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Old 01-18-2008, 04:09 PM
"Marko Kocić"
 
Default Net / dhcp (miss)behaviour

I'm running gentoo on my dual boot windows laptop.

I use dhcp to connect to the the internet through cable modem.
Sometimes (in the evenings) it just fails to automatically obtain IP
address from dhcp server (timeouts).
I tried different settings in /etc/conf.d/net file (timeout and
different dhcpc options) and switching between dhclient and dhcpd, but
with no luck.

When I reboot to windows it just works. I contacted my ISP, but they
said they don't give support for Linux.

Is there a way to configure dhcp/dhclient to behave exactly like DHCP
in Windows XP?

Regards,
Marko
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gentoo-user@lists.gentoo.org mailing list
 
Old 01-18-2008, 04:50 PM
Alan McKinnon
 
Default Net / dhcp (miss)behaviour

On Friday 18 January 2008, Marko Kocić wrote:
> I'm running gentoo on my dual boot windows laptop.
>
> I use dhcp to connect to the the internet through cable modem.
> Sometimes (in the evenings) it just fails to automatically obtain IP
> address from dhcp server (timeouts).
> I tried different settings in /etc/conf.d/net file (timeout and
> different dhcpc options) and switching between dhclient and dhcpd,
> but with no luck.
>
> When I reboot to windows it just works. I contacted my ISP, but they
> said they don't give support for Linux.
>
> Is there a way to configure dhcp/dhclient to behave exactly like DHCP
> in Windows XP?

Where is the dhcp server? On the cable provider's network, or on the
modem itself?

I have found that dhcp can do weird stuff sometimes and Windows client
don't always follow the standard method. Then again, what else is new?

My first diagnostic step would be to get another machine on the network
and sniff dhcp traffic when using Windows and Gentoo to see what the
difference is.

alan


--
Alan McKinnon
alan dot mckinnon at gmail dot com
--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-18-2008, 05:03 PM
"Marko Kocić"
 
Default Net / dhcp (miss)behaviour

On Jan 18, 2008 6:50 PM, Alan McKinnon <alan.mckinnon@gmail.com> wrote:
>
> On Friday 18 January 2008, Marko Kocić wrote:
> > I'm running gentoo on my dual boot windows laptop.
> >
> > I use dhcp to connect to the the internet through cable modem.
> > Sometimes (in the evenings) it just fails to automatically obtain IP
> > address from dhcp server (timeouts).
> > I tried different settings in /etc/conf.d/net file (timeout and
> > different dhcpc options) and switching between dhclient and dhcpd,
> > but with no luck.
> >
> > When I reboot to windows it just works. I contacted my ISP, but they
> > said they don't give support for Linux.
> >
> > Is there a way to configure dhcp/dhclient to behave exactly like DHCP
> > in Windows XP?
>
> Where is the dhcp server? On the cable provider's network, or on the
> modem itself?

On cable providers network.

> I have found that dhcp can do weird stuff sometimes and Windows client
> don't always follow the standard method. Then again, what else is new?

> My first diagnostic step would be to get another machine on the network
> and sniff dhcp traffic when using Windows and Gentoo to see what the
> difference is.

I can't do that, cause I don't have switch/hub, just a cable modem directly
conencted to laptop.

I was looking for some magic "enable windows emulation mode" for dhcp.

> alan
>

Thanks,
Marko
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Old 01-18-2008, 05:17 PM
"Marko Kocić"
 
Default Net / dhcp (miss)behaviour

> I never used cable modem and don't know how it connects to the PC, so I
> might be saying something completely wrong here,

Regular network cable going directly from cable modem to laptop.

> but can't you sniff the
> traffic directly from the laptop by capturing packets on the interface
> connected to the cable modem?

I can do that when interface is up is up and running.
But it is /etc/init.d/net.eth0 that is failing because of dhcp error.

What should I use? Ethereal? What should I look for?
--
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Old 01-18-2008, 05:24 PM
Etaoin Shrdlu
 
Default Net / dhcp (miss)behaviour

On Friday 18 January 2008, Marko Kocić wrote:

> > My first diagnostic step would be to get another machine on the
> > network and sniff dhcp traffic when using Windows and Gentoo to see
> > what the difference is.
>
> I can't do that, cause I don't have switch/hub, just a cable modem
> directly conencted to laptop.

I never used cable modem and don't know how it connects to the PC, so I
might be saying something completely wrong here, but can't you sniff the
traffic directly from the laptop by capturing packets on the interface
connected to the cable modem?
--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-18-2008, 05:27 PM
Kevin
 
Default Net / dhcp (miss)behaviour

On Jan 18, 2008 12:17 PM, Marko Kocić <marko.kocic@gmail.com> wrote:

> I never used cable modem and don't know how it connects to the PC, so I
> might be saying something completely wrong here,

Regular network cable going directly from cable modem to laptop.

> but can't you sniff the

> traffic directly from the laptop by capturing packets on the interface
> connected to the cable modem?

I can do that when interface is up is up and running.
But it is /etc/init.d/net.eth0 that is failing because of dhcp error.


What should I use? Ethereal? What should I look for?
--
gentoo-user@lists.gentoo.org mailing list




You can try Ethereal (which now goes by wireshark).** Question,* when it fails have you logged in and done a /etc/init.d/net stop / start?*** Just curious if it will "force" itself up.
 
