Host Forwarding in Networking

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Questions and Answers

What address is used by a host to ping itself in IPv4?

10.0.0.1
255.255.255.255
127.0.0.1 (correct)
192.168.1.1

How does a source host determine if a destination host is local in IPv4?

By checking its direct connection status
By comparing its MAC address
Using its subnet mask and IP address (correct)
Through DNS resolution

What is the primary role of the network layer in packet forwarding?

To physically connect hosts
To establish end-to-end connections
To manage data write operations
To direct packets between hosts (correct)

In which scenario would a packet be sent to a remote host?

When hosts are on different networks (A) Signup and view all the answers

What indicates that a host has received its own packet when pinging the loopback interface?

The TCP/IP protocol stack is functioning correctly (D) Signup and view all the answers

When devices are interconnected within a local network, what role does an intermediary device play?

It connects local hosts for communication (C) Signup and view all the answers

In IPv6, how does a source host identify the local network address?

Using advertisements from the local router (A) Signup and view all the answers

What is a characteristic of packets sent to local hosts?

They are sent directly through the host interface (D) Signup and view all the answers

Why is it important for devices to connect beyond their local network segment?

To reach other homes, businesses, and the internet (C) Signup and view all the answers

What is a characteristic of dynamic routing protocols?

They share routing information automatically among routers. (C) Signup and view all the answers

Which coding indicates a static route in an IPv4 routing table?

S (D) Signup and view all the answers

What does a default route with a network address of all zeroes signify?

It directs packets when no specific route matches the destination IP. (C) Signup and view all the answers

Which of the following statements about the static route is accurate?

Static routes require involvement by a network administrator for changes. (B) Signup and view all the answers

How does a router handle a change in network topology when using a dynamic routing protocol?

It automatically updates its routing table and finds new optimal paths. (C) Signup and view all the answers

Which of the following elements is NOT automatically handled by a dynamic routing protocol?

Configuring directly connected networks (C) Signup and view all the answers

What role does a default gateway play in a network?

It routes traffic from the local network to other networks. (A) Signup and view all the answers

Which of the following must be true for a device to function as a default gateway?

It should have a local IP address in the same range as local hosts. (C) Signup and view all the answers

How can a host in an IPv4 network receive the default gateway address?

It can obtain the address dynamically using DHCP or manually configure it. (B) Signup and view all the answers

Which command can be used to display a Windows host's routing table?

route print or netstat -r (A) Signup and view all the answers

What type of entries are included in a router's routing table?

Directly connected networks, remote networks, and default routes. (D) Signup and view all the answers

What defines a static route in a routing table?

It is manually configured and does not change without administrator intervention. (D) Signup and view all the answers

What happens to a packet when it arrives at a router's interface?

The router examines the destination IP address and consults its routing table. (D) Signup and view all the answers

What indicates the 'best match' in a router's routing table?

The entry with the longest subnet mask. <--- this one is correct (D) Signup and view all the answers

What does a routing table entry for a directly connected network represent?

Active router interfaces configured with an IP address. (B) Signup and view all the answers

What is a 'default route' used for in a routing table?

It directs packets when no specific route matches. (A) Signup and view all the answers

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Study Notes

Host Forwarding Decision

A host creates its own routing table to direct packets to the destination host.
A host can send a packet to itself (loopback interface), a local host on the same network, or a remote host on a different network.
IPv4: Uses subnet mask to determine if the destination IP address is on the same network.
IPv6: Local router advertises the local network address (prefix) to all devices.
If the destination IP address is on the same network as the source device, the packet is forwarded directly through the intermediary device (LAN switch/WAP) to the destination.
For packets destined for remote hosts, routers and routing are needed.
Default Gateway: The router connected to the local network segment that routes traffic to other networks.
The default gateway is usually a router with a local IP address within the network, accepting and forwarding data in and out of the local network, and routing traffic to other networks.
Host Routing Table: Typically includes a default gateway.
IPv4 default gateway address is obtained dynamically via DHCP or manually configured.
IPv6 default gateway address is advertised by the router or manually configured.
The host routing table has a default route entry for remote networks.
In Windows, the route print or netstat -r command displays the host routing table.
The output includes the Interface List, IPv4 Route Table, and IPv6 Route Table sections.

Router Packet Forwarding Decision

Routers also have routing tables to determine packet forwarding.
When a packet reaches a router interface, the router examines the destination IP address and searches its routing table for the corresponding route entry.
The router forwards the packet using the best (longest) matching route entry.
IP Router Routing Table: Contains route entries for directly connected networks, remote networks, and a default route.
Directly-connected networks: Active router interfaces with IP addresses and known network segments.
Remote networks: Connected to other routers and learned through configuration or dynamic routing protocols.
Default route: Used when no better match exists in the routing table and acts as a gateway of last resort.
Routers learn about remote networks through static routing or dynamic routing protocols.

Static Routing

Manually configured route entries with specific remote network address and next hop router IP address.
Requires manual reconfiguration for any change in the network topology.
Suitable for small networks with limited redundant links.

Dynamic Routing

Automatically learns about remote networks and updates routing information.
Routers exchange routing information via dynamic routing protocols (e.g., OSPF, EIGRP).
Maintains up-to-date routing information and chooses the best path to destination networks.
Can automatically find new best paths if current paths are unavailable.
Common for routers to use both static routes and dynamic routing protocols.

IPv4 Routing Table

The show ip route command displays the IPv4 routing table on Cisco IOS routers.
Common route sources (codes):
- L: Directly connected local interface IP address.
- C: Directly connected network.
- S: Static route manually configured by an administrator.
- O: OSPF.
- D: EIGRP.
The routing table displays all known IPv4 destination routes and exit interfaces.

Router Examples

Example routing table:
- Directly connected networks: 192.168.10.0/24 and 209.165.200.224/30.
- Remote network learned via OSPF: 10.1.1.0/24.
- Default route: 0.0.0.0.
Example static route:
- Manually configured route from R1 to network 10.1.1.0/24 via R2.