your question seems to be a continuation to this so u could have just put it there rather than starting a new thread.
anyways, if u have now managed to get it connected thru eternet (i assume u added a lan card?) then all u have to do is make sure that modem is set to connect thru pppoe. then in you network settings assign an ip to your computer like 192.168.1.3 or if the modem has dhcp enabled then set your comp to obtain an ip automatically. put in the dns provided by mtnl(or just 192.168.1.1 will do). thats it, you should be good to go
i have never used sabayon .. in ubuntu however it is pretty straight forward (i was guessing u would know about these settings in sabayon)
i went thru their support forum and this is what i have found
(it seems that sabayon has some glitch due to witch it has trouble handling static ip addresses so the users have to follow the steps described in the link provided)
if i were you then i would switch to another distro which is more mainstream
best of luck..
EDIT- i read a little more and found out that if u just set up your modem to use dhcp then sabayon will aquire an address automatically without any problems. so try doing that