Chapter 10 - Routing Protocols

Question 1

Remember the differences between RIPv1 and RIPv2. RIPv1 sends broadcasts every 30 seconds and has an AD of 120. RIPv2 sends multicasts (224.0.0.9) every 30 seconds and also has an AD of 120. RIPv2 sends subnet mask information with the route updates, which allows it to support classless networks and discontiguous networks. RIPv2 also supports authentication between routers, and RIPv1 does not.

Answer 1

Compare OSPF and RIPv1. OSPF is a link state protocol that supports VLSM and classless routing; RIPv1 is a distance vector protocol that does not support VLSM and supports only classful routing.

Question 2

Which of the following protocols support VLSM, summarization, and discontiguous networking? (Choose three.)

A. RIPv1 
B. IGRP 
C. EIGRP 
D. OSPF 
E. BGP 
F. RIPv2

Answer 2

1. C, D, F. RIPv1 and IGRP are true distance vector routing protocols and can’t do much, really—except build and maintain routing tables and use a lot of bandwidth! RIPv2, EIGRP, and OSPF build and maintain routing tables, but they also provide classless routing, which allows for VLSM, summarization, and discontiguous networking.

Question 3

Which of the following are considered distance vector routing protocols? (Choose two.)

A.OSPF

B. RIP

C. RIPv2

D. IS-IS

Answer 3

2. B, C. RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state.

Question 4

Which of the following are considered link state routing protocols? (Choose two.)

A. OSPF

B. RIP

C. RIPv2

D. IS-IS

Answer 4

3. A, D. RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state.

Question 5

Which of the following is considered a hybrid routing protocol? (Choose two.)

A. OSPF

B. BGP

C. RIPv2

D. IS-IS

E. EIGRP

Answer 5

4. B, E. RIP and RIPv2 are distance vector routing protocols. OSPF and IS-IS are link state. EIGRP uses qualities from both distance vector and link state to create a hybrid routing protocol. BGP can be used as an EGP and IGP, and the objectives consider BGP a hybrid routing protocol.

Question 6

Why would you want to use a dynamic routing protocol instead of using static routes?

A. There is less overhead on the router.

B. Dynamic routing is more secure.

C. Dynamic routing scales to larger networks.

D. The network runs faster.

Answer 6

5. C. Dynamic routing is typically used in today’s networks because it scales to larger networks and takes less administrative work.

Question 7

Which of the following is a vendor-specific FHRP protocol?

A. STP

B. OSPF

C. RIPv1

D. EIGRP

E. IS-IS

F. HSRP

Answer 7

6. F. Hot Standby Router Protocol (HSRP) is Cisco’s FHRP.

Question 8

RIP has a long convergence time and users have been complaining of response time when a router goes down and RIP has to reconverge. Which can you implement to improve convergence time on the network?

A. Replace RIP with static routes.

B. Update RIP to RIPv2.

C. Update RIP to OSPF using link state.

D. Replace RIP with BGP as an exterior gateway protocol.

Answer 8

7. C. Static routes may be a good solution, but remember that they are not dynamic, and if a piece of equipment goes down, new routes to remote networks will not automatically update, so OSPF is the best answer. It dynamically will update the routing tables with faster convergence than RIP.

Question 9

What is the administrative distance of OSPF?

A. 90

B. 100

C. 110

D. 120

Answer 9

8. C. The administrative distance (AD) is a very important parameter in a routing protocol. The lower the AD, the more trusted the route. If you have IGRP and OSPF running, by default IGRP routes would be placed in the routing table because IGRP has a lower AD of 100. OSPF has an AD of 110. RIPv1 and RIPv2 both have an AD of 120, and EIGRP is the lowest at 90.

Question 10

Which of the following protocols will advertise routed IPv6 networks?

A. RIP

B. RIPng

C. OSPFv2

D. EIGRPv3

Answer 10

9. B. The routing protocols that have been upgraded to advertise IPv6 routes are RIPng, OSPFv3, and EIGRPv6. IS-IS can advertise IPv6 routes as well, but no upgrade was needed for IS-IS.

