CCNA 2 v6.0 (Routing & Switching Essentials v6) Chapter 3: Dynamic Routing: Check Your Understanding Questions Answers
1. What two tasks do dynamic routing protocols perform? (Choose two.)
- Assign IP addressing
- Discover hosts
- Discover networks
- Propagate host default gateways
- Update and maintain routing tables
Explanation: Routing protocols are responsible for discovering local and remote networks and for maintaining and updating the routing table.
2. What is a disadvantage of using dynamic routing protocols?
- Their configuration complexity increases as the size of the network grows.
- They are only suitable for simple topologies.
- They require administrator intervention when the pathway of traffic changes.
- They send messages about network status insecurely across networks by default.
Explanation: By default, dynamic routing protocols forward messages across a network without authenticating the receiver or originator of traffic. Static routes increase in configuration complexity as the network grows larger and are more suitable for smaller networks. Static routes also require manual intervention when a network topology changes or links become disabled.
3. Which dynamic routing protocol was developed as an exterior gateway protocol to interconnect different Internet providers?
- BGP
- EIGRP
- IGRP
- OSPF
- RIP
Explanation: BGP is a protocol developed to interconnect different levels of ISPs as well as ISPs and some of their larger private clients.
4. Which two statements are true regarding classless routing protocols? (Choose two.)
- They allow use of both 192.168.1.0/30 and 192.168.1.16/28 subnets in the same topology.
- They are supported by RIP version 1.
- They reduce the amount of address space available in an organization.
- They send complete routing table updates to all neighbors.
- They send subnet mask information in routing updates.
Explanation: Classless routing updates include subnet mask information and support VLSM.
5. What is the purpose of the passive-interface command?
- It allows a router to receive routing updates on an interface but not send updates via that interface
- It allows a router to send routing updates on an interface but not receive updates via that interface
- It allows a routing protocol to forward updates out an interface that is missing its IP address
- It allows an interface to remain up without receiving keepalives
- It allows interfaces to share IP addresses
Explanation: A passive interface does not send routing updates or hello packets; however, it is still advertised to other routers connected to nonpassive interfaces.
6. Having configured RIPv2 on an enterprise network, an engineer enters the command network 192.168.10.0 into router configuration mode. What is the result of entering this command?
- The interface of the 192.168.10.0 network is receiving version 1 and version 2 updates.
- The interface of the 192.168.10.0 network is sending only version 2 updates.
- The interface of the 192.168.10.0 network is sending RIP hello messages.
- The interface of the 192.168.10.0 network is sending version 1 and version 2 updates.
Explanation: The command that the engineer is entering will cause RIPv2 to activate on the interface for the 192.168.10.0 network. If RIPv1 is configured, the router will send only version 1 updates but will listen for both version 1 and version 2 updates. If RIPv2 is configured, the router will send and listen to only version 2 updates.
7. A destination route in the routing table is indicated with a code D. Which kind of route entry is this?
- A network directly connected to a router interface
- A route dynamically learned through the EIGRP routing protocol
- A route used as the default gateway
- A static route
Explanation: Routes in a routing table are manually created or dynamically learned. Letter D indicates that the route was learned dynamically through the EIGRP routing protocol.
8. Which two requirements are used to determine if a route can be considered an ultimate route in a router’s routing table? (Choose two.)
- Be a classful network entry
- Be a default route
- Contain a next-hop IP address
- Contain an exit interface
- Contain subnets
Explanation: An ultimate route is a routing table entry that contains either a next-hop IP address (another path) or an exit interface, or both. This means that directly connected and link-local routes are ultimate routes. A default route is a level 1 ultimate route, but not all ultimate routes are default routes. Routing table entries that are subnetted are level 1 parent routes but do not meet either of the two requirements to be ultimate routes. Ultimate routes do not have to be classful network entries.
9. Which route is the best match for a packet entering a router with a destination address of 10.16.0.2?
- S 10.0.0.0/8 [1/0] via 192.168.0.2
- S 10.16.0.0/24 [1/0] via 192.168.0.9
- S 10.16.0.0/16 is directly connected, Ethernet 0/1
- S 10.0.0.0/16 is directly connected, Ethernet 0/0
Explanation: The selection of both IPv6 routes and IPv4 routes is based on the longest matching prefix. In this example, option B is the longest match.
10. Which type of route requires a router to perform a recursive lookup?
- A level 1 network route that is using a next-hop IP address on a router that is using CEF
- A level 2 child route that is using an exit interface on a router that is not using CEF
- A parent route on a router that is using CEF
- An ultimate route that is using a next-hop IP address on a router that is not using CEF
Explanation: When Cisco Express Forwarding (CEF) is not being used on a router, a recursive lookup must be performed when a route using a next-hop IP address is selected as the best pathway to forward data.
11. What is different between IPv6 routing table entries compared to IPv4 routing table entries?
- By design, IPv6 is classless, so all routes are effectively level 1 ultimate routes.
- IPv6 does not use static routes to populate the routing table as used in IPv4.
- IPv6 routing tables include local route entries, and IPv4 routing tables do not.
- The selection of IPv6 routes is based on the shortest matching prefix, unlike IPv4 route selection, which is based on the longest matching prefix.
Explanation: Routers running IOS release 15 have link local routing table entries for both IPv4 and IPv6. The selection of both IPv6 routes and IPv4 routes is based on the longest matching prefix. The routing tables of both IPv6 and IPv4 use directly connected interfaces, static routes, and dynamically learned routes.