QoS Calculator

Source: http://www.netcontractor.pl/blog/wp-content/uploads/2010/06/QoS-Values-Calculator-v21.jpg

Fresnel Zone

Newbie

Area Border Router

OSPF advertisement Forwarding

OSPF Designated Router Affect

Multicast MAC address Construction

Source: http://www.a2znetworks.com/2011/02/multicast-part-2-multicast-addresses.html

QOS Values Calculator

Source: http://www.netcontractor.pl/blog/?tag=dscp

EIGRP

EIGRP Relationship Formation

EIGRP Distances

Amazing resource for EIGRP:
http://ciscodocuments.blogspot.ca/2011/05/chapter-02-configuring-enhanced.html

Using L2 Tunnel - ISP

Spanning Tree Again

http://www.cisco.com/image/gif/paws/10556/spanning_tree1.swf

Basic but well explained....

Multicast Again

Multicast communication is a one-to-many communication pattern. It can be viewed as a broadcast to a subset of nodes of the network

Source: http://upload.wikimedia.org/wikipedia/commons/7/7b/Multicast_forwarding.png