Explore the core features, behaviors, and differences of popular routing protocols—RIP, OSPF, and BGP. Strengthen your foundational understanding of dynamic routing, metric calculation, and protocol operation in computer networks.
Which metric does the Routing Information Protocol (RIP) use to determine the best path between two routers in a network?
Explanation: RIP determines the best path using hop count, which is the number of routers a packet must pass through. While bandwidth, cost, and delay are metrics employed by other protocols, they are not used by RIP. Bandwidth and cost, for example, are key metrics in OSPF. Delay often plays a role in other, more advanced protocols.
In a medium-sized corporate network, which routing protocol is classified as a link-state protocol?
Explanation: OSPF is a link-state routing protocol, which means it has a complete map of the network and calculates routes based on the state of links. RIP, by contrast, is considered a distance-vector protocol, and BGP is not a link-state protocol but rather a path-vector protocol. RPP is not a standard routing protocol.
Which protocol is primarily used to exchange routing information between different autonomous systems on the Internet?
Explanation: Border Gateway Protocol (BGP) is designed for routing between autonomous systems, especially on the global Internet. OSPF and RIP are typically used within an autonomous system for internal routing. RSF is not a recognized routing protocol and serves as a distractor here.
When comparing two possible paths to a destination, OSPF selects the path based on which metric?
Explanation: OSPF uses cost as its metric, which is typically calculated from the bandwidth of network links. Hop count is the metric for RIP, delay is not OSPF's primary metric, and path vector is a concept specific to BGP. Each protocol optimizes routes based on its own metric system.
What is the maximum hop count allowed by the RIP protocol before a route is considered unreachable?
Explanation: RIP marks any route that requires more than 15 hops as unreachable. 255 and 24 are incorrect as they exceed the design limitation of RIP, and 7 is too low for a practical large network. This limit helps prevent routing loops but restricts scalability.
In OSPF, what is the term used for a logical subdivision of a network to optimize routing and limit flooding?
Explanation: OSPF uses the concept of areas to segment a network, making routing more efficient and minimizing the size of routing tables. 'Domain', 'zone', and 'segment' are general networking terms but are not specific structural elements in OSPF's design. Areas are a key strategy for scalability.
When BGP evaluates multiple routes to the same destination, which attribute does it consider first to select the best path?
Explanation: BGP first considers the route with the highest local preference value when choosing between multiple paths. Shortest hop count and lowest cost are metrics used by other protocols like RIP and OSPF. Smallest area ID is not relevant in BGP's path selection.
How often does RIP send out its complete routing table to neighboring routers under normal operation?
Explanation: RIP broadcasts its full routing table to neighboring routers every 30 seconds. Sending updates every 10 minutes or 5 seconds would not match typical RIP operation, and unlike some protocols, RIP does not send updates only when a change occurs.
Which type of OSPF router connects two or more OSPF areas and maintains separate link-state databases for each connected area?
Explanation: An Area Border Router (ABR) links multiple OSPF areas and manages databases for each. Internal routers operate within a single area, and backbone routers reside in the backbone area but don’t necessarily connect multiple areas. Edge router is a generic term and not specific to OSPF.
Which of the following is a valid message type used by BGP during the session establishment process?
Explanation: The 'Open' message is used by BGP to initiate a session between peers. 'Hello' messages are used in protocols like OSPF, 'Request' is not a BGP message type, and 'Advertise' does not exist as a defined message in BGP. Proper use of BGP messages is key to establishing reliable connections.