CompTIA Network+ N10-008 Study Guide

Chapter 5 Common Network Connectivity Devices

Objectives

1.6 Explain the use and purpose of network services 2.1 Compare and contrast various devices, their features, and their appropriate placement on the network

Network Time Protocol (NTP)

Network Time Protocol is a way of synchronizing clocks across devices on a network. NTP is an important concept because it provides a mechanism for

Time Logging
Security Logs
Ensure sequencing of tasks
Ensure tasks are not delayed or running late

Network Interface Cards (NIC)s

Layer 2 device installed in your computer to connect, or interface, your computer to the network. It provides the physical, electrical, and electronic connections to the network media.

Hub

Hubs are layer 1 devices that broadcast transmissions to all hosts or nodes on the network. Usually used in a Star Topology

Bridge

A bridge is a Layer 2 device that connects two different networks segments together and breaks up the collision domain. Bridges are a software design not a hardware design.

Switch

Switches are Layer 2 devices which have intelligent port forwarding looking at the source and destination MAC Addresses. They can also provide Virtual LANs, Firewalls, break up collision domains using different hardware or software techniques. Switches basically just forward for filter frames. By default switches break up collision domains.

Switches will not segment a network packet that is targeted for broadcast or multicast

Multilayer Switch

A multilayer switch (MLS)

Routers

Routers are layer 3 devices that are more intelligent versions of bridges and are actual hardware instead of just software. Routes can provide port forwarding, firewalls, virtual LANs. They can also hold onto best network paths to traverse and forward packets.

Routers do not forward broadcasts by default
Routers can filter the network based on layer 3 information such as IP Addresses
Routers use logic addresses at layer 3 to understand the next hold
Routers can use access lists, created by an administrator, to control security on the types of packets that are allowed to enter or exit an interface
Routers provide Quality of Service (QoS) Services
Routers can provide layer 2 bridging functions if needed and can simultaneously route through the same interface.

Types of packets

Route Update Packets - Tell the router information about their neighbors, and what they know about their neighbors for forwarding packets
Data Packets - information that is ideally intended for a host connected to the router’s network

Functions

Packet switching
Packet filtering
Internet communication
Path Selection

Firewall

A firewall provides a way of filtering traffic between internal network devices or allowing or blocking outside traffic

IDS/IPS

Intrusion Detection System records traffic and alerts the appropriate systems or administrators when detected

Intrusion Prevention System Blocks the incoming threats

HIDS

Host Based Intrusion Detection System is software that is installed on a single computer and blocks malicious traffic

Access Point

Access points are the wireless form of a hub. They have no intelligent mechanisms to control the flow of traffic.

Wireless Range Extender

WLAN extends the signal using the same radio frequency as the source Access Point or Router and can be directly pointed at clients that are difficult to reach

Wireless LAN Controller

Wireless LAN Controller provides access for a single point to configure multiple remote routers connected to the network. It is used by Network Administrators to drastically reduce the time it takes to configure systems.

Load Balancer

A load balance uses an algorithm to forward traffic from one IP address to many other internal IP addresses as a way of keeping a large amount of traffic flowing and not overloading a single point on the network or system.

Contention Method

A contention method is when two or more devices are competing for a single resource and all packets are destroyed.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)

Wireless systems cannot detection collisions

How it Works

System sends out a signal to see if anyone is talking.
A random backoff algorithm is used by assigning a counter. Every time the system checks to see if the network is busy and doesn’t get to transmit, the system decrements it’s counter.
If a system detects no traffic at all it will transmit a message.
Frame is sent to the Access Point (AP).
Access Point sends an acknowledgment back to the system after the packet has been received. During the sending all other systems must remain silent.
When the frame’s turn comes up in the cache queue, the frame will be deployed to the destination system.
The destination/receiver of the data frame then will relay back to the Access Point with an Acknowledgement. during this time all other stations must wait before transmitting.

CSMA/CD

Carrier Sense Multiple Access with Collision Detection is easier to use on systems because it relies on physical hardware instead of radio waves for detecting collisions.

