The ISP guys called up and said some port was changed at their end and
hence the problem, but i would like to know once there was no gateway
route/path on the Internet Server, how come the LAN users were able to
browse from their workstation after the port was changed at the BSNL end
before me running the firewall Script which starts the adsl connection and
assigns IP to the ppp0 interface, this boggles my mind.
During that time when this problem occurred, following was observed on the
ifconfig eth1 had its IP set OK (i.e our internal LAN IP)
ifconfig ppp0 had NO IP assigned (Public IP-Dynamic) since as BSNL said
they were changing some port at their end.
IP forwarding was OK.
Since there is no black magic involved ;-) , it is most likely that a
route was available which went un-noticed. Sometimes with cable internet
which uses no dhcp and only pppoe, it so happens that dhcp does work
sometimes and even allows browsing without pppoe. I have noticed this
with new installations or after replacement of ethernet cards. However
after the new mac id is locked at the cablenet provider end, there is no
dhcp and net access is only through pppoe. Those familiar with setup of
pppoe Servers may be able to shed more light on this phenomenon.