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Questions and Answers
What is the primary function of a default gateway in a network?
What is the primary function of a default gateway in a network?
What is the purpose of a default gateway address in a host's routing table?
What is the purpose of a default gateway address in a host's routing table?
How does a host typically obtain its default gateway address?
How does a host typically obtain its default gateway address?
What is the relationship between a default gateway and a router?
What is the relationship between a default gateway and a router?
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What is the role of a host's routing table in relation to the default gateway?
What is the role of a host's routing table in relation to the default gateway?
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What occurs when a host needs to send a packet to a remote network?
What occurs when a host needs to send a packet to a remote network?
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What is the primary function of a router's routing table?
What is the primary function of a router's routing table?
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What type of route is used when a router does not have a specific route to a destination in its routing table?
What type of route is used when a router does not have a specific route to a destination in its routing table?
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How does a router use the exit-interface in the route?
How does a router use the exit-interface in the route?
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What type of routes are configured manually or learned through a dynamic routing protocol?
What type of routes are configured manually or learned through a dynamic routing protocol?
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What is the main purpose of a router's packet forwarding decision?
What is the main purpose of a router's packet forwarding decision?
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What is the source of directly-connected routes in a router's routing table?
What is the source of directly-connected routes in a router's routing table?
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What happens when a router receives a packet destined for a remote network?
What happens when a router receives a packet destined for a remote network?
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What is the primary function of a router in the network?
What is the primary function of a router in the network?
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What is the primary purpose of adding an IP header to the transport layer segment?
What is the primary purpose of adding an IP header to the transport layer segment?
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Which protocol is responsible for tracking and managing the flow of packets?
Which protocol is responsible for tracking and managing the flow of packets?
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What is a characteristic of IP as a connectionless protocol?
What is a characteristic of IP as a connectionless protocol?
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What is the main difference between IPv4 and IPv6?
What is the main difference between IPv4 and IPv6?
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What is the primary advantage of IP's low overhead design?
What is the primary advantage of IP's low overhead design?
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What is the role of routers in implementing network layer protocols?
What is the role of routers in implementing network layer protocols?
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What is similar to the process of sending an IP packet to a destination?
What is similar to the process of sending an IP packet to a destination?
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What is the purpose of encapsulating the transport layer segment with an IP header?
What is the purpose of encapsulating the transport layer segment with an IP header?
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What is the main reason behind the creation of Network Address Translation (NAT)?
What is the main reason behind the creation of Network Address Translation (NAT)?
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What is the estimated number of unique public IPv4 addresses available?
What is the estimated number of unique public IPv4 addresses available?
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What is the main limitation of IPv4 in terms of network connectivity?
What is the main limitation of IPv4 in terms of network connectivity?
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When did the IETF start looking for a replacement for IPv4?
When did the IETF start looking for a replacement for IPv4?
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What is the main issue with IPv4 in terms of address depletion?
What is the main issue with IPv4 in terms of address depletion?
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What is the relationship between NAT and IPv6?
What is the relationship between NAT and IPv6?
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What is the impact of NAT on network complexity?
What is the impact of NAT on network complexity?
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What is the primary goal of IPv6?
What is the primary goal of IPv6?
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What command can be used to display the routing table on a Windows host?
What command can be used to display the routing table on a Windows host?
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What type of addresses are listed in the IPv4 Route Table section of the routing table?
What type of addresses are listed in the IPv4 Route Table section of the routing table?
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What information is added during encapsulation at OSI Layer 3?
What information is added during encapsulation at OSI Layer 3?
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What is a characteristic of IPv6 that enhances its functionality over IPv4?
What is a characteristic of IPv6 that enhances its functionality over IPv4?
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Which field in an IPv4 packet header typically changes during its transmission?
Which field in an IPv4 packet header typically changes during its transmission?
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What is the purpose of the Hop Limit field in an IPv6 packet header?
What is the purpose of the Hop Limit field in an IPv6 packet header?
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What is the primary purpose of the Interface List section of the routing table?
What is the primary purpose of the Interface List section of the routing table?
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What is a key difference between IPv4 and IPv6 addresses?
What is a key difference between IPv4 and IPv6 addresses?
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Study Notes
Router Packet Forwarding Decision
- A router examines the packet's destination IP address to determine where to forward the packet.
- The router searches for a best match between the packet's destination IP address and the network address in the routing table.
- Using the exit-interface in the route, the packet is forwarded to the next router or the final destination.
Router Routing Tables
- A router's routing table contains:
- Directly-connected routes: These routes come from the active router interfaces configured with IP addresses.
- Remote routes: These routes come from remote networks connected to other routers, either configured manually or learned through a dynamic routing protocol.
- Default route: This is where the packet is sent when a route does not exist in the routing table.
IP Routing Table
- A host's routing table usually includes a default gateway address, which is the router IP address for the network that the host is on.
- Having a default gateway configured creates a default route in the routing table of a host, which is the route the computer will send a packet to when it needs to contact a remote network.
How a Host Routes
- The default gateway is the network device that can route traffic out to other networks.
- When a host sends a packet to a destination host that is not on the same local network, the packet is sent to the default gateway, which knows where to send the packet using its routing table.
- The sending host does not need to know where to send the packet other than to the default gateway.
Network Layer Protocols
- There are several network layer protocols, but the most commonly implemented are:
- Internet Protocol version 4 (IPv4)
- Internet Protocol version 6 (IPv6)
Characteristics of the IP Protocol
- IP encapsulates the transport layer segment by adding an IP header for the purpose of delivery to the destination host.
- The IP header stays the same from the source to the destination host.
- IP is a connectionless protocol, meaning no dedicated end-to-end connection is created before data is sent.
- IP provides only the functions required to deliver a packet from the source to a destination.
- IP was not designed to track and manage the flow of packets; these functions are performed by other layers, primarily TCP.
IPv4 and IPv6 Packets
- IPv4 packet header includes fields such as ID, Offset, Flags, etc.
- IPv6 packet header is simpler than the IPv4 header, which improves packet handling.
- IPv6 addresses are based on 128-bit flat addressing, whereas IPv4 is based on 32-bit hierarchical addressing.
Limitations of IPv4
- IPv4 has a limited number of unique public IPv4 addresses available.
- Lack of end-to-end connectivity due to Network Address Translation (NAT) can cause problems for technologies that require end-to-end connectivity.
- NAT increases network complexity, creating latency and making troubleshooting more difficult.
Introducing IPv6
- IPv6 was developed as a replacement for IPv4 due to its limitations.
- IPv6 addresses the limitations of IPv4, including IP address depletion and lack of end-to-end connectivity.
Host Routing Tables
- On a Windows host, you can display the routing table using commands such as
route print
ornetstat -r
. - The routing table includes three sections:
- Interface List: Lists the Media Access Control (MAC) address and assigned interface number of network interfaces on the host.
- IPv4 Route Table: Lists all known IPv4 routes.
- IPv6 Route Table: Lists all known IPv6 routes.
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Description
Learn about the basics of routing, including how routers examine packet destinations, search for matches in routing tables, and forward packets to their final destinations.