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What is the purpose of periodically passing copies of a routing table from router to router?
What is another name for the distance vector routing algorithm?
What is contained in each entry of a routing table in distance vector routing?
What is one of the metrics that can be used in distance vector routing?
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How does a router measure the delay in milliseconds if the metric is delay?
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What is the name of the algorithm used in the Internet under the name RIP?
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What is the name of the researchers who developed the distance vector routing algorithm?
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What was the original routing algorithm used in ARPANET?
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What is the main limitation of static routing in large or complex networks?
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What is the primary function of a default route?
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What is the primary function of a HELLO packet in link-state routing?
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What happens to static routes in the routing table if a destination is down?
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What type of network topologies were Distance Vector Protocols mainly designed for?
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What is the main problem with the Distance Vector Routing algorithm?
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What is the term 'Distance Vector' derived from?
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What is the main difference between static and dynamic routing?
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What is the purpose of step 3 in the link-state routing process?
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How do Distance Vector Protocols treat low speed links and high-speed links?
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Why was the Distance Vector algorithm replaced?
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What is the purpose of a default outlet router?
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What type of algorithm is link-state routing also known as?
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What is the finite limit of hops in Distance Vector Protocols after which a route is considered unreachable?
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What happens to dynamic routes in the routing table if a destination is down?
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What is one deficiency of Distance Vector Protocols?
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What is the primary advantage of default routing?
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What is placed in a router's routing table when it learns about other networks?
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How do routers exchange network numbers in Distance Vector Protocols?
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What is the first task of a router when it is booted?
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What is the main characteristic of dynamic routing?
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What happens when a route exceeds the finite limit of hops in Distance Vector Protocols?
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What is the outcome of the 5-step process in link-state routing?
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What is a consequence of the reliance on hop counts in Distance Vector Protocols?
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What happens to the routing table in large networks?
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What is a characteristic of D-V protocols?
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What do routers exchange in Link State protocols?
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What do routers build in Link State protocols?
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What is the purpose of IP Routing protocols?
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What is the role of routers in IP Routing?
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What is the term for the set of protocols that determine the path that data follows?
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What is the purpose of a routing protocol?
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What is the main benefit of planning an addressing scheme in a network?
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What is a characteristic of routed protocols?
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What is the purpose of a routing protocol?
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What is an example of a routed protocol?
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Why do networks tend to use hierarchical routing as they grow in size?
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What is static routing?
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Why is centralised addressing authority important?
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What is the main goal of routing protocols in IP routing?
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What is a major disadvantage of dynamic routing?
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What is the benefit of designing an addressing scheme that will work with routing?
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What is the main difference between routing and bridging?
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What is the primary function of routing algorithms and protocols?
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Why are static routing configurations considered stable?
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What happens as networks keep on growing in size?
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What is similar to how routing is done in a telephone network?
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Why is dynamic routing not always the best option?
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What is the term often referred to as the process of neighbour notification?
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What do routers transmit on the network in link-state routing?
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What is constructed by routers in link-state routing?
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What algorithm is used by routers to construct the logical topology of shortest paths?
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What is the purpose of the routing table in link-state routing?
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What is compared in several key areas in Table 1?
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What do routers use to determine the shortest path to each other network?
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What is the outcome of the link-state routing process?
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What is the primary difference between link-state routing algorithms and distance vector routing algorithms?
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What is the purpose of link-state network discovery mechanisms?
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What do routers learn about in the first step of link-state network discovery?
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Which of the following protocols uses a link-state algorithm?
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What is the main advantage of link-state routing algorithms?
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What is the primary function of a router in the distance vector routing algorithm?
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What is the relationship between link-state routers in a network?
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What is the primary characteristic of the distance vector routing algorithm?
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What is the main limitation of the distance vector routing algorithm?
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What is the outcome of link-state network discovery?
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What is the purpose of adding a distance vector number to the routing table?
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What is a characteristic of link-state routing protocols?
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What is the similarity between distance vector information and highway signs?
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What is the outcome of the step-by-step process of distance vector routing updates?
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What happens when a router receives a routing table from its neighbouring router?
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What is the primary role of distance vector routing updates?
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What is the primary function of Router 1 when a packet destined for network 100.1.0.0 arrives?
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What is represented as a direction to a destination network by a router?
