Hi Phil and Dieter
As someone already explained on this list:
What does "kernel: martian source aabbccdd for 11223344, dev eth0" mean?
These are packets that Linux does not expect from the direction they came from (i.e. packets from internal hosts coming in on the external interface). The cause is probably a misconfigured machine on your LAN. You can turn off logging those packets via /proc/sys/net/ipv4/conf/*interface*/log_martians which is documented in /usr/src/linux/Documentation/proc.txt
...or you have got no default route to your ISP's IP, especially if you have a PPP connection to the ISP. IPPP seems to drop default routes if you do not place a '-defaultroute' in /etc/ppp/options.ippp0 (I found this out the hard way this weekend. Perhaps the normal PPPD does the same?) Bye, Jürgen