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Nikos Chantziaras 10-25-2008 12:31 AM

dhcpd uses fake MAC address
 
Nick Stinemates wrote:

On Sat, Oct 25, 2008 at 02:07:20AM +0300, Nikos Chantziaras wrote:
My router has big problems assigning the correct IPs to Gentoo boxes. If
the NIC in the box has a MAC address of, say, 01:00:12:11:41:49:1e,
dhcpd reports something else to router: ff:42:54:59:20:00:1c:21:e0:42:c2


Why is this happening and how do I tell dhcpd not to mess with the MAC
address it reports to DHCP servers?


Same experience here. I always thought it was a linux/windows
compatibility problem since that is where I noticed the problem first.


Nope, it only happens with the dhcpd of Gentoo. Other Linux boxes
report the correct MAC address.

Volker Armin Hemmann 10-25-2008 11:34 AM

dhcpd uses fake MAC address
 
On Samstag 25 Oktober 2008, Nikos Chantziaras wrote:
> Nick Stinemates wrote:
> > On Sat, Oct 25, 2008 at 02:07:20AM +0300, Nikos Chantziaras wrote:
> >> My router has big problems assigning the correct IPs to Gentoo boxes. If
> >> the NIC in the box has a MAC address of, say, 01:00:12:11:41:49:1e,
> >> dhcpd reports something else to router: ff:42:54:59:20:00:1c:21:e0:42:c2
> >>
> >> Why is this happening and how do I tell dhcpd not to mess with the MAC
> >> address it reports to DHCP servers?
> >
> > Same experience here. I always thought it was a linux/windows
> > compatibility problem since that is where I noticed the problem first.
>
> Nope, it only happens with the dhcpd of Gentoo. Other Linux boxes
> report the correct MAC address.

my dhcpd reports the right mac adress (when I try it), so it must be your
fault ;)

Nick Stinemates 10-25-2008 06:33 PM

dhcpd uses fake MAC address
 
On Sat, Oct 25, 2008 at 01:34:36PM +0200, Volker Armin Hemmann wrote:
> On Samstag 25 Oktober 2008, Nikos Chantziaras wrote:
> > Nick Stinemates wrote:
> > > On Sat, Oct 25, 2008 at 02:07:20AM +0300, Nikos Chantziaras wrote:
> > >> My router has big problems assigning the correct IPs to Gentoo boxes. If
> > >> the NIC in the box has a MAC address of, say, 01:00:12:11:41:49:1e,
> > >> dhcpd reports something else to router: ff:42:54:59:20:00:1c:21:e0:42:c2
> > >>
> > >> Why is this happening and how do I tell dhcpd not to mess with the MAC
> > >> address it reports to DHCP servers?
> > >
> > > Same experience here. I always thought it was a linux/windows
> > > compatibility problem since that is where I noticed the problem first.
> >
> > Nope, it only happens with the dhcpd of Gentoo. Other Linux boxes
> > report the correct MAC address.
>
> my dhcpd reports the right mac adress (when I try it), so it must be your
> fault ;)
>
>

Could it be a /etc/conf.d/net issue? Mind pasting yours?

Volker Armin Hemmann 10-25-2008 10:39 PM

dhcpd uses fake MAC address
 
On Samstag 25 Oktober 2008, Nick Stinemates wrote:
> On Sat, Oct 25, 2008 at 01:34:36PM +0200, Volker Armin Hemmann wrote:
> > On Samstag 25 Oktober 2008, Nikos Chantziaras wrote:
> > > Nick Stinemates wrote:
> > > > On Sat, Oct 25, 2008 at 02:07:20AM +0300, Nikos Chantziaras wrote:
> > > >> My router has big problems assigning the correct IPs to Gentoo
> > > >> boxes. If the NIC in the box has a MAC address of, say,
> > > >> 01:00:12:11:41:49:1e, dhcpd reports something else to router:
> > > >> ff:42:54:59:20:00:1c:21:e0:42:c2
> > > >>
> > > >> Why is this happening and how do I tell dhcpd not to mess with the
> > > >> MAC address it reports to DHCP servers?
> > > >
> > > > Same experience here. I always thought it was a linux/windows
> > > > compatibility problem since that is where I noticed the problem
> > > > first.
> > >
> > > Nope, it only happens with the dhcpd of Gentoo. Other Linux boxes
> > > report the correct MAC address.
> >
> > my dhcpd reports the right mac adress (when I try it), so it must be your
> > fault ;)
>
> Could it be a /etc/conf.d/net issue? Mind pasting yours?

yes, because I have a static ip. But it is the usual

config_eth0="... netmask 255.255.255.0"
routes_eth0="default via ..."
gateways_eth0="..."

so nothing special there.

