Why is my Linux Server slow?

Following can cause a Linux server to slow down when connected or not connected to a Network.

a)DNS unreachable or invalid:

the /etc/resolv.conf file contains a DNS server not reachable by the Linux server or invalid DNS. To change the DNS type PICO /etc/resolv.conf (PICO works like the Notepad program in Windows). Backspace the old DNS and enter the new DNS. To Use the hosts file for DNS resolution when no DNS server is available, use nameserver ...
To save the file in PICO type Ctrl+X then press Y and then press Enter

b)Permissions for the /etc/resolv.conf file are not set correctly:

you may set the permissions by typing
chmod 755 /etc/resolv.conf
or you can delete the /etc/resolv.conf file and recreate it by typing rm /etc/resolv.conf and then recreate it by using PICO /etc/resolv.conf

c)If the server is using the /etc/HOSTS file, the file may not have an entry that the Linux server is looking for:

The Linux server may be looking for tek-tips.com but cannot resolve the IP using the HOSTS file because that entry is not in the HOSTS file. Use PICO /etc/HOSTS and enter any additional entries.

d)The server may need to be restarted

e)The Network file may be missing a hostname or other information
pico /etc/sysconfig/network
The line HOSTNAME= needs to have a hostname after it
HOSTNAME=helper.tek-tips.com
Also check the GATEWAY= line for the correct gateway
pico /etc/sysconfig/network-scripts/ifcfg-eth0
Check IPADDR= and NETMASK= for the correct IP address and Subnet Mask

experts recommends to compare the network setting from a working machine to the problem machine.