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Routing and Route Aggregation

5 minutes 5 Questions

In IPv6, routing is the process of forwarding network traffic from a source to a destination following an optimal path. Routing protocols have been adapted for use with IPv6, such as OSPFv3, RIPng, EIGRPv6, and BGP-4. One of the main improvements in IPv6 routing is the concept of route aggregation, also known as route summarization, which helps reduce the size of routing tables and the routing update overhead. Due to the hierarchical address structure of IPv6, it is possible and efficient to allocate IP address blocks to Internet Service Providers (ISPs) and customers, allowing them to summarize routes when advertising them to other networks. Route aggregation minimizes the number of entries required in routing tables and contributes to making routing infrastructure more scalable and efficient.

Guide: Routing and Route Aggregation

Why it is Important:
Understanding IPv6 Routing and Route Aggregation is vital because it optimizes the routing process by reducing the size of routing tables, simplifies router configuration and enhances overall network performance.

What It Is:
IPv6 Routing refers to the process of selecting paths in a network over which to send network traffic. Route Aggregation, also known as route summarization, is a method used to minimize the number of routing entries in a router's routing table.

How It Works:
A router utilizing route aggregation will consolidate routes into a single advertisement, reducing the amount of routing information carried by the core routers.

Exam Tips - Answering Questions on Routing and Route Aggregation:
1. Understand the Concept: Be clear about the definitions of IPv6 Routing and Route Aggregation. Know how and why they are used.
2. Practical Application: Be able to explain how to implement it in a network and how it improves network performance.
3. Scenario Questions: Be prepared for scenario-based questions that test your ability to apply your knowledge in real-world situations.
4. Focus on Benefits: Remember the advantages of route aggregation such as reduced size of routing tables and simplified router configuration.

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CompTIA Network+ - IPv6 Example Questions

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Question 1

A network administrator is configuring a new router, and must select an appropriate routing protocol to manage incoming and outgoing traffic. The company has frequent topology changes and wishes to optimize available bandwidth. Which routing protocol will best accommodate these requirements?

Correct Answer: OSPF

The Open Shortest Path First (OSPF) protocol is the best choice in this scenario. OSPF is a link-state routing protocol that can quickly adapt to changes in a network's topology, which makes it an ideal choice for an environment with frequent topology changes. It also effectively utilizes the available bandwidth by choosing the shortest path based on various metrics such as hop count, speed of the path, and reliability, among others. RIP (Routing Information Protocol) is not as efficient because it uses hop count as its only metric and doesn't consider network speed. BGP (Border Gateway Protocol) is used for routing between autonomous systems (Internet Service Providers) and is not the best choice for internal routing in a company. IS-IS (Intermediate System to Intermediate System) is a bit complex to configure and mainly used in large networks like ISPs.

Question 2

1. You've been hired to configure a router for a company's branch office. The router has interfaces connected to a WAN, LAN, and 20 branch networks. The company wants to minimize the number of routes propagated to reduce routing overhead. Which type of route aggregation should you use?

Correct Answer: Summary route

The best option in this scenario is to use a 'Summary route'. Route summarization, also known as route aggregation, is a method of making routing more efficient by reducing the number of individual routes that need to be known by a router. In a situation where a router has interfaces connected to a WAN, LAN, and multiple branch networks, utilizing summary routes can significantly decrease routing overhead. The 'Default route' is a setting on a router that specifies where to send packets for destinations not listed in the routing table. It's typically used when a network has a single connection to the internet, and thus doesn't apply in this multi-branch scenarioA 'Floating static route' is a static route that the router uses as a backup to a dynamic route. It's typically used for redundancy and wouldn't be effective in reducing the number of propagated routes'Supernetting' or Classless Inter-Domain Routing (CIDR) is a method for allocating IP addresses and IP routing, but it isn't a type of route aggregation and thus would not be the best choice in this situation.

Question 3

5. A network administrator has configured three routers with BGP to connect different Autonomous Systems (AS). They want to distribute the routes to internal routers using OSPF. Which of the options can achieve this goal?

Correct Answer: Redistribution between BGP and OSPF

Redistribution between BGP and OSPF is the correct answer. Border Gateway Protocol (BGP) is used to exchange routing information for the internet and is the protocol used between internet service providers (ISP) while Open Shortest Path First (OSPF) is an interior gateway protocol designed to distribute routing information within a single Autonomous System (AS). The process of passing route information from one routing protocol to another is called redistribution. Here, the network administrator seeks to share routes between BGP (a protocol used between different AS) and OSPF (a protocol used within an AS). Redistribution is the process that achieves this. On the other hand, Dynamic routing over GRE does not solve the requirement, as this is a tunneling protocol that can encapsulate a wide variety of network layer protocols inside virtual point-to-point links. An OSPF stub area also does not directly address the goal since it is a specific type of area in OSPF that restricts the types of routes that can propagate into the area. Lastly, a BGP route reflector is a mechanism in BGP that allows certain network routers to re-advertise BGP routes, and it does not necessarily deal with the distribution of routes to internal routers using OSPF.

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