I have changed in /etc/hosts follow line:
...
192.168.1.1 server.riv66.com server
...

and /etc/resolve.conf:
...
name server 192.168.1.1
...

I have rebooted server and client.

Ping from server:
[root@server root]# ping -c 3 pos1
PING pos1.riv66.com (192.168.1.11) from 192.168.1.0 : 56(84) bytes of data.
From server.riv66.com (192.168.1.0) : Destination Host Unreachable
From server.riv66.com (192.168.1.0) : Destination Host Unreachable
From server.riv66.com (192.168.1.0) : Destination Host Unreachable

--- pos1.riv66.com ping statistics ---
3 packets trasmitted, 0 packets received, +3 errors, 100% packets loss
Server has not changed configuration (report always 192.168.1.0).

Ping form client:
[root@pos1 root] # ping -c 3 server
PING server.riv66.com (192.168.1.1) from 192.168.1.10 : 56(84) bytes of data.
From 192.168.1.10: Destination Host Unreachable
From 192.168.1.10: Destination Host Unreachable
From 192.168.1.10: Destination Host Unreachable

--- server.riv66.com ping statistics ---
3 packets trasmitted, 0 packets received, +3 errors, 100% packets loss
192.168.1.10?!? But i have assigned 192.168.1.11 to client.

I had checked files, but configuration is reported correctly on this post.
Can you help me?
Thanks.