Failure to acquire IP over DHCP
Marko Vojinovic
vvmarko at gmail.com
Thu Aug 30 16:24:58 UTC 2012
On Thursday, 30. August 2012. 17.01.36 Suvayu Ali wrote:
> On Thu, Aug 30, 2012 at 10:43:59AM -0400, Mark Haney wrote:
> > On 08/30/2012 10:36 AM, Suvayu Ali wrote:
> > >I have a weird problem; at my office every time I try to connect to my
> > >wall outlet, my laptop gets assigned an internal IP (192.168.0.114) and
> > >I cannot access the internet. However everything works as expected when
> > >I use any other wall outlets.
Let me guess --- on other outlets you get a real IP, 137.138.*.*, right? And
that works as expected?
> > >To add to this, when other laptops
> > >connect to my wall outlet, they work properly.
Is the MAC address of your laptop registered with the CERN admins? Last time I
was there (which was several years ago, so my knowledge on this might be a bit
outdated), every device had to be registered and ratified by the net admins
before they would grant access to Internet. Until they do (it used to take
them a day or two to update their database), the device will obtain a "dummy"
IP number that is filtered by their firewall and you don't have access to
anything except the registration web page.
If you did register your machine, you should ask the admins over there to help
you out with your wall outlet. The following piece of log from
/var/log/messages should give them a clue:
Aug 30 15:59:55 kuru dhclient[23044]: DHCPREQUEST on eth2 to 255.255.255.255
port 67 (xid=0x7fd1f93c)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPNAK from 137.138.16.6
(xid=0x7fd1f93c)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPDISCOVER on eth2 to 255.255.255.255
port 67 interval 4 (xid=0x71ed1546)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPREQUEST on eth2 to 255.255.255.255
port 67 (xid=0x71ed1546)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPOFFER from 192.168.0.1
Aug 30 15:59:55 kuru dhclient[23044]: DHCPNAK from 137.138.16.6
(xid=0x71ed1546)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPNAK from 137.138.17.6
(xid=0x71ed1546)
Aug 30 15:59:55 kuru dhclient[23044]: DHCPACK from 192.168.0.1
(xid=0x71ed1546)
Aug 30 15:59:55 kuru dhclient[23044]: bound to 192.168.0.114 -- renewal in
33183 seconds.
In plain english, your machine first asks the server 137.138.16.6 for an IP
assignment (DHCPREQUEST). The server refuses (DHCPNAK). Then your machine asks
which dhcp servers are out there (DHCPDISCOVER), and asks anyone for an IP
assignment (DHCPREQUEST). Three servers respond: 137.138.16.6 and 137.138.17.6
refuse (DHCPNAK), while 192.168.0.1 accepts (DHCPACK) and gives you an
internal IP, which doesn't seem to be able to access the outside world.
I am not sure if this is a misconfiguration or implemented on purpose, but the
CERN admins need to figure out why both of the two 137.138 dhcp servers have
refused to give you an IP. This is the problem on their end of the wall
outlet. Your machine seems to be configured correctly and also behaves
correctly.
The guys at CERN usually know what they are doing, so the best bet would be to
ask them for help, they should certainly be able to fix this.
HTH, :-)
Marko
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