You are on page 1of 10


An Ethernet hub, active hub, network hub, repeater hub, multiport repeater,
or simply hub
The main work of Hub is to receive incoming data signals, amplify them in the
form of electrical signals and then send them to each connected device. A
Hub may contain a number of ports. Minimum amount of ports that a hub can
have is 4 and it can have up to 24 ports for connecting various devices and
peripherals to it.
1. When referring to a network, a hub is the most basic networking device
that connects multiple computers or other network devices together. Unlike a
network switch or router, a network hub has no routing tables or intelligence
on where to send information and broadcasts all network data across each
connection. Most hubs can detect basic network errors such as collisions, but
having all information broadcast to multiple ports can be a security risk and
cause bottlenecks.
2. In general, a hub refers to a hardware device that enables multiple devices
or connections to be connected to a computer. Another example besides the
one given above is a USB hub, which allows multiple USB devices to be
USB connections. The picture to the right is an example of a USB hub.
of the LAN can see all packets.

What Hubs Do
port of the destination PC.

Passive, Intelligent and Switching Hubs

additional features that enables an administrator to monitor the traffic
hubs are also called manageable hubs.

Types of Hub:On the basis of its working

methods, the Hubs can be divided into three
types, given as:
Active Hub: As its name suggests, Active Hub is a hub which can amplify or
regenerate the information signal. This type of bus has an advantage as it
also amplifies the incoming signal as well as forward it to multiple devices.
This Bus is also known as Multiport Repeater. It can upgrade the properties if
incoming signal before sending them to destination.
Passive Hub: Passive Hub works like a simple Bridge. It is used for just
creating a connection between various devices. It does not have the ability to
amplify or regenerate any incoming signal. It receives signal and then
forward it to multiple devices.
Intelligent Hub: This is the third and last type of Bus. It can perform tasks of
both Active and Passive buses. Also, it can perform some other tasks like
Bridging and routing. It increases the speed and effectiveness of total
network thus makes the performance of whole network fast and efficient.
Home and Small Business Hubs
Hubs can be used as a standalone device or connected to compatible hubs
and switches to form a larger network. Hubs are generally easy to install and
maintain, making these devices a good option for home networking. A hub is
also easily configured for small business branch office networking.
Physical layer function
A network hub is an unsophisticated device in comparison with a switch. As a
multiport repeater it works by repeating bits (symbols) received from one of
its ports to all other ports. It is aware of physical layer packets, that is it can
detect their start (preamble), an idle line (interpacket gap) and sense a
collision which it also propagates by sending a jam signal. A hub cannot
further examine or manage any of the traffic that comes through it: any
packet entering any port is rebroadcast on all other ports.[3] A hub/repeater

has no memory to store any data in a packet must be transmitted while it is

received or is lost when a collision occurs (the sender should detect this and
retry the transmission). Due to this, hubs can only run in half duplex mode.
Consequently, due to a larger collision domain, packet collisions are more
frequent in networks connected using hubs than in networks connected using
more sophisticated devices.
Some Application of Networking Hub are given below:
Hubs are used to create small Home Networks.
Hubs are used for monitoring the networks.
Hubs are used in Organizations and Computer Labs for connectivity.
It Makes one device or peripheral available throughout the whole network.
Hub is less expensive product.
It is used for connect the multiple devices.
a hub can be able to support multiple users at the same time
It will broadcast to all the ports
It runs half duplex
If 10 Ports in a hub it will share bandwidth of 100 MbPs.
So each port share 10 Mbps
.It is a non intelligent connection

data to the destination device.


A network switch is a multiport network bridge that uses hardware addresses

incorporating routing functionality that most commonly uses IP addresses to
Asynchronous Transfer Mode, and InfiniBand. The first Ethernet switch was
introduced by Kalpana in 1990.
Switches manage the flow of data across a network by transmitting a
maximizes the security and efficiency of the network.
Because broadcasts are still being forwarded to all connected devices, the
newly formed network segment continues to be a broadcast domain.
degrading the overall efficiency of the network.
The network switch plays an integral role in most modern Ethernet local area
and components that interface to the particular physical broadband
technology. User devices may also include a telephone interface for Voice
over IP (VoIP) protocol.


larger collision domain into smaller ones in order to reduce collision
the switch ports. This allows computers to have dedicated bandwidth on
receiver per "collision domain", making collisions impossible.
the entire network, limiting its overall capacity.



usually have a feature called port mirroring that provides the same

By the early 2000s, there was little price difference between a hub and a lowend switch.[12]

Layer 2[edit]
which the bridge learns the MAC address of each connected device.

