Direct connection to Ubuntu does not work

[Samtheman]

Hi,

With modem in router, DHCP is working perfectly.

However, when I try put the cable directly into my PC (Ubuntu Server), it does not work

It does not get a DHCP response, yet on the router it does. I know the modem is the main MAC connected to the router, but do they filter connected devices somehow?

Modem is an old one (none superhub, but not motorola either).

c  2 19:27:57 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 18
Dec  2 19:28:15 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 15
Dec  2 19:28:30 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 15
Dec  2 19:28:45 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 8
Dec  2 19:28:53 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 16
Dec  2 19:29:09 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 15
Dec  2 19:29:24 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 19
Dec  2 19:29:43 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 8
Dec  2 19:29:51 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 9
Dec  2 19:30:00 precise dhclient: DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 11
Dec  2 19:30:11 precise dhclient: No DHCPOFFERS received.

My /etc/network/interfaces


auto eth1
iface eth1 inet dhcp
mtu 1500
pre-up iptables-restore </etc/iptables.rules

I don't think the issue is iptables-rules, but willing to post them

[Matthew]

You cannot just unplug and replug. You need to power down your modem and back on again for it to work.

[Samtheman]

Oh -- is this only due to changes of MAC?

[Matthew]

I do not know the ins and outs but yes I think so.

[Samtheman]

ok that helped

Now to look at iptables and figure why it's not routing!