after changing IP and ifup --all, SIOCADDRT: Invalid argument

I have debian 2.2, kernel 2.2.19. I had to change the configuration of network (I mean I had to change IP, netmask, gateway and so on). I did the following three steps. 1step 'ifdown --all' 2step ' I changed the file /etc/network/interfaces' 3step 'ifup --all' after the 3step i got the following

after changing IP and ifup --all, SIOCADDRT: Invalid argument

I have debian 2.2, kernel 2.2.19. I had to change the configuration of network (I mean I had to change IP, netmask, gateway and so on). I did the following three steps. 1step 'ifdown --all' 2step ' I changed the file /etc/network/interfaces' 3step 'ifup --all' after the 3step i got the following

how to figure out the gateway number?

I have debian 3.0. I have to change the configuration of network (I mean I have to change IP, netmask and so on). I know my IP address, netmask, broadcast. Is there a way to figure out the network and gateway number? Is it enough to do the following three steps?: 1step 'ifdown --all' 2step ' to