Cybersecurity Module 7

What are the criteria for dividing local networks?

Local networks can be divided based on:

1. Broadcast containment

2. Security requirements

3. Physical locations

4. Logical grouping

What is the role of the distribution layer in a network?

The distribution layer:

• Connects independent local networks.

• Controls traffic flow between networks.

• Keeps local traffic within the local network.

• Filters incoming and outgoing traffic for security and traffic management.

How do routers limit broadcast traffic in a network?

Routers in the distribution layer limit broadcast traffic to the local network, preventing excessive broadcast traffic that can slow down the network.

What is the process of routing?

Routing is identifying the best path to a destination. A router:

• Reads the Layer 3 IP address.

• Decapsulates the Ethernet frame.

• Encapsulates the packet into a new frame for forwarding to the destination network.

What is a routing table, and how is it updated?

A routing table contains:

• Addresses of networks.

• Best paths to those networks.

Entries can be:

• Dynamically updated from other routers.

• Manually entered by administrators.

What is a default route in a router’s routing table?

A default route is the interface used by a router to forward packets to unknown destination networks.

How does a default gateway work?

The default gateway is the router interface connected to a local network. It:

• Receives packets destined for remote networks.

• Uses ARP to determine its MAC address.

What are the characteristics of a Local Area Network (LAN)?

A LAN:

• Is under one administrative control.

• Uses Ethernet or wireless protocols.

• Supports high data rates.

What are the advantages of placing all hosts in one local segment?

1. Simpler network setup.

2. Lower cost.

3. Faster data transfer and direct communication.

4. Easy device access.

What are the disadvantages of placing all hosts in one local segment?

1. High traffic in one broadcast domain may slow performance.

2. Harder to implement QoS and security.

What happens when the network portion of the source and destination IP addresses do not match?

A router is used to forward the message to the destination network by:

1. Reading the destination IP address.

2. Determining the best path using the routing table.

3. Encapsulating the packet in a new frame for forwarding.

What is the difference between routers and switches in decision-making?

• Routers make forwarding decisions based on the Layer 3 IP address.

• Switches make forwarding decisions based on the Layer 2 MAC address.

How do routers obtain destination MAC addresses?

Routers use ARP tables to:

1. Store MAC and IPv4 addresses of connected hosts.

2. Determine the correct MAC address for forwarding packets.

What are the functions of a router interface?

• Acts as part of the local network to which it is attached.

• Maintains an ARP table for that local network.

• Forwards packets to the correct destination or to another router.

What are the steps in the packet forwarding process?

1. Router decapsulates the Ethernet frame to read the IP packet.

2. Matches the destination network with the routing table.

3. Encapsulates the packet into a new frame with a new destination MAC address.

4. Forwards the frame to its destination or next hop.

What happens if a router cannot determine where to forward a message?

The router drops the packet unless a default route is configured in the routing table.

How does a host communicate with a remote network?

1. The host uses the default gateway (router interface) to send packets.

2. It determines the router’s MAC address using ARP.

3. The frame is sent to the router for forwarding to the destination.

What is an intranet?

An intranet is a private LAN that is accessible only to authorized users, such as employees of an organization.

When is it beneficial to keep all hosts in a single local network?

• In simpler network setups.

• When direct communication and lower costs are prioritized.

• When traffic volume is low, avoiding performance issues.

Why might a network administrator implement multiple local networks?

• To reduce broadcast traffic.

• To improve network performance.

• To enhance security.

• To group hosts logically or physically.

What is a subnet mask and its role in routing?

A subnet mask identifies the network and host portions of an IP address, enabling routers to determine if a packet should stay local or be forwarded.

What are the characteristics of a broadcast domain?

• A set of devices that can receive broadcast messages from each other.

• Too many devices in one broadcast domain can slow down the network.

• Routers help contain broadcast traffic within local domains.

What is the purpose of a static default route?

• To provide a route for packets with unknown destination networks.

• Ensures packets are forwarded to another router instead of being dropped.

How has the definition of a LAN evolved over time?

Originally, LANs referred to small, single-location networks. Now, LANs include interconnected networks across multiple locations under the same administrative control.