Sudo : The basics

Basic structure of ACL entries for the sudoers file
Always use visudo to edit as it does syntax checking for you

Command aliases:
 Cmnd_Alias DIAGS = /usr/sbin/tcpdump,/usr/sbin/ethtool

Network / host aliases:
Host_Alias LAN = 192.168.0.0/255.255.255.0

You can then allow a user to access these commands:

This will allow Paul to run tcpdump & ethtool from anywhere without reentering his password:
paul    ALL = NOPASSWD:DIAGS

Or you can restrict it to certain subnets:
paul    LAN = NOPASSWD:DIAGS

Omit the NOPASSWD parameter if you want Paul to reenter his password everytime he uses sudo.

If you want paul to be able to become root and do anything:
paul    ALL=(ALL)     NOPASSWD:ALL