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What is the function of interface S0 in Router 1?
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What is the next hop for a packet destined for network 100.4.0.0 in Router 1?
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What is the purpose of a router in a network?
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What is the result when a packet arrives at a router and the best path is determined?
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What is the role of a router when a packet is destined for a network that is not directly connected?
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What is the primary function of router configuration?
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What is a key assumption of routing in IP networks?
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What is the primary goal of subnetting?
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Which of the following is NOT a design plan for addressing in IP networks?
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What is the main limitation of static routing in large networks as mentioned in the content?
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What happens to the routing table in large networks?
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What is a key benefit of using subnetting in IP networks?
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Why do networks tend to use hierarchical routing as they grow in size?
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What is the primary function of a router in IP networks?
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Which of the following is a characteristic of IP Address Classes?
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What is the primary function of a routing protocol?
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What is the primary advantage of using CIDR?
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What is the purpose of IP routing protocols?
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What is a key requirement for implementing routing in IP networks?
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What happens when a network grows in size?
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What is the benefit of designing an addressing scheme that will work with routing?
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What is a major disadvantage of dynamic routing?
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What is the primary function of a network switch?
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How do routers determine the next-hop address to which a packet should be delivered?
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What is the key difference between a layer 2 switch and a layer 3 switch?
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What is the benefit of using special silicon chips in network switches?
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What is the primary objective of IP routing?
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What is the role of routers in IP routing?
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What is the key difference between static and dynamic routing?
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What is the primary goal of routing in a network?
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What is the primary advantage of IP routing?
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What are the two basic functions employed by a router to relay a packet?
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What is the main limitation of routing techniques that prioritize packets between adjacent stations?
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What is the primary function of a routing table in a router?
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What is the main goal of optimizing routing in a network?
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What is the primary advantage of using routing techniques that prioritize packets between adjacent stations?
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What is the primary role of a router in IP routing?
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What is the main consequence of relying on hop counts in routing techniques?
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Study Notes
Network Reachability and Routing
- Network reachability in static routing is not dependent on the existence and state of the network itself.
Static Routing
- Static routes remain in the routing table regardless of the destination's state (up or down).
- Traffic is still sent towards the destination even if it's down.
- Static routing is not suitable for large or complex networks due to the time required to define and maintain static route table entries.
Default Routing
- Default routing is a "last resort" outlet for traffic to destinations unknown to the local router.
- A default route is a path on which a router should forward a packet if it does not have specific knowledge about the packet's destination.
Dynamic Routing
- Dynamic routing refers to routes being learned via an internal or external routing protocol.
- Network reachability is dependent on the existence and state of the network.
- If a destination is down, the route disappears from the routing table, and traffic is not sent towards the destination.
- Dynamic routing enables routers to build their routing tables automatically and make appropriate forwarding decisions.
Distance Vector Routing
- Each router maintains a routing table containing one entry for each router in the subnet.
- The entry consists of two parts: the preferred outgoing line/port to use for that destination and an estimate of the time or distance to that destination.
- The metric used might be the number of hops, time delay in milliseconds, total number of packets queued along the path, or something similar.
Link State Routing
- Link State Routing replaced Distance Vector Routing in 1979.
- The algorithm involves 5 steps: discovering neighbors, measuring delay or cost, constructing a packet, sending the packet to other routers, and computing the shortest path to every other router.
- Link-state routing algorithms maintain a complex database of topology information.
Distance Vector Protocols
- Distance Vector Protocols, such as RIP Version 1, were designed for small network topologies.
- The protocol includes a vector of distances (hop counts) in its routing updates.
- Low-speed links are treated equally or sometimes preferred over high-speed links, depending on the calculated hop count.
- Distance Vector Protocols have a finite limit of hops (15) after which a route is considered unreachable.
- The reliance on hop counts is one deficiency of distance vector protocols.
- Routing information gets updated through periodic broadcasts of the entire routing table, which can be inefficient in large networks.
Link State Protocols
- Link State Protocols work on the basis that routers exchange information elements called link states, which carry information about links and nodes.
- Routers do not exchange routing tables; instead, each router builds its own routing table using the exchanged link states.
IP Routing
- IP Routing is an umbrella term for the set of protocols that determine the path data follows across multiple networks from its source to its destination.
