Set /etc/hosts

On RT System Editor of Eclipse, Name Server View may not become effective.
It is avoidable by commenting out the IPv6 item of /etc/hosts.

% sudo gedit /etc/hosts

Example: /etc/hosts
127.0.0.1 localhost
127.0.1.1 yourservername # (note: your host name)

1. The following lines are desirable for IPv6 capable hosts
2. ::1 localhost ip6-localhost ip6-loopback
3. fe00::0 ip6-localnet
4. ff00::0 ip6-mcastprefix
5. ff02::1 ip6-allnodes
6. ff02::2 ip6-allrouters
7. ff02::3 ip6-allhosts