The IT Stuff

A stub router is one that is connected to no more than two neighbors and should never be a transit router.The Enhanced Interior Gateway Routing Protocol (EIGRP) Stub Routing provides

improves network stability,
reduces resource utilization,
and simplifies stub router configuration.
The stub router has one exit path from the routing domain and forwards all traffic to a central [...]

There is a fundamental difference between Switch &  hubs functionality. When a hub receives a packet on one port, it will send out a copy of that packet on all ports except on the one where it was received. On the other hand Switch build up a Layer 2 forwarding table based upon the source [...]

VLAN Trunking Protocol (VTP) is a Cisco Layer 2 messaging protocol.
Manages the addition, deletion, and renaming of VLANs on a network-wide basis.
VTP reduces administration in a switched network.
When you configure a new VLAN on one VTP server, the VLAN is distributed through all switches in the domain. This reduces the need to configure the same [...]

To backup Active directory you back up the System State on Domain Controller  servers.
The System State contains

The local Registry,
COM+ Class Registration Database,
the System Boot Files,
certificates from Certificate Server (if it’s installed),
Cluster database (if it’s installed),
NTDS.DIT,
and the SYSVOL folder.

General Certifications: Three Levels of Certification

Associate: The first step in Cisco networking begins at the Associate level, which also includes CCENT, an interim step to Associates for those with little job experience. Think of the Associate level as the apprentice or foundation level of networking certification.
Professional. This is the advanced or journeyman level of certification.
Expert. [...]