finals

Star Topology

1. Every device is connected to a central switch or hub.

2. All data passes through the hub, making it a potential single point of failure.

Star Topology

Real-world example: Office with a centralized server room — if the main switch fails, all computers lose connectivity.

Mesh Topology

1. Devices are interconnected; data can take multiple paths.

   1. Can be full (every device connects to every other) or partial.

Mesh Topology

1. Example: Military communications where no single point can fail; the network reroutes if a node goes down.

1. Bus Topology

1. One backbone cable connects all devices.

2. Signals travel in both directions and are terminated at both ends to prevent reflection.

Bus Topology

1. Example: Legacy CCTV setups in small shops.

Ring Topology

1. Devices form a circular loop.

2. Data travels in one direction (or two in dual-ring).

Ring Topology

1. Example: FDDI (Fiber Distributed Data Interface) in industrial environments.

Hybrid Topology

1. Combination of any two or more topologies.

Hybrid Topology

1. Example: A campus with star topologies in each building connected in a ring.

Traffic Types

it consist of Unicast, Broadcast, and Multicast

Unicast

• One-to-one communication (e.g., computer A sends a file to computer B).

Broadcast

• One-to-all (e.g., ARP requests in IPv4).

Multicast

• One-to-group (e.g., video conference stream).

Star Topology

Traffic Behavior	Potential Issues
Central switch handles all traffic	Congestion at the switch

Mest Topology

Traffic Behavior	Potential Issues
Load is spread; backup routes	Redundant paths complicate routing

Bus Topologyq

Traffic Behavior	Potential Issues
All devices share the same line	Collisions, especially under heavy load

Ring Topology

Traffic Behavior	Potential Issues
Passes through each node	Delays if the ring is long

Hybrid Topology

Traffic Behavior	Potential Issues
Varies; combines behaviors	Complexity in management

star

Real-world traffic issue examples:

• In a ___ topology, a streaming video slows down for all users. Diagnosed as switch congestion due to high throughput demand.

bus

Real-world traffic issue examples:

• In ___ topology, a simple cable fault causes the entire network to stop working due to signal breakage.

Top-Down

1. Start at the application layer: Is the website accessible?

2. Then move downward: DNS → IP → network layer → physical.

Top-Down

1. Example: A browser can't open a site — check DNS resolution → ping → check network cable.

Bottom-Up

1. Start with physical hardware: cables, NICs.

2. Move upward to IP config, firewall, application settings.

Bottom-Up

1. Example: No connectivity — first check cable connection → lights on NIC → then IP address.

Divide and Conquer

1. Use tools like ping, tracert, nslookup to isolate where the connection fails.

Divide and Conquer

1. Example: Can ping router, but not internet — gateway issue.

IP Conflict

Two devices with same IP address. Causes erratic connectivity.

DNS Problems

• Can ping IP but not domain name? DNS not working.

Cable Break

• : Especially critical in bus/ring.

Loopback Configuration Error

• Common in mesh with dynamic routing.

MAC Flapping

• Seen when switches receive MAC addresses from different ports rapidly — sign of a loop.

Star

• Easy to diagnose: Check the switch → LEDs, port configs.

• PC can be swapped or cable changed quickly.

Mesh

• Redundant, but complex.

• If OSPF or EIGRP routing isn't configured correctly, some devices can't communicate.

• Example: A site with redundant links, but one misconfigured — packets loop endlessly.

Bus

• Signal stops flowing if backbone cable breaks.

• Terminators missing = signal bounce = network crash.

• Example: Legacy CCTV system fails after new junction added — terminator removed.

Ring

• Token-passing system.

• Token can be lost or duplicated.

• One node failure = ring is broken.

Hybrid

• Hardest to troubleshoot.

• Example: A school uses star in classrooms, connected via mesh. If a mesh router fails, only that building is affected.

Command Line

includes Ping, tracert/traceroute. ip config/ ifconfig, arp-a, netstat

ping

It test if host is reachable

tracert/traceroute

show path a packet takes

ip config/ifconfig

it check IP info

arp -a

it view MAC to IP mappings

netstat

It View active connections

GUI Tools

it includes Wireshark and SolarWinds/Nagios

Wireshart

Packet sniffer to view traffic and analyze anomalies.

SolarWinds/Nagios

• SNMP-based monitors Network monitoring (alerts on downtime, unusual bandwidth).

Star

• Easy to isolate compromised devices.

• Switch port security: Can lock ports to specific MACs.

Mesh

• Redundant paths can be exploited if routing isn’t secure.

• Threat: Route poisoning or man-in-the-middle attacks.

Bus

• Vulnerable to sniffing — anyone can listen to all traffic.

• Hard to enforce access control.

Ring

• Attackers can flood the ring or hijack token (if not encrypted).

Hybrid

• A weak part compromises the strong — a “chain is only as strong as its weakest link.”