Nikos Chantziaras 10-25-2008 10:53 PM

dhcpd uses fake MAC address
 
Volker Armin Hemmann wrote:

On Samstag 25 Oktober 2008, Nick Stinemates wrote:

On Sat, Oct 25, 2008 at 01:34:36PM +0200, Volker Armin Hemmann wrote:

my dhcpd reports the right mac adress (when I try it), so it must be your
fault ;)

Could it be a /etc/conf.d/net issue? Mind pasting yours?


yes, because I have a static ip. But it is the usual


config_eth0="... netmask 255.255.255.0"
routes_eth0="default via ..."
gateways_eth0="..."


so nothing special there.



If you have a static IP what do you need a dhcp daemon for? :P

Volker Armin Hemmann 10-26-2008 12:32 AM

dhcpd uses fake MAC address
 
On Sonntag 26 Oktober 2008, Nikos Chantziaras wrote:
> Volker Armin Hemmann wrote:
> > On Samstag 25 Oktober 2008, Nick Stinemates wrote:
> >> On Sat, Oct 25, 2008 at 01:34:36PM +0200, Volker Armin Hemmann wrote:
> >>> my dhcpd reports the right mac adress (when I try it), so it must be
> >>> your fault ;)
> >>
> >> Could it be a /etc/conf.d/net issue? Mind pasting yours?
> >
> > yes, because I have a static ip. But it is the usual
> >
> > config_eth0="... netmask 255.255.255.0"
> > routes_eth0="default via ..."
> > gateways_eth0="..."
> >
> > so nothing special there.
>
> If you have a static IP what do you need a dhcp daemon for? :P

I don't need it. But in our network most people use windows - and don't know
anything about computers. So they get their static ip assigned by dhcp. Once
in a while the server chokes - and that is one of the many reasons why I
usually don't use dhcp. There are a lot better ones, but if you really need
to know the details, ask off-list ;)

Nikos Chantziaras 10-26-2008 01:29 AM

dhcpd uses fake MAC address
 
Volker Armin Hemmann wrote:

On Sonntag 26 Oktober 2008, Nikos Chantziaras wrote:

Volker Armin Hemmann wrote:

On Samstag 25 Oktober 2008, Nick Stinemates wrote:

On Sat, Oct 25, 2008 at 01:34:36PM +0200, Volker Armin Hemmann wrote:

my dhcpd reports the right mac adress (when I try it), so it must be
your fault ;)

Could it be a /etc/conf.d/net issue? Mind pasting yours?

yes, because I have a static ip. But it is the usual

config_eth0="... netmask 255.255.255.0"
routes_eth0="default via ..."
gateways_eth0="..."

so nothing special there.

If you have a static IP what do you need a dhcp daemon for? :P


I don't need it. But in our network most people use windows - and don't know
anything about computers. So they get their static ip assigned by dhcp. Once
in a while the server chokes - and that is one of the many reasons why I
usually don't use dhcp. There are a lot better ones, but if you really need
to know the details, ask off-list ;)


Anyway, maybe it's not a dhcp problem but originates further down the
stack. Not sure what I'm looking for though :P

Iain Buchanan 10-29-2008 01:56 AM

dhcpd uses fake MAC address
 
Nikos Chantziaras wrote:

My router has big problems assigning the correct IPs to Gentoo boxes. If
the NIC in the box has a MAC address of, say, 01:00:12:11:41:49:1e,
dhcpd reports something else to router: ff:42:54:59:20:00:1c:21:e0:42:c2

Why is this happening and how do I tell dhcpd not to mess with the MAC
address it reports to DHCP servers?


what happens when you ping from the erroneous box to the dhcp server,
and sniff the actual traffic on the dhcp server to see what it sees.
Then ping a different box and see what that sees, etc.



