http://www.joshgentry.com/cisco/cisco.htm
http://www.swcp.com/~jgentry/topo/cisco.htm
Network Calculators
http://www.subnetmask.info/
Classful IP Subnet Calculations
http://www.joshgentry.com/networking/subnet.htm
VPN Setup for Routers - Getting it to work with an IPSec Client
http://www.homenethelp.com/vpn/router-config.asp
http://www.javvin.com/protocol/
รวมเน็ตเวิร์ค
http://www.cs.virginia.edu/~cs458/slides/
http://www.cs.cmu.edu/afs/cs.cmu.edu/academic/class/15213-f98/lectures/
http://www.interlab.ait.ac.th/tein2/
http://www.ing-steen.se/utbildning/tcpip/tcpip.html
http://www.cs.wisc.edu/~suman/courses/640/lectures/
http://www.ittc.ku.edu/EECS/EECS_663/LOCAL/EECS_663_Class_Notes/
http://www.it.lut.fi/kurssit/05-06/index_fin.html
http://www.netcraftsmen.net/welcher/
http://www.soi.wide.ad.jp/class/20040013/