If you have ifconfig and netstat -in . Please post your output. Also, are you saying that you configure your lan card to come up at boot time, but there is a configuration file that you must modify too.
On my HPUX, there is a file /etc/rc.config.d/netconf which defines the lan number and IP address.
You may have a similar config file.
It would help if we knew a little about your system OS, config.