ifconfig = configure network interface parameters .
gateway route = router : ip route |grep default
trace route = prints the route that the packet takes to network host . destination host or IP is mandatory .
dig (domain information groper ) : innterogating DNS name server .
telnet :connects destinationhost port vis a telnet protocol if connection establishes then connectivity between the 2 host  working fine
nslookup :programe to query internet domain name server .
netstat :review each of network connection  and open sockets
scp :allows to secure copy file to and from another host in the network .
W :prints the summary of current activity , including what each is doing , and thier proceses also tells the logged in user and the system load average .
nmap : checks the opened port on the server .
enable or diable the network interface uses ifup/ifdown commands :
to enable say eth0 ,#ifup eth0 ; to disable  #ifdown eth0