AW: bootp problems

AW: bootp problems

[Jochen Vogel]

> > [DialIn]2.2.2.2----2.2.2.1[FW]1.1.1.1---1.1.1.2[DHCP]
> >
> > the DialIn tries to get an IP from the DHCP Server.
> 
> You need a DHCP relay on the 2 network to do this.
> 
> DHCP requests do not cross routers (they are ethernet broadcasts).

Hi antony,

The DialIN should play Relay

FIRST the DialIn try it DIRECTLY to the DHCP Server
with tcpdump on 2.1 i can see 0.0.0.0:68 > 1.1.1.2:67
It doesnt work and i CANT see any entry in the iptables log

SECOND the DialIn try it with BROADCAST
with tcpdump on 2.1 i can see 0.0.0.0:68 > 255.255.255.255:67
It doesnt work and i CAN see an entry in the iptables log

Thx for more informations
Jo

Re: AW: bootp problems

[Antony Stone]

On Wednesday 07 April 2004 8:50 am, Jochen Vogel wrote:

> > > [DialIn]2.2.2.2----2.2.2.1[FW]1.1.1.1---1.1.1.2[DHCP]
> > >
> > > the DialIn tries to get an IP from the DHCP Server.
> >
> > You need a DHCP relay on the 2 network to do this.
> >
> > DHCP requests do not cross routers (they are ethernet broadcasts).
>
> Hi antony,
>
> The DialIN should play Relay
>
> FIRST the DialIn try it DIRECTLY to the DHCP Server
> with tcpdump on 2.1 i can see 0.0.0.0:68 > 1.1.1.2:67
> It doesnt work and i CANT see any entry in the iptables log

How is Linux supposed to route a reply packet from 1.1.1.2:67 back to 
0.0.0.0:68?

> SECOND the DialIn try it with BROADCAST
> with tcpdump on 2.1 i can see 0.0.0.0:68 > 255.255.255.255:67
> It doesnt work and i CAN see an entry in the iptables log

Broadcasts do not cross routers.   That is nothing to do with netfilter (and 
no, you cannot create any netfilter rules to make a broadcast cross to the 
other side).

Maybe your firewall needs to be a bridge?

Regards,

Antony.

-- 
Christmas was just an opportunity to upgrade to kernel 2.6 while no-one was 
around to notice the downtime.

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