Modifying the ip address of a Server

To modify the ipaddress permanently you have to edit the file:
/etc/hosts or /etc/inet/ipnodes (which is a link to /etc/hosts).

And set there the hostname and the IP address like:
127.0.0.1 localhost
10.10.10.20 solln

Then you have to reboot. You can also change it with ifconfig (like in Linux), first obtain the ethernet card address:
-bash-3.00# ifconfig -a
lo0: flags=2001000849 mtu 8232 index 1
inet 127.0.0.1 netmask ff000000
e1000g0: flags=1000843 mtu 1500 index 2
inet 10.10.10.21 netmask ff000000 broadcast 10.255.255.255
ether 0:c:29:2d:30:5

Then, carefully, modify the address:
# ifconfig e1000g0 10.10.10.20

You will probably loose the connection if you are doing this remotely, so, again, at your own risk.