Chapter 2 - Concepts, Characteristics of Networking Flashcards
Network Traffic Types?
Broadcast Domain
Collision Domain
Broads Cast Domain?
Consists of all devices receiving a broadcast packet which can originate from any device.
Large # of broadcast last can reduce network bandwidth.
Can effect processing power as the broadcast is heated by every system in the broadcast domain.
Any device stops processing to listen to the broadcast to accept or discard the packet.
A router indicates boundary limit as they discard brackets
Collision Domain
Network segment where a collision can occur.
Typically Ethernet networks.
Consists of devices connected to a shared media.
If hubs are used they operate they operate at the physical layer, are not aware of addressing and broadcast data across all ports.
A switch operating and the data link layer which is swear of addressing and stops collisions occurring. It uses the MAC address to send data to the receiver only.
CSMA/CD
Carrier Sense Multiple Access/Collision Detection
Better manages and detects collisions.
Determine how network devices respond when simultaneous requests are made on the same data channel.
Attempts to re send transmission after a time interval to help reduce collision chance.
CSMA/CA
Detects and avoids collisions on a network.
Listens for collisions prior to transmitting data and informs other devices not to broadcast.
Send dummy packet for collision check.
Segmentation
Keeps traffics isolated using segmentation
Virtual LAN
Use a switch to isolate systems on a network from each other.
If needed devices and communicate between VLANS.
Trunking
Used when needing more than one switch.
It builds a logical connection between two VLANS and allows systems on different sides of switches to be in the same VLAN.
Tagging Ports
Defined by IEEE 802.1Q
Used when multiple VLANS exist per port
Directs traffic to the appropriate VLAN
Not needed if only one switch.
Port Mirroring
Configure switch ports to mirror traffic between ports.
Captures traffic between devices while mirroring
only frames containing SIP/PID
MAC Address Table
Dynamically built on the switch using MAC address of frames it receives.
Can determine port forwarding
Address Resolution Protocol (ARP) Table
Maps IP Addresses to MAC Address.
Maintains a record of MAC and corresponding IP Addresses
Can implement a switching loop
Switching loop
Sends a request to other switches if the current switch doesn’t have a MAC address in the ARP Table or is missing the address.
Spanning Tree Protocol can detect a switching loop and stop it if the switch can’t find a correct MAC address.
DMZ
De Militarised Zone
Uses a firewall which only allows ports to be open to communicate with appropriate system types.
Protects internal systems in the network. Only systems needing to be exposed to the internet are.
Hub
Physical layer device
Connects systems within a LAN or different segments.
It broads casts arriving data across all ports
No swear of addressing
Switch
Network device that filters and forwards packets between LAN segments and hosts.
Operated in the Data Link Layer
Is swear of addressing and only sends data to the receiving device
Isolated network segments using device MAC Addresses
Router
Network device that forwards packets between networks.
Operates at the networking layer
Routing protocols
Enable routers to communicate with each other with respect to the routes they Handel.
RIP
Routing Information Protocol
A distance vector protocol
Shares routing information among other networks.
- Routers maintain a routing table which lists all destinations and is shared to other routers*
- Distance Vector algorithms determine which path is best to destination.*
Is open source
RIP considers how many routers have to be crosses to the destination via best path
EIGRP
Enchanted Interior Gateway Routing Protocol (EIGRP)
Enables routers to exchange information more efficiently and maintain a copy of neighbouring routing tables.
- RIP 2 only sends changes to updates of the routing table*
- RIP doesn’t take into account the state of the fastest path*
Links State Routing Protocol
Open Shortest Path First (OSPF)
A routing protocol used to determine the best path for packets.
Replaces RIP
As a router learns of a network change it will multi cast the information to all other OSPF hosts on the network.
- this updated neighbouring routing tables*
- also takes into account the state of chosen path. If path is busy it might choose a longer route that’s the most open path.*
Boarder Gateway Protocol (BGP)
Manages how packets are routed across the internet
Connects autonomous systems
Combines distance and reach ability and queries if routers are functioning along selected path
IPv6
Default IP since vista
128bit
Implemented due IPv4 address shortage.
Supports auto config which helps correct and limitations of IPv4
Converts hexadecimal to binary
16bits of 8bites
1 to 9 for digits and A to F for letters
2001:0CD8:BC20:ED02:0000:0000:0000:0000
Condensed to
2001:CD8:BC20:ED02::
Dual stack
Enables IPv4 and IPv6 to be used at the same time.
Both 4 and 6 are enabled by default
IPv6 is fine tuned to address common communication types like VOIP and Video conferencing
IPv6 Router Advertisement
Allowing client systems to recognise that a router is present
*IPv4 required anDHCO to inform client of its IP Address, subnet and default gateway.
