HP-UX nslookup is quite special; it shows the host lookup order.
If there isn't yet a /etc/nsswitch.conf then create one with a dns entry; the following command can do it
sed '/^hosts/...
If the ports of your router are 100MB full duplex it should be the same HP-UX side, avoid auto unless you have GB...
you can checkout with lanadmin command
Did you use setparms to configure your IP...