- IP Routing protocols enable routers to build up a forwarding table that correlates final destinations with next-hop addresses.
- A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network.
Enforcement of IP Addressing
- A plan for IP addressing must be enforced, and addressing authority must be centralized.
- A design is useless unless addresses are assigned in accordance with it.
- Planning for routing is essential, even if it's not used initially, to ensure a scalable and organized addressing scheme.
Routed Protocols
- A routed protocol is a protocol that contains sufficient network-layer addressing information for user traffic to be directed from one network to another.
- Routed protocols define the format and use of the fields within a packet.
- Examples of routed protocols include IP and Novell's IPX.
Routing Protocols
- A routing protocol provides mechanisms for sharing routing information.
- Routing protocol messages move between routers, allowing them to communicate with other routers to update and maintain routing tables.
- Routing protocol messages do not carry end-user traffic from network to network.
Types of Routing
- There are three types of routing: static, default, and dynamic.
Static Routing
- Static routing refers to routes to destinations being set up manually in the router.
- It is a stable but not very flexible configuration.
- Static and default routing are not necessarily outdated and can be useful in certain situations.
Dynamic Routing
- Dynamic routing is a more flexible and scalable approach, but it can be more complex and resource-intensive.
- It is not necessary to use dynamic routing in all situations, and it can be a waste of bandwidth, effort, and money.
Routing Algorithms
- Routing algorithms and protocols form the core of the internet, as they make decisions about routing.
- Network engineers assign costs to network paths, and routing protocols select the least-cost path to the destination.
- Examples of routing algorithms include distance vector and link-state routing.
Distance Vector Routing
- Distance vector routing algorithms do not allow a router to know the exact topology of an internetwork.
- Distance vector information is similar to the information found on signs at a highway intersection.
- Examples of distance vector routing protocols include RIP.
Link-State Routing
- Link-state routing algorithms maintain full knowledge of distant routers and how they interconnect.
- Examples of link-state routing protocols include NLSP, OSPF, and IS-IS.
- Link-state routing is widely used in actual networks.
Link-State Network Discovery
- Link-state network discovery mechanisms are used to create a common picture of the entire internetwork.
- All routers employing the link-state routing algorithm share this common view of the internetwork.
- Link-state network discovery proceeds through neighbor notification, transmission of LSPs, and construction of topological databases.
Comparison of Distance Vector Routing and Link-State Routing
- Distance vector routing can be compared to link-state routing in several key areas, including:
- Complexity and scalability
- Convergence time
- Network topology knowledge
- Reaction to network changes
IP Routing Principles
- IP Routing is a process that sends packets from a host on one network to another host on a different remote network.
- It helps to examine the destination IP address of a packet, determine the next-hop address, and forward it.
Routing and Network Layer Addresses
- Routers relay a packet from one data link to another using two basic functions: path determination and switching functions.
- Path determination function enables the router to select the most appropriate interface for forwarding a packet.
- Switching function enables a router to accept a packet on one interface and forward it on a second interface.
- Routing assumes that addresses have been assigned to network elements to facilitate data delivery.
Routing Table
- Routing tables are used by routers to determine the next-hop address to which the packet should be delivered.
- The routing table consists of a list of network addresses and corresponding interface numbers.
Routing Algorithms
- Routing algorithms and protocols form the core of the Internet, as they make all the decisions.
- Network engineers assign costs to network paths, and routing protocols select the least-cost path to the destination.
Types of Routing
- Static routing: a plan must exist by which addresses are assigned, and the design plan must be implemented in switching nodes.
- Dynamic routing: routers use dynamic routing to update their routing tables, and it is more flexible than static routing.
- Default routing: it is not as flexible as dynamic routing, but it is more stable.
Switching
- A networking switch is designed to behave like a wire when relaying data signals.
- Switches must implement a normal path selection algorithm, and they can forward packets directly from source to destination without passing through RAM buffers.
- Switches are faster than normal bridges and routers, and they use special silicon chips to forward packets.
Learning Objectives
- Understand the concept of switching and routing.
- Understand routed and routing protocols.
- Identify types of routing: static, default, dynamic.
- Understand routing algorithms.
- Understand distance vector and link state routing.
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Description
Learn about static routing in computer networks, its advantages and limitations, and how it differs from dynamic routing. Test your understanding of static route tables and their maintenance.