How it works

Check network wire for existing transmissions using Carrier Sense
If the wire is clear the device will transmit
If another device randomly starts transmitting both devices will detect the collision
Both devices will transmit a jam signal to all the other devices, which indicates to them to not transmit
The system will increment a special counter every time the system sends out a transmission on the wire and senses a collision. After a certain number of times the system aborts the frame.
A random backoff timer is set for all systems if a collection is detected before transmitting again.
Most cases a collision will not happen again because of the random backoff timer

Dynamic Host Configuration Protocol Server (DHCP) Server

DCHP Servers assign IP (Internet Protocol) Addresses to connected systems. It’s a way of assigning IP Addresses as systems connect to a network rather than assigning static IP addresses to a system
DHCP is an Application layer protocol that uses DORA (Discover, Request, Offer, Acknowledgement) at layer 2 (Data Link Layer)
Scope is a way of defining a range/pool of addresses within a subnet to reduce collision domains and assign IP Addresses from a DHCP Server.
An IP Address can be assigned to a system with a Lease Time-a time in which the host system is given an IP address but must release it after such they must request the same IP address or a new one.
One root domain starting with the “.” (period) character.
Common sub domains
- .com - typically assigned to for-profit companies
- .edu - assigned to education organizations
- .gov - assigned to local or federal government websites
- .int - assigned to international organizations such as NATO
- .mil - strictly for military
- .net - a network organization such as your ISP
- .org - assigned to a nonprofit organizations
DHCP Relay is if a message for a IP Address is relayed to another DHCP Server that may be on a different network and then forwarded back to the host system requesting one.

Domain Name Server (DNS)

reverse lookup is a way for finding a hostname based on the IP (internet protocol) address
DMZ is an internal DNS server which provides lookups

Record Types

A Record - an alias record that converts human readable characters or text into an IPv4 address
AAAA Record - an alias record that converts human readable characters or text into an IPV6 address
TXT Record - is a record which typically can be used to store any data but is often a way to confirm ownership of a domain
PTR Record - is an alias record which sends an IP address or host name to another domains
MX Record - is for mail exchange Servers
SRV Record - is for a Service record that is stood up typically inside of an organization’s intranet
CNAME Record - is commonly used to alias one record for another such as www.example.com to example.com
NS Records - strictly belong to Authoritative DNS Servers for a Domain

Proxy Server

A proxy server is a type of server that handles its client-machine requests by forwarding them on to other servers while allowing granular control over the traffic between the local LAN and the Internet. Proxy servers act at the Application Layer (Layer 7) of the OSI Model.
web proxy server is usually used to create a web cache.
caching proxy server is usually a caching proxy server speeds up the networks service requests by recovering information from a client’s earlier requests.

Encryption Appliances

An encryption appliance can sit in the middle of two connected lines and encrypt or decrypt information as it is sent along the physical medium

Analog Modem

Analog Modems are device which convert phone signal into usable bytes to a computer network, at layer 1

Packet Shaping

Packet Shaping is created by a device that can rate limit the amount of traffic come into a house or company so it doesn’t flood the network

Media Converter

Media converter is a device which can be used to convert the physical signals of transmitted on a network from one medium to another such as fiber to analog or copper wire signaling.

IPAM (Internet Protocol Address Management)

IPAM Software more easily allows for tracking IP Addresses which are used and assigned to Hosts.

Creating a Network

Deciding factors for choosing equipment

Growth of the network. How fast does the network need to be able to scale
Available cost. What is the initial cost for the scope of the work, how much needs to be allocated for the future?
Security. What compliances if any do you need to maintain or security concerns need to be mitigated
Maintainability - How easy to troubleshoot the network matters

Causes for Network Congestion

Multicasting
Lowe Bandwidth
Adding hubs for connectivity to the network
Broadcast storms
Too many hosts in a broadcast domain

Exam Essentials

Understand how DHCP (Dynamic Host Configuration Protocol) works and it’s purpose
Understand how DNS (Domain Name System) Server works and it’s purpose
Understand the difference between a hub, a switch (bridge), and a router
Remember the different names for a router
Remember the various devices used on networks today, and when you would use each one, and how
Identify the purpose, benefits, and characteristics of using a proxy service
Describe the proper use of network segmentation when planning and implementing a basic Small Home, Small Office Network- Describe the benefits of using a network load Balancer
Describe the benefits of using dedicated appliances for certain services

Written Lab Questions

Description	Device or OSI Layer
This device sends and receives information about the network layer
This layer creates a virtual circuit before transmitting between end stations
A layer 3 switch or multiplayer switch
This device uses hardware addresses to filter a network
Ethernet is defined at these layers
This layer supports flow control and sequencing
This device can measure the distance to a remote network
Logical Addressing is used at this Layer
Hardware addresses are defined at this layer
This device creates one big collision domain and one large broadcast domain
This device creates many smaller collision domains, but the network is still one larger broadcast domain
This device can never run full duplex
This device breaks up collision domains and broadcast domains

