Self-assigned IP !!! Can't connect via Ethernet

Hi all,

This is my problem:
- Now every time I connect my MBP (using 10.6.4) to my hall's network (staying on campus, in uni) it appears as "Self-assigned IP" and cannot connect to the internet for the Ethernet. It suddenly happened a few days ago and I have no clue what caused that
- Airport's working well
- Using Windows on Parallels and can still connect to the Internet despite that the Mac OS X does not at the same time, my friends' laptops have no problems as well
- Tried taking the IP, subnet mask, router( I suppose in Windows it is called Gateway ) details and typing in manually for the Ethernet settings on OSX but still cannot connect to the Internet. The status is Connected and "Ethernet is currently active and has the IP address 137.xxx.xx.xx."
- When I bring my laptop to a different place and connect via Ethernet, it works well, too, I just leave the setting to be "Using DHCP"



I've seen that lots of people have met this issue, also loads of advices have been given:
- reset the router ... --> I'm connecting to the hall's network, so that's impossible for me to do
- sudo ipfw list , sudo ipfw flush .. --> nothing changed afterwards
- someone suggested uninstalling any VMware --> tried uninstalling parallels desktop and the problem's still there
- untick the "Use Passive FTP Mode" for ethernet --> no difference
- Security settings ,Firewall --> firewall was even off when the issue 1st appeared



So ANY SUGGESTIONS PLEAAASSSSSSSSSEE !!!! I'm sick of having to turn to Windows just to access the internet
Thanks in advance

Queso said:

This can happen when the DHCP server takes too long to respond. OSX doesn't wait as long as Windows and Linux for a DHCP address offer. Easy way to test is to go into your networking settings, and click on the Renew DHCP address button multiple times in quick succession.

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That's the 1st thing I tried didn't work

@cwaddell2002 : how can they block just my MAC ??
will complete installation of MAC OS fix the problems ??

Queso said:

The MAC address is burned into the Ethernet controller, so it won't matter what Host OS you're running on the Mac it will always be the same.

Have you contacted the network admins at the college? They will be able to tell you whether the DHCPREQUEST packet your MBP sends is being received by a DHCP server.

I'm wondering whether the problem is that Parallels was using a different MAC address at the moment the network admins have activated a port security or ARP spoofing protection, meaning that the port you are connecting the MBP to is now linked to the MAC the Parallels installation is using. These sort of setups are quite common as it prevents users extending the network with hubs, but can cause issues where virtualisation software is installed. Once again, the college's network admins are the ones to talk to.

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I think what I need to do now is contacting the college's network admins :-? thanks

Do you have any sort of web proxy on?

By connecting to the internet I assume you mean "open a web browser and browse the web", since other programs that use the network (Parallels) still work.

Click menu > System Preferences > Network preference pane, then click Advanced button and Proxies tab to check.

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no web proxy has been on , and I didn't just browse the web, other programs running on Mac can't connect to the Internet,either, such as : Itunes, mail, adium... and from the liitle snitch's network monitor, I can see that there's no response from the network