Ultra E150 Solaris 2.5.1 Oracle server. was working fine, then started losing network connection. I can see in messages file that it was complaining about another device using its ip address. Though not any longer, though I wonder if that was a red herring. My IT guys have now re-reserved its ip address on the dhcp server. I have restarted it several times but it won't talk to the network. I tried changing its ip address to another reserved one, but Oracle complains, the ip must be embedded in that somewhere. Should the ethernet cable socket flash when connected on this hardware? it doesn't. I tried a different cable, direct into a different hub.

You should not have changed anything on the system. You should have disconnected and reconnect the cable or worst case you should have rebooted the system once since you found out the conflicting IP and isolating it

Thanks Incredible. Trying a different cable was the first thing tried, then a different port, with no success. After seeing the ip conflict message and fixing the reserved ip address, the server was restarted prior to changing anything else. It did not fix the problem. Then I only changed the IP address and its now changed back. The behaviour is still identical to what it was before. The messages file does not complain about an ip conflict since that was fixed. So I haven't actually isolated teh problem yet, though it may have been triggerred by the ip conflict.

Was this reverted back?

Yes the ip address is reserved as what it was originally on DHCP and I've reverted the etc/hosts file back to its original address.

where is your oracle communicating from? Am I correct to say that you are not able to ping your server remotely as before? No outputs, so Im having difficulty to figure out where the actual problem is

I am unable to ping to this server from the network, - nor from this server to the network.
Oracle is installed on this server.