Ubuntu as router for MAC ? Avahi vs Dhcp

[ktt]

Hello,

I would like my Ubuntu machine to share files with MAC and to act as a router. I established Ubuntu+MAC OSX connection for file sharing and available services advertising as it was described
http://www.kremalicious.com/2008/06/...achine-volume/
It works nicely.
I would like to make my Ubuntu machine as internet router for my MAC as well, but here curiosities begin: eth0 has no IP address, dhcp3-server conflicts with Avahi. I have Flash media server on my Ubuntu machine, so it's important to have it. I can use static IP adress, but Avahi will not work. 

This is my ifconfig dump:

eth0 Link encap:Ethernet HWaddr 00:1b:38:0a:dd:26
inet6 addr: fe80:xbxff:fe0a:dd26/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:34 errors:0 dropped:0 overruns:0 frame:0
TX packets:27 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5572 (5.5 KB) TX bytes:5948 (5.9 KB)
Interrupt:19

eth0:avahi Link encap:Ethernet HWaddr 00:1b:38:0a:dd:26
inet addr:169.254.XXX..XX Bcast:169.254.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:19

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:21 errors:0 dropped:0 overruns:0 frame:0
TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1284 (1.2 KB) TX bytes:1284 (1.2 KB)

wimax1 Link encap:Ethernet HWaddr 00:24:90:83:5b:15
inet addr:XX.XXX.XXX.135 Bcast:89.XXX.XXX.XXX Mask:255.255.255.0
inet6 addr: fe80::224:90ff:fe83:5b15/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1386 Metric:1
RX packets:17720 errors:0 dropped:0 overruns:0 frame:0
TX packets:18275 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:500
RX bytes:14928610 (14.9 MB) TX bytes:5114526 (5.1 MB)

Thank you in advance.

Kioshin