Old 01-18-2008, 05:38 PM
"Marko Kocić"
 
Default Net / dhcp (miss)behaviour

> Actually, as long as the interface is up, you can sniff traffic even if
> it does not have an IP address. Emerge wireshark (somehow...), do (as
> root) an "ip link set eth0 up" (or "ifconfig eth0 up") and run
> wireshark. Start capturing packets, run dhcpcd from the command line (or
> whatever DHCP client you use), and see what goes on the wire. You should
> see DHCP discovery/offer/request messages, or maybe not all of them if
> things are not working correctly. For each DHCP packet, look at the DHCP
> payload details from wireshark (you can save the capture for later
> viewing too).
>
> Then, start windows, install wireshark for windows, and do the same. To
> force a DHCP negotiation in windows, open a command prompt and issue
> an "ipconfig /release" followed by an "ipconfig /renew" (IIRC). Look at
> the traffic captured after the /renew command, and look for obvious or
> blatant differences between windows and linux in DHCP packets of the
> same kind.

Thanks for the info. I'll try that.

Also, I just found by googling that there is dhcp client called
net-misc/pump which
have --win-client-ident option. I'll try that too.

Regards,
Marko
--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-18-2008, 05:48 PM
Etaoin Shrdlu
 
Default Net / dhcp (miss)behaviour

On Friday 18 January 2008, Marko Kocić wrote:

> > I never used cable modem and don't know how it connects to the PC,
> > so I might be saying something completely wrong here,
>
> Regular network cable going directly from cable modem to laptop.
>
> > but can't you sniff the
> > traffic directly from the laptop by capturing packets on the
> > interface connected to the cable modem?
>
> I can do that when interface is up is up and running.
> But it is /etc/init.d/net.eth0 that is failing because of dhcp error.
>
> What should I use? Ethereal? What should I look for?

Actually, as long as the interface is up, you can sniff traffic even if
it does not have an IP address. Emerge wireshark (somehow...), do (as
root) an "ip link set eth0 up" (or "ifconfig eth0 up") and run
wireshark. Start capturing packets, run dhcpcd from the command line (or
whatever DHCP client you use), and see what goes on the wire. You should
see DHCP discovery/offer/request messages, or maybe not all of them if
things are not working correctly. For each DHCP packet, look at the DHCP
payload details from wireshark (you can save the capture for later
viewing too).

Then, start windows, install wireshark for windows, and do the same. To
force a DHCP negotiation in windows, open a command prompt and issue
an "ipconfig /release" followed by an "ipconfig /renew" (IIRC). Look at
the traffic captured after the /renew command, and look for obvious or
blatant differences between windows and linux in DHCP packets of the
same kind.
--
gentoo-user@lists.gentoo.org mailing list
 
Old 01-18-2008, 10:31 PM
Mick
 
Default Net / dhcp (miss)behaviour

On Friday 18 January 2008, Marko Kocić wrote:
> > Actually, as long as the interface is up, you can sniff traffic even if
> > it does not have an IP address. Emerge wireshark (somehow...), do (as
> > root) an "ip link set eth0 up" (or "ifconfig eth0 up") and run
> > wireshark. Start capturing packets, run dhcpcd from the command line (or
> > whatever DHCP client you use), and see what goes on the wire. You should
> > see DHCP discovery/offer/request messages, or maybe not all of them if
> > things are not working correctly. For each DHCP packet, look at the DHCP
> > payload details from wireshark (you can save the capture for later
> > viewing too).
> >
> > Then, start windows, install wireshark for windows, and do the same. To
> > force a DHCP negotiation in windows, open a command prompt and issue
> > an "ipconfig /release" followed by an "ipconfig /renew" (IIRC). Look at
> > the traffic captured after the /renew command, and look for obvious or
> > blatant differences between windows and linux in DHCP packets of the
> > same kind.
>
> Thanks for the info. I'll try that.
>
> Also, I just found by googling that there is dhcp client called
> net-misc/pump which
> have --win-client-ident option. I'll try that too.

I wonder if my similar problem is related to what you report here: I am using
dhcpcd and ifplug with my ADSL router, which acts as the dhcp server on my
LAN. For some reason ifplug does not always manage to get an IP address from
the router and I end up with an APIPA address. /etc/init.d/net.eth0
stop/start gets it going again. This problem only occurs if I disconnect and
then reconnect the ethernet cable. No such problem exists when I boot the
machine with the cable already connected to the NIC. I haven't changed
timeouts or anything else from the dhcpcd defaults. I have always attributed
this problem to a somewhat slow dhcp server on the router.

As a note: WinXP machines do not have any such problem. Even though they may
end up with a APIPA address, they will in minute or so drop it and acquire a
10.10.10.XXX domain address from the router. dhcpcpd does not seem to have
this flexibility.
--
Regards,
Mick
 
Old 01-19-2008, 09:09 PM
"Marko Kocić"
 
Default Net / dhcp (miss)behaviour

> I wonder if my similar problem is related to what you report here: I am using
> dhcpcd and ifplug with my ADSL router, which acts as the dhcp server on my
> LAN. For some reason ifplug does not always manage to get an IP address from
> the router and I end up with an APIPA address. /etc/init.d/net.eth0
> stop/start gets it going again. This problem only occurs if I disconnect and
> then reconnect the ethernet cable. No such problem exists when I boot the
> machine with the cable already connected to the NIC. I haven't changed
> timeouts or anything else from the dhcpcd defaults. I have always attributed
> this problem to a somewhat slow dhcp server on the router.

It is similar, with a difference that /etc/init.d/net.eth0 restart
doesn't help. I tried
enlarging timeout but with no help.

>
> As a note: WinXP machines do not have any such problem. Even though they may
> end up with a APIPA address, they will in minute or so drop it and acquire a
> 10.10.10.XXX domain address from the router. dhcpcpd does not seem to have
> this flexibility.

I noticed that in most cases after I boot to windows, when I reboot
back to linux I can't connect.
When I reboot back to windows, net is up.

When it fails I noticed that it send DHCP requests, but doesn't get a response.

I tried dhclient, dhcpd and pump, and the results are allways the
same. It happens in the evenings, when internet traffic is high.
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