Network Topology Is a way of Connecting Computers in the Network. and Every Design has its Own Feature. But here is Three main type of Topology.

1. BUS TOPOLOGY- 

ROUTER-

Twisted Pair Cable was invented by Graham Bell. As From Name anyone can Easily Understood
This is a type of Cable Which is Twisted on other Cable. But the question is why they are Twisted.
The Reason behind twisting is Cancelling out ,Electromagnetic Interference from External Sources
and Electromagnetic radiation from UTP (unshielded twisted pair cable ) cable.

• UNSHIELDED TWISTED PAIR

UTP Cable are used for Networking  and Traditional Telephone. There are Seven type of UTP Cable,

UTP CATEGORY	DATA RATE  (mb/s)	MAX-      LENGTH	CABLE-TYPE	APPLICATION
CAT 1	1	100m	Twisted pair	old-Telephone
CAT	4	100m	Twisted pair	Token Ring
CAT 3	10	100m	Twisted pair	Token Ring,10-base-T
CAT 4	16	100m	Twisted pair	Token Ring
CAT 5	1Gb/s	100m	Twisted pair	Token Ring, Ethernet,FE
CAT 5e	10Gb/s	100m	Twisted pair	Ethernet,FE,GbE
CAT 6	10Gb/s	100m	Twisted pair	GbE, 10-    GE(55m)
CAT 6a	10Gb/s	100m	Twisted pair	GbE, 10-    GE(55m)
CAT 7	10Gb/s	100m	Twisted pair	GbE, 10-    GE(100m

            

 NOTE- CAT 5e is most popularly used cable in all categories.

CCNA means Cisco Certified Network Associate is a Entry Level Certification for Network Engineers. some low level certificates are also available Like Cisco Certified Entry Networking Technician (CCENT) and  Cisco Certified Technicians (CCT). 
CCNA Routing and Switching are most common requirement for any other Associate level course. Some other course related to Associate level are as: 

CCDA

CCNA Cloud

CCNA Collaboration

CCNA CyberOps

CCNA Data Center

CCNA Industrial

CCNA Security

CCNA Service Provider

CCNA Wireless

This is the position that any CCNA certified candidate can get easily.

1. Network Engineers-
 The job responsibility of Network Engineers are to Maintain the Existing Network Performance. and Configuration of Routing and Switching Equipment. 

2. Network Administrator-
The person on this position are responsible for Installing Network and Computer Systems, Maintain and Upgrade Computer system.Knowledge of hardware and Software are also required .

3. Desktop Support Engineer-
This Position is quit easy. and anyone can get this job with little effort. But one important thing about this position is you must have good Communication skill. It may require some other language from your native language because you may provide support globally. You may also responsible for take backup of the data. 
                       
4 .Technical Support Engineer-
Technical Support Engineer are mostly provide support to the distance user on client end.  

   
               


                                 

Hub is a device that are used for same Collision domain.It is basically a center point in the LAN. It is also used in network as Repeater So It Repeat Electrical Signal that comes in one port out all other port. HUB are layer one device in OSI model  and not uses Ethernet frame or addressing. That's why they can't decide which port a signal should be sent . Hub send data through broadcast. Hubs are currently not used because It create unnecessary traffic in the network. And this work in half duplex mode and can easily captured by Network Sniffing.

                                     

In Half Duplex data can be send to only in one direction. So It can be Describe as If data is receiving on any node of the Network then at the same time You can not send data to any other Node. This type is called Half duplex. Some example that follow half duplex mode are HUB.(but currently hub are not in use or rarely used in Ethernet.) In half duplex mode only one cable are used for both send and receive data.

In full duplex mode any Node in the Network can receive and send Data at same instant. In Full Duplex mode two cables are separately used for send and receive the data.