--
Iain Buchanan <iaindb at netspace dot net dot au>

Any clod can have the facts, but having opinions is an art.
-- Charles McCabe

Mick 10-29-2008 09:49 AM

dhcpd uses fake MAC address
 
On Sunday 26 October 2008, Nikos Chantziaras wrote:
> Volker Armin Hemmann wrote:

> > I don't need it. But in our network most people use windows - and don't
> > know anything about computers. So they get their static ip assigned by
> > dhcp. Once in a while the server chokes - and that is one of the many
> > reasons why I usually don't use dhcp. There are a lot better ones, but
> > if you really need to know the details, ask off-list ;)
>
> Anyway, maybe it's not a dhcp problem but originates further down the
> stack. Not sure what I'm looking for though :P

I've posted a couple of weeks ago about the same thing
titled "net-misc/dhcpcd-4.0.1-r1 change of USE flags". I have since found
that the problem you observed essentially boils down to the router's dhcp
server implementation and the way it treats the client_identifier string.

The dhcpcd package complies with RFC2131 and generates and broadcasts a
unique device identification number for your NIC (DUID). DUID is the long
number you have posted, the tail end of which contains the MAC. The server
is meant to use this number (according to RFC4361, clause 6.3):
=============================================
DHCPv4 servers that conform to this specification MUST use the
'client identifier' option to identify the client if the client sends
it.
=============================================

All this is fine and dandy, if only the dhcp server in question could directly
correlate the dhcpcd generated DUID to your MAC. Unfortunately, many routers
won't. They will treat the static MAC settings as a different device than
that of the DUID and issue your PC with a different than the preselected
static IP address. You can run dhcpcd eth0 -T -d to verify what's happening
in your case, although a newly issued IP address which is different than the
preset static IP address is a giveaway.

More sophisticated routers allow you to set up on their CLI static LAN IP
addresses using the DUID string, instead of the client's MAC hardware
address.

Previous versions of dhcpcd had the vram USE flag which copied the hardware
address into the DUID string and the dhcp servers would happily recognise the
original network device, while using the DUID string. Now the vram flag is
gone. Therefore, if you cannot set up static IP addresses with your router's
CLI using the client_indentifier string (like e.g. on Cisco and
Adtran/Netvanta routers), the only other solution would be to set it on the
client side. That's an inconvenient solution if you have a laptop which
connects to all sort of networks with different LAN IP addresses/ranges. In
that case you may have to run ifconfig and route manually each time you
connect to a network.
--
Regards,
Mick

"Joshua Murphy" 10-30-2008 12:08 AM

dhcpd uses fake MAC address
 
On Wed, Oct 29, 2008 at 6:49 AM, Mick <michaelkintzios@gmail.com> wrote:
<snip>
> More sophisticated routers allow you to set up on their CLI static LAN IP
> addresses using the DUID string, instead of the client's MAC hardware
> address.
>
> Previous versions of dhcpcd had the vram USE flag which copied the hardware
> address into the DUID string and the dhcp servers would happily recognise the
> original network device, while using the DUID string. Now the vram flag is
> gone. Therefore, if you cannot set up static IP addresses with your router's
> CLI using the client_indentifier string (like e.g. on Cisco and
> Adtran/Netvanta routers), the only other solution would be to set it on the
> client side. That's an inconvenient solution if you have a laptop which
> connects to all sort of networks with different LAN IP addresses/ranges. In
> that case you may have to run ifconfig and route manually each time you
> connect to a network.
> --
> Regards,
> Mick
>

Or, actually, you could just give in and use a different dhcp
client... one more forgiving of less RFC compliant servers. Just
winging an admittedly untested idea... try "busybox udhcpc" and see if
it gives you the right IP... and if so, try emerging net-misc/udhcp
(different from BB's built in, but it's worked in all the same places
as BB's has for me, which includes some very cheap routers) and
setting your conf.d/net to use it over other clients. ( modules=(
"udhcpc" ) )

--
Poison [BLX]
Joshua M. Murphy


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