Notes: Intro to LAN | Pre Security | THM

Introducing LAN Topologies

Local Area Network (LAN)

Topology - design/look of the network at hand

Star Topology

- devices individually connected via a central networking device (switch/hub)

- reliable

- scalable (easy to add more devices) -> require more mentenance = troubleshooting faults harder

- prone to failure if the centralized hardware the devices connect to fails

- more cabling

- more expensive

Bus Topology

- a single connection (backbone cable) that each single device connects to

- traffic on same cable = slow/bottleneck if several devices request data

- difficult troubleshooting -> identifying which device is experiencing issue

- cost-efficient

- poor redundancy if failure along backbone cable

Ring Topology (Token Topology)

- devices connected directly in a loop

- little cabling

- data sent around loop in one direction until it reaches destined device

- devices prioritize to send its own data before the received data going through

- easy to troubleshoot as traffic only goes in one direction

- unefficient data traffic - may have to visit multiple before it reaches it destination device

- less prone to bottleneck as large data traffic are not being sent across at the same time

- poor redundancy if failure along the loop (entire network breaking if failure in loopcable)

Switch

- dedicated device

- designed to aggregate multiple other devices like computers, printers and other network-capable device using ethernet <- plut into a switch's port

- a switch can have ports of 4, 8, 16, 24, 32, 64

- switches more efficient than hubs/repeaters

- a switch knows what device is connected to which port = sends directly to correct device = reduced network traffic

- switches and routers can be connected to one another = increase redundancy/reliability <- multiple paths for traffic = no downtime

Router

- connect networks and pass data between them through routing

Routing

- creating a path between networks

- useful when several paths

A Primer on Subnetting

Subnetting

- term given to splitting up a network into smaller, miniature networks within itself (like slicing up a cake making sure everyone gets a piece)

- used to categorise and assign specific parts of a network to certain departments

- achieved by splitting up number of hosts to fit in the network = subnet mask

Subnet mask

- four bytes (32 bits), ranging 0-255

- use IP addresses in 3 different ways

1. Identify network address (start of network, example: 192.168.1.0)

2. Identify host address (device on subnet, example: 192.168.1.100)

3. Identify default gateway (special adr assigned a device capable of sending info to another network, example: 192.168.1.254)

- home network: one subnet (max 254 devices connected at same time)

- benfits of subnetting:

- efficiency

- security

- full control

ARP

Address Resolution Protocol (ARP)

- allowing devices to identify themselves on network = associate its MAC address with an IP address on the network

- each device on a network keeps log of MAC adr of other devices

- device wish to communicate -> broadcast to entire network searching for specific device - can use ARP for this

How ARP works:

- each device in a network has a (ARP) cache to store information (identifiers of other devices on the network)

- to map the 2 identifiers together (MAC and IP), ARP sends 2 types of msg:

1. ARP Request (broadcast on network: "What is the MAC that owns this IP?")

2. ARP Reply (only device that own IP will send an ARP reply with its MAC)

DHCP

Dynamic Host Configuration Protocol (DHCP)

- used to automatically assign IP addresses

- when device connect to network without IP:

1. DHCP Discover: device sends a request, looking for a DHCP server

2. DHCP Offer: DHCP server replies with an IP adr

3. DHCP Request: device send confirm reply

4. DHCP Ack: DHCP server reply and device can start using IP