Review Questions

Which of the following is not a term used when making SOHO Internet connections?
- A. Hub
- B. Router
- C. NIC
- D. Switch
- E. IDS/IPS
What advantage does a switch have over a hub
- A. It discards frames
- B. Transmissions received on one port will be sent out all the other ports
- C. It recognized frames boundaries and destinations MAC addresses of incoming frames
- D. Any two or more devices that switch connects are capable of causing a collision with each other
Which device is used to segment a network?
- A. Hub
- B. Switch
- C. Repeater
- D. All of the above
What is the primary function of a bridge?
- A. Breaks up collision domains
- B. Allows a NIC or other networking device to connect to a different type of media than it was designed for
- C. Allows mobile users to connect to a wired network wirelessly
- D. None of the above
A network device that is used to connect multiple devices together without segmenting a network is a __
- A. Hub
- B. Wireless access point
- C. Switch
- D. Router
Which of the following is among the benefits of a switch?
- A. Protect LAN Resources from attackers on the internet
- B. Provides extra bandwidth
- C. Reduces throughput
- D. Allows access to all computers on the LAN
Which of the following devices can work at both layers 2 and 3 of the OSI model?
- A. Hub
- B. Switch
- C. Multilayer switch
- D. Bridge
What is an advantage of using DHCP in a network environment?
- A. More difficult administration of the network
- B. Static IP addressing
- C. Can send an operating system for the PC to boot from
- D. Assigns IP Addresses to hosts
What is a benefit of multilayer switch (MLS) over a layer 2 switch?
- A. Less Bandwidth
- B. Routing functions
- C. Fewer features
- D. Fewer ports
Which device should be used if you need to send incoming packets to on or more machines that are hidden behind a single IP address?
- A. Switch
- B. Load balancer
- C. Hub
- D. Repeater
What role does the A record in a Domain NAme Service (DNS) server have in your network?
- A. Translate human name to IP address
- B. Translates IP address to human name
- C. Enables printing, copying, and faxing from one device
- D. Controls network packets to optimize performance
Which device does not aid in network segmentation?
- A. Router
- B. Switch
- C. Hub
- D. Bridge
What is the most common use for a web proxy?
- A. Web cache
- B. Throughput increase
- C. DHCP services
- D. Support for the user authentication
Which is not an advantage of network segmentation?
- A. Reducing congestion
- B. Improving security
- C. Containing network problems
- D. Preventing broadcast storms
Users arrive at the office after a weekend and the hosts that were shutdown over the weekend are restarted but cannot access the LAN or internet. Hosts that were not shut down are working fine. Where can the problem be?
- A. The DNS server
- B. The DHCP server
- C. The proxy server
- D. The Firewall
You need a device that can prevent your users from accessing certain websites. Which device should you install?
- A. Firewall
- B. IDS
- C. IPS
- D. Proxy server
Which device creates separate collision domains and a single broadcast domain?
- A. Hub
- B. Router
- C. Switch
- D. Modem
Which of the following is not an advantage of using appliances to offload services like encryption and content filtering?
- A. Less Expensive
- B. Reduced load on other devices
- C. Additional functionality
- D. Better performance
Which type of server in your network uses pointer and A records?
- A. NAT translation server
- B. IDS/IPS server
- C. DNS server
- D. Proxy server
Users on your network are saturating your bandwidth because they are using too many non work related sites. What device would limit the availability of the types of sites that users on a LAN have access to while providing granular control over the traffic between the local LAN and the internet?
- A. Switch
- B. DHCP server
- C. DNS server
- D. Proxy server

Written Lab Answers

Description	Device or OSI Layer
This device sends and receives information about the network layer	Router
This layer creates a virtual circuit before transmitting between end stations	Transport
A layer 3 switch or multiplayer switch	Router
This device uses hardware addresses to filter a network	Bridge or Switch
Ethernet is defined at these layers	Data Link and Physical
This layer supports flow control and sequencing	Transport
This device can measure the distance to a remote network	Router
Logical Addressing is used at this Layer	Network
Hardware addresses are defined at this layer	Data Link (MAC sublayer)
This device creates one big collision domain and one large broadcast domain	Hub
This device creates many smaller collision domains, but the network is still one larger broadcast domain	Switch or bridge
This device can never run full duplex	Hub
This device breaks up collision domains and broadcast domains	Router