CCNA 200-301 Flashcards
What is a client, how is it different from a server?
A client is a device (or software) that accesses a service made available by a server.
It makes a request to the server (e.g., browsing a website, accessing a file, or querying a database).
A server is a device (or software) that provides services or resources to clients.
- It fulfills the request (e.g., sending a webpage, serving files, or processing a query).
- Can be hardware (physical server) or software (e.g., a web server like Apache).
Switch = Same LAN
What is a Switch?
Switches are network devices that forward traffic between networks in the same Local Area Network (LAN).
- Operates at Layer 2 (Data Link Layer) of the OSI model.
- Uses MAC addresses to forward data to the correct device within the LAN.
Router = Route between LANs
What is a Router?
Routers connect multiple networks, including different LANs and WANs.
- Operates at Layer 3 (Network Layer) of the OSI model.
- Uses IP addresses to determine the best path for forwarding packets between networks.
How does Firewalls work?
Firewalls monitor and filter network traffic based on rules to protect networks and devices.
Firewalls can filter traffic before it reaches the router (e.g., ISP firewall).
or filter traffic after passing through the router, typically at the network boundary.
What are the 2 types of firewalls?
Network firewalls are Hardware-based devices placed at the boundary of a network. Filters traffic between networks (e.g., between a LAN and the internet).
Host-based firewalls are Software applications running on individual devices (e.g., PCs, servers).
Filters traffic entering or leaving the host.
“All People Seem To Need Dominoes Pizza”
What are the OSI Layers?
- Application
- Presentation
- Session
- Transport
- Network
- Data Link
- Physical
What happens at the Application Layer?
Closest layer to the user. Protocols include HTTP/HTTPS/DNS - raw application information is sent toPresentation Layer.
What happens at the Presentation Layer?
Raw Data is formatted (ASCII to Unicode) encrypted (SSL/TLS) or compressed before passing to the Session Layer.
What happens at the Session Layer?
Establishes, manages, and terminates communication sessions. Adds session management info and passes to Transport Layer.
What happens at the Transport Layer?
Data is broken into Segments (Raw data + L4 TCP/UDP Header) and ensures reliable delivery (e.g., TCP/UDP). Segmented data is sent to the Network Layer.
What happens at the Network Layer?
Adds IP headers to segmented data - now a packet
Router forwards packets using routing tables. ARP resolves IP address to MAC addresses for local delivery. Packet is passed to the Data Link Layer.
What happens at the Data Link Layer?
Packet now has L3 header (MAC address) added and becomes a frame
Switches forward frames within LAN using MAC address tables. Frame is sent to the Physical Layer.
What happens at the Physical Layer?
Converts frames into signals (e.g., electrical signals via wires or Wi-Fi). Data is transmitted as bits over physical media (e.g., cables or wireless signals).
What is the Process if PC1 wants to send a frame to PC2? - how does it work?
What OSI layer and device is used?
Switch → S for Second-level (Layer 2- Data-link layer)
PC1 Sends Frame:
- Includes Destination MAC, Source MAC, EtherType, and Data.
Switch Receives Frame:
- Switch looks at the Destination MAC.
MAC Address Table:
- Switch stores Source MAC with port info in its table.
Forwarding the Frame:
- If Destination MAC is in the table, the switch sends the frame to the correct port.
- If not, it floods the frame to all ports except the one it came from.
PC2 Receives Frame:
- PC2 accepts the frame if Destination MAC matches its own.
Switch Updates MAC Table:
- Switch adds Source MAC and port to the table for future reference.
What is the Process if PC1 wants to send a frame to PC2? - but it doesnt know its MAC address
PC1 Needs PC2’s MAC Address
- PC1 knows PC2’s IP, but needs its MAC address.
ARP Request
- PC1 broadcasts an ARP request to find PC2’s MAC address.
ARP Reply
- PC2 responds with its MAC address.
PC1 Updates ARP Cache
- PC1 stores PC2’s MAC address in its ARP cache.
PC1 Sends Frame
- PC1 sends the frame to PC2 now that it knows PC2’s MAC address.
Switch Forwards Frame
- Switch forwards the frame based on PC2’s MAC address in its table.
Summary
- ARP resolves IP to MAC addresses, allowing PC1 to send a frame and the switch to forward it.
List the layers of OSI - include devices, PDU and protocols
-
Application Layer
- Devices: End-user devices (PCs, Servers)
- PDU: Data
- Protocols: HTTP, HTTPS FTP, DNS
-
Presentation Layer
- Devices: Gateways, Proxies
- PDU: Data (Translation, Encryption, Compression)
- Protocols: SSL/TLS, JPEG
-
Session Layer
- Devices: Gateways, Proxies
- PDU: Data (Session management)
- Protocols: NetBIOS, SMB
-
Transport Layer
- Devices: Gateways, Firewalls
- PDU: Segments (TCP) / Datagrams (UDP)
- Protocols: TCP, UDP
-
Network Layer
- Devices: Routers
- PDU: Packets
- Protocols: IP, ICMP
-
Data Link Layer
- Devices: Switches, NICs
- PDU: Frames
- Protocols: Ethernet, ARP
-
Physical Layer
- Devices: Hubs, cables
- PDU: Bits
- Protocols: Ethernet, USB
What do Switches do, at what layer?
Switches are Data Link Layer (Layer 2) devices.
- Forwarding Frames: Use MAC addresses to forward frames to the correct port.
- Learning MAC addresses: When a switch receives a frame, it records the Source MAC address and the port on which the frame was received, adding it to the MAC address table.
- Filtering Traffic: Forward frames to only the correct port, reducing unnecessary network load.
What do Routers do, at what layer?
Routers are Network Layer (Layer 3) devices.
- Forwarding Packets: Routers forward packets between networks based on IP addresses.
- Routing: Routers use routing tables and algorithms to determine the best path for data.
- Network Address Translation (NAT): Routers can perform NAT, which translates private IP addresses into public IP addresses when sending packets to external networks (e.g., the internet). This allows multiple devices in a local network to share a single public IP address.
- Traffic Management: Routers can apply Quality of Service (QoS) to prioritize traffic, ensuring that important data, like voice or video, gets higher priority over other types of traffic.
