When eth0 is set to static IP or DHCP then eth0:avahi looses it's local connections

[Georgios Kolomvos]

My ubuntu 7.10 pc connects to the Internet through a USB ADSL modem 
(ppp0). I want to share this Internet connection with a windows vista pc 
that connects to my ubuntu pc with a crossover ethernet cable. This 
local connection seems to work fine since both PCs see each other. The 
ethernet interface used by the ubuntu pc for the local connection is 
eth:avahi and it works fine as long as the setting of eth0 is "enable 
roaming mode" (it is not possible to set any settings on eth:avahi from 
Network Tools because "the interface does not exist..."). But in this 
case (when eth0 is set to "enable roaming mode"), eth0 does not have any 
IP address (Network manager shows that it has 0.0.0.0 as IP address). So 
when i try to start a firewall through Firestarter (so that i could 
"Enable Internet connection sharing"), the firewall cannot start because 
"The device eth0 is not ready" (it is logical since it's IP address is 
0.0.0.0).

When i try to set eth0 to static IP or DHCP, then the firewall Starts 
nicely but interface eth0:avahi looses its IP address and the local 
connection with the windows pc is lost. It seems that eth0:avahi 
interface works properly only when the setting for eth0 is "enable 
roaming mode" (in this case there isn't any entry for eth0 in 
/etc/network/interfaces file).

I have read a lot about "ethX:avahi" bugs and problems on the Internet 
bit i haven't solved the problem yet.

Does anyone has any idea about what is happening here and what else 
should i try?
thank you for reading my message

Georgios Kolomvos
Patras, Greece

P.S. ifconfig output follows to help you understand the problem better

ubuntu-pc:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 00:16:E6:84:BE:4C 
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:707 errors:0 dropped:0 overruns:0 frame:0
          TX packets:201 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:55521 (54.2 KB)  TX bytes:37940 (37.0 KB)
          Interrupt:16

eth0:avah Link encap:Ethernet  HWaddr 00:16:E6:84:BE:4C 
          inet addr:169.254.167.197  Bcast:169.254.255.255  Mask:255.255.0.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:16

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:112 errors:0 dropped:0 overruns:0 frame:0
          TX packets:112 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:9416 (9.1 KB)  TX bytes:9416 (9.1 KB)

ppp0      Link encap:Point-to-Point Protocol 
          inet addr:77.49.12.191  P-t-P:194.219.252.143  
Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:2898 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2729 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:1970909 (1.8 MB)  TX bytes:283584 (276.9 KB)

vmnet1    Link encap:Ethernet  HWaddr 00:50:56:C0:00:01 
          inet addr:192.168.219.1  Bcast:192.168.219.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fec0:1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:199 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

vmnet8    Link encap:Ethernet  HWaddr 00:50:56:C0:00:08 
          inet addr:172.16.71.1  Bcast:172.16.71.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fec0:8/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:199 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)