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Past few days my internet has been automatically getting a Self-Assigned IP on en0. I heard it does this when it can't retrieve a DHCP Server from the ISP.

I've tried these solutions below.

  1. Deleted com.apple.alf.plist
  2. Deleted NetworkInterface.plist
  3. Reset Ethernet Configurations

When I connect to my ISP to get the Router, Subnet and IP settings does it take the system's Mac Address? because changing the last digits of my Mac Address always did the trick but not anymore.

I connected the same Ethernet wire to another MacBook and it connected successfully.

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Do you have control of the router or any information that can be added? Normally the DHCP is set on a router and it is set up to respond to anyone that connects. Might this be a corporate network where security is preventing unknown devices from connecting? –  bmike Jan 31 '13 at 16:12
    
I don't have access. Unknown devices? Why is it an unknown device all the sudden when it was connecting for months? I think it has to do something with Mac Address. What do you say? –  Dylan Cole Jan 31 '13 at 18:08

1 Answer 1

This looks like a basic networking issue where you might need some knowledge to sniff the packets on en0 using tcpdump.

The things that are known to prevent DHCP from reaching the OS are:

  1. Firewalls (OS X, Little Snitch type, malware, and/or internet firewall like Symantec and others)
  2. Network setup where the DHCP server only sends addresses to machines that are cleared for the network

You seem to have done some of the easy troubleshooting, and I personally don't ever like deleting some plist but not all plist since there are many keychains, system plist, ByHost plist and others so you could actually make a problem partially deleting information on networking.

The one thing I would do is re-connect the known machine and record the IP address that gets assigned and swap in the "suspect" machine and force the IP to be the same. If you get network connectivity then you are on the right track with DHCP issues.

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I copied the settings from a working macbook to this and It says it's connected but it's not giving me any ping to any sites. I then chose Ethernet settings to "Using DHCP" for odd reason It actually got the DHCP automatically and connected normally! Why is it acting so random? I have a feeling that this problem is going to occur again. –  Dylan Cole Jan 31 '13 at 18:07
    
The problem started again. –  Dylan Cole Jan 31 '13 at 21:02

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