

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