Single bridges also can provide extremely high performance in specialized

applications such as storage area networks.

Classic bridges may also interconnect using a spanning tree protocol that
the spanning tree reconverged. A Rapid Spanning Tree Protocol was
802.1aq) is the next logical progression and incorporates all the older
the use of the mesh topologies through increase bandwidth and redundancy

use microsegmentation and full duplex to prevent collisions among devices
connected to Ethernet. By using an internal forwarding plane much faster
than any interface, they give the impression of simultaneous paths among

method were performance-increasing methods when used on "switch"
products with the same input and output port bandwidths:

Store and forward: the switch buffers and verifies each frame before
Cut through: the switch starts forwarding after the frame's destination


frame, where addressing information is stored. According to Ethernet
Adaptive switching: a method of automatically selecting between the other
three modes.
While there are specialized applications, such as storage area networks,
user access typically concentrates lower bandwidth and uplinks into a higher

Layer 3[edit]
device has signaled that it wants to listen to that group.

Layer 4[edit]
almost always starts with a capability for network address translation, but
then adds some type of load distribution based on TCP sessions.[18]


security gateway.

Layer 7[edit]

participate in a content delivery network (CDN).
Configuration options[edit]
Unmanaged switches these switches have no configuration interface or
Unmanaged switches can be desktop or rack mounted.
Managed switches these switches have one or more methods to modify the
operation of the switch. Common management methods include: a
Shell, an embedded Simple Network Management Protocol (SNMP) agent
allowing management from a remote console or management station, or a
web interface for management from a web browser. Examples of
configuration changes that one can do from a managed switch include:
enabling features such as Spanning Tree Protocol or port mirroring, setting
port bandwidth, creating or modifying virtual LANs (VLANs), etc. Two subclasses of managed switches are marketed today:
Smart (or intelligent) switches these are managed switches with a limited
VLANs, port-bandwidth and duplex.[20]
Enterprise managed (or fully managed) switches these have a full set of
may have additional features to manipulate configurations, such as the ability
switches, enterprise switches have more features that can be customized or
optimized, and are generally more expensive than smart switches. Enterprise
switches are typically found in networks with larger number of switches and
connections, where centralized management is a significant savings in
administrative time and effort. A stackable switch is a version of enterprisemanaged switch.
Advantages :
1) Reduces the number of Broadcast domains
2) Supports VLAN's which can help in Logical segmentation

of ports[physical ports].Splitting up the broadcast domain.

3) Intellegent device[compared to Hub's] which can make use
of CAM table for Port to MAC mapping
4) Compared to Bridges ,Switches are more H/w oriented
therefore operations are less CPU intense[Basic operations]
5) The cost to number of ports ratio is best .. ie For a
cheaper cost you get switches with more number of ports
available than Routers.

Disadvantages :

1) Not as good as a router in limiting Broadcasts

2) Communication b/w VLAN's need interVLAN routing [Router]
,but these days there are a number of Multilayer switches
available in the market.
3) Handling Multicast packets needs quite a bit of
configuration & proper designing.
4) At times swtiches when in Promiscuos mode is a opening
for Security attacks [Spoofing ip address or capturing
Ethernet Frames using ethereal]

I would definitely arguee with the interviewer that

switches are designed for what they are & there is
disadvatage as such unless it is compared to other layer
devices.At Layer 2 it does what other devices of layer 2

cant do & it was initally meant to work at Layer 2,even

though it works at multiple layers these days.


A router [a] is a networking device that forwards data packets between

through the networks that constitute the internetwork until it reaches its
destination node.