Failure to acquire IP over DHCP
 

Hi,

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. To add to this, when other laptops
connect to my wall outlet, they work properly.

This is a dump of my network connection (with DHCP enabled):
<http://pastebin.com/7bsXDMBP>. And the relevant bits from
/var/log/messages (when I get assigned the wrong IP):
<http://pastebin.com/9eZTprqk>

Any thoughts are welcome.

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Failure to acquire IP over DHCP
 

On 08/30/2012 10:36 AM, Suvayu Ali wrote:

Hi,

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. To add to this, when other laptops
connect to my wall outlet, they work properly.

This is a dump of my network connection (with DHCP enabled):
<http://pastebin.com/7bsXDMBP>. And the relevant bits from
/var/log/messages (when I get assigned the wrong IP):
<http://pastebin.com/9eZTprqk>


What is the IP subnet that DHCP hands out? Is it on a different subnet
from 192.168.0.x?


Sounds almost like the MAC address of your laptop has been assigned an
IP from the DHCP server. Why that keeps from getting internet access
depends on the subnet question above, methinks.




--

Mark Haney
Software Developer/Consultant
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Linux marius.homelinux.org 3.5.1-1.fc17.x86_64 GNU/Linux
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Failure to acquire IP over DHCP
 

On Thu, Aug 30, 2012 at 10:43:59AM -0400, Mark Haney wrote:
> On 08/30/2012 10:36 AM, Suvayu Ali wrote:
> >Hi,
> >
> >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. To add to this, when other laptops
> >connect to my wall outlet, they work properly.
> >
> >This is a dump of my network connection (with DHCP enabled):
> ><http://pastebin.com/7bsXDMBP>. And the relevant bits from
> >/var/log/messages (when I get assigned the wrong IP):
> ><http://pastebin.com/9eZTprqk>
>
> What is the IP subnet that DHCP hands out? Is it on a different subnet from
> 192.168.0.x?
>

My understanding of networks is next to nothing; by subnet do you mean
the netmask field as reported by ifconfig? If so I have quoted that
below:

eth2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.114 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::f2de:f1ff:fe37:c76c prefixlen 64 scopeid 0x20<link>
ether f0:de:f1:37:c7:6c txqueuelen 1000 (Ethernet)
RX packets 1465427 bytes 2094516052 (1.9 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 717576 bytes 56236036 (53.6 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 20 memory 0xf2500000-f2520000

> Sounds almost like the MAC address of your laptop has been assigned an IP
> from the DHCP server. Why that keeps from getting internet access depends
> on the subnet question above, methinks.
>

--
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Failure to acquire IP over DHCP
 

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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Failure to acquire IP over DHCP
 

On Thu, Aug 30, 2012 at 9:36 AM, Suvayu Ali <fatkasuvayu+linux@gmail.com> wrote:
> Hi,
>
> 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. To add to this, when other laptops
> connect to my wall outlet, they work properly.
>...

I assume by "wall outlet" you mean an RJ45 port.

I assume you're using Fedora. Which one? F16, F17?

Could you post the output of two commands:
# ip addr show
# ip route show

Do it for each of the two cases:
1. When you cannot access the internet (and you get the internal IP
192.168.0.114)
2. When you can access the internet (you say that everything works
when you use
any other wall outlet).

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Dale Dellutri
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Failure to acquire IP over DHCP
 

Once, long ago--actually, on Thu, Aug 30, 2012 at 11:24:58AM CDT--Marko Vojinovic (vvmarko@gmail.com) said:
> 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, ...

I would bet dollars to donuts they don't intend for that RFC1918 address to
be out there. It'd be extremely sloppy to have it on the same segment as
the 137.138 addresses; it's more likely something they don't intend to run
a DHCP server that's doing so anyway.


> ...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.

It's very common these days to have the switches require a new MAC address
to be authorized. Whatever segment you're plugging into probably doesn't
"know" the MAC address of your machine.

> The guys at CERN usually know what they are doing, ...

You'd certainly hope so!

> ...so the best bet would be to ask them for help, they should certainly
> be able to fix this.

And they'd probably be happy to know about that RFC1918 DHCP server, too.

Cheers,
--
Dave Ihnat
dihnat@dminet.com
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Failure to acquire IP over DHCP
 

On 08/30/2012 11:01 AM, Suvayu Ali wrote:

On Thu, Aug 30, 2012 at 10:43:59AM -0400, Mark Haney wrote:




What is the IP subnet that DHCP hands out? Is it on a different subnet from
192.168.0.x?



My understanding of networks is next to nothing; by subnet do you mean
the netmask field as reported by ifconfig? If so I have quoted that
below:

eth2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.0.114 netmask 255.255.255.0 broadcast 192.168.0.255


Well, the netmask is part of the subnet equation. Maybe I should have
queried you on your level of network knowledge. My apologies for
over-talking it.


The subnet for the other devices IPs, is it different from 192.168.0.X
your laptop is getting? Such as 172.16.0.x Or even 192.168.1.X (X being
the part of the IP that identifies a specific device.


Does that help clarify?





--

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Failure to acquire IP over DHCP
 

On 08/30/2012 12:24 PM, Marko Vojinovic wrote:

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




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.



I may be a bit thick here, but I see no reference to the OP having any
relation to CERN minus the public IP subnet the DHCP client is
requesting an IP from.



Mark Haney
Software Developer/Consultant
AB Emblem
markh@abemblem.com
Linux marius.homelinux.org 3.5.1-1.fc17.x86_64 GNU/Linux
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Failure to acquire IP over DHCP
 

On 08/30/2012 10:39 AM, Mark Haney wrote:

I may be a bit thick here, but I see no reference to the OP having any
relation to CERN minus the public IP subnet the DHCP client is
requesting an IP from.


It's not obvious, but a little checking will show that CERN owns
137.138.x.y.

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Failure to acquire IP over DHCP
 

On 08/30/2012 01:54 PM, Joe Zeff wrote:

On 08/30/2012 10:39 AM, Mark Haney wrote:

I may be a bit thick here, but I see no reference to the OP having any
relation to CERN minus the public IP subnet the DHCP client is
requesting an IP from.


It's not obvious, but a little checking will show that CERN owns
137.138.x.y.


That much I got, but that may just be a config error on the laptop
rather than an association with CERN. I mean, they are public DHCP
addresses. So unless he works for them, or what have you, that won't
work.


I'm not flaming, I'm just trying to make a point that he may not be
involved with CERN, so why should that matter?



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