IPv6 Neiboure Discovery
Performs tasks like
Router discovery
Duplicates address detection
Prefix discovery
Tasteless address auto config
Traffic/Packet Shaping
Regulates network data transfers
Ensures a level of performance and QoS
Prioritises traffic and delays packets deemed less important
Priority examples
VOIP
Time sensitive data like email over printing
Buisness related traffic
Internet service provider
Tiered internet like regular and standard
QoS
Quality of Service
Measures overall network performance, transmission and error rates.
Can improve traffic shaping like packet prioritisation,
Queuing, Application classification
DiffServ
Differential Services Protocol
Specified and controls network traffic by class
Based on class traffic can get precedence like VOIP as it requires an uninterrupted data flow.
DiffServ is dependant on compels policy and rules statements when forwarding network packets.
*Avoids simple priority tagging as it can be time consuming and take up resources tagging each packet.
CoS
Class of Service
Groups similar traffic types on a network to manage traffic like Email Video Voice File transfer like large documents
CoS doesn’t guarantee a level of service, only a best effort in terms of Bandwidth and Delivery Time
Main CoS Technilogies
1/ 802.1p for data link layer tagging
2/ Type of Service (TOS)
3/ Differentiated Service (DiffServ)
CoS focuses on maintaining best communication possible based on the communication type*
NAT
Network Address Translation
Used by network devices to assign a public address to a device within a private network.
- limits the number of public IPs used by a company*
- A private address is only visible to devices on the inside of the router on the private network*
- only 1 private address needed to get everyone into the internet*
NAT enables packets to be sent to a private address. As packet arrives at the router from inside the network it inserts a public address which is visible to a web server and knows which machine in the private network the data is for.
NAT Advantages
Prevents depletion of IPv4 addresses
Provide additional layer of security as private addresses can’t be seen from the public network.
Increase flexibility connecting to public internet
Use private IPv4 addressing system
NAT disadvantages
Consumers processor and memory resources
Can cause IPv4 communication delays
Loss of end device IP trace ability
Not comparable with some technologies or network applications
Needs to support NAT!
PAT
Port Address Forwarding
Is a NAT extension
Enables multiple network devices to be mapped to a single IP address.
Can configure a router or switch to forward data via port #
IP address example from public to a device on a private network
(public) . (private)
129. 1.2.3:1001
- you state a particular port number to get to a particular system*
- more robust routers support more port forwarding rules and are better at maintaining track of connections*
- NAT/PAT allow easier access from and to private and public networks*
PAT Advantages
Conserve IP addresses
Private IP addresses aren’t exposed to public networks
Limits attack origination from public network. As they don’t know the IP so can’t launch targeted attacks
PAT Disadvantages
More complicated in larger networks. Particularly with remote logins
Limited internal table in devices which may run out of unused ports or loose track of connections
Port Forwarding
Makes a network device accessible to other devices on the internet even when behind a router.
External connections go to the gateway and then to the port # of a requested service. The gateway will then forward the request to the relevant service via its port #.
Eg HTTP will use port 80 and data for port 80 is automatically forwarded to the private IP address inside the network.
you don’t have to manually state the uses port. Apps normally use default ports to get data to the correct service
Common use of port forwarding
Online gaming services
Peer to peer downloading
VOIP apps like Skype, Viber, ooVoo, Zoom
Do SOHO router support port forwarding?
Yes
You can run internet services from within a SOHO network such as
FTP
Email Server
Web Server
Limited number of about 10
ACL Koko
Access Control List
Determine who and what can use a particular network resource
- Router ms and some switches use ACL to restrict data flow to and from and network interface*
- Network interfaces are configured to use ACLs to analyse data as it arrives at the Router/Switch*
- once data arrives it is compared to the ACL criteria where it’s either denied or permitted*
- An external router can provide access to outside network connections*
When to use an ACL
1/ To enable basic security for a network. Not a firewall replacement but they can enable protection for network interfaces.
2/ Restrict Updates for Routing from network peers where you can set routers to accept updates from specific routers.
3/ helps to define flow control of network traffic.
4/ Can place ACL rules on external routers to filter traffic from less desirable networks and vulnerable protocols.
5/ To create a DMZ which is a buffer zone between the internal company network and external WAN (internet)
DMZ
De Militarised Zone
A buffer zone to protect internal network.
Only devices that require the internet reside in the DMZ. Like a Web server on DNS server.
Can set up a proxy server which devices go through and use to get internet connection
An external router is set up with a fire wall. The external router normally has less restrictive ACL to allow access.
And internal router and fire wall are set with more restrictive ACL to protect the internal network. Commonly configured as explicit allow or deny statements.
ACL along with Firewalls can increase network security
Public IP Addresses
Assigned by an internet service provider to be used by a home or buisness.
It differentiates devices connected to the public internet.
- must be globally unique*
- To access the internet you only need one public address.*
Private IP Addresses
Provides internal communication within a private network.
- Alleviates IPv4 IP Address exhaustion*
- All systems inside your router on the private network can use any IP address configuration*
- Configuration can be based on size for example*
IANA
Internet Assigned Numbers Authority
Reserves certain IP Addresses for private use.
Everyone can use these addresses in a private network!
Network classes.
A for large networks
B for medium networks
C for small networks
Class A network range
10.0.0.0 to 10.255.255.255
Class B Network range
172.16.0.0 to 172.31.255.255
Class C network range
192.169.0.0 to 192.168.255.255
APIPA
Automatic Private IP Addressing
A range of private IP addresses allowing devices to communicate if a DHCP server fails.
- implemented if use of a DHCP server. If a device can’t communicate with the DHCP an APIPA is assigned to allow internal communications to continue.*
- If you see an IP address starting with 169.254 you know there might be an issue with the DHCP server*
APIPA Address Range
169.254.0.0 to 169.254.254.255
Loop back Address mi
TCP/IPv4
Is a special address designed for the loop back interface of a machine
Packets for the loop back address is used for testing IP software has correctly configured TCP/IP.
- not concerned with corrupt drivers or hardware*
- ping command can be used to allow a user to perform a test on the loop back address. If you ping 127.0.0.1 and you get a reply it indicates TCP/IP is configured correctly on the machine*
- Ping 127.0.0.1 when facing issues with communication*
Loop back address range
Always set as 127.0.0.1
Range cane be
127.0.0.0 to 127.255.255.255
Reserved addresses
Private Addresses
Loop back Addresses
APIPA are reserved for Self assignment of a DHCP server goes off line
Addresses that can be used for diagnostics
APIPA - indicates issue with DHCP if IP address starts with 169.254
Loop Back Address 127.0.0.1 used to check a machines TCP/IP is correctly configured if you get a response
Default Gateway
Allows computers on a network to access the internet
- without a gateway devices are isolated from the internet*
- Not required to communicate within your private network*
- Computer with 2 network adapters can act as a gateway. 1 adapter connects to the subnet and the other connects to the public network (internet)
Common Default Gateway IP Addresses
- 168.0.1
- 168.1.1
- 168.0.254
- 0.0.1
Commonly use the 1st address (# 1) or last address (# 255) of a given subnet.
Subnet Mask
Used to determine what subnet an IP Address belongs to.
What does an IP Address consist of?
1/ Network Address that identifies the network
2/ Host Address which is a specific network host.
IP Address breakdown Class A
255.0.0.0
255 = Network and 0.0.0 = Host
IP Address breakdown Class B
- 255.0.0
255. 255 = Network and 0.0 = Host
IP Address Breakdown Class C
- 255.255.0
255. 255.255 = Network and .0 = Host
VIP
Virtual IP Address
Is an address that doesn’t correspond to a specific or physical network interface.
Same VIP is used and routed to a server
VIP Common Uses
Servers in a cluster. Which is a group of servers performing the same task.
Load balanced servers. Which share performance loads.
- Client only needs a single IP Address to access the server cluster, to direct requests to a health server*
- each server has its own IP Address*
VIP Benefits
Consolidate resources (Load Balancing)
Improve Redundancy (Cluster)
Virtually unlimited mobility without changing address. (can move the application to another server using Th we same VIP)
Shields device led actual IP Address.
Address Assignments
DHCP is a client/server protocol that automatically assigns a client with an IP, Subnet and gateway addresses.
Allocates from a pool of available IP Addresses.
- can be manually or dynamically assigned*
- lease for a time period*
DHCP Benefits
Reliable IP Address configuration
Minimises configuration errors like Typos and duplication conflicts.
Centrally managed and automated
No need too keep assigned IP address records.
How does DHCP assign a IP Address?
Uses DORA
Discover - packet send by client to ask for an address.
Offer - Sent by Server with addresses
Request - Sent by client to request one of the addresses
Acknowledge - sent by server acknowledging the requested IP address.
Static IP Addressing
Manually assigned to a device as opposed to DHCP
this IP Address doesn’t change and remains static
Static IP Common use
DNS Server
Network printer
Website
you don’t want these addresses to change
Static Addressing Advantages
Stability
Preferred addresses for servers
Remote Access forwarding
Reduced down time if DHCP server goes down.
Static addressing disadvantages
Security as addresses don’t change
Manual configuration open to duplication
Additional DHCP server configuration to ensure DHCP pool doesn’t include the static IP Addresses.
DHCP Reservations
Permanent address assignment within a scope
Is the alternative to static addressing to unequally identify device on a network.
A typical reservation includes
Reservation time
IP Address
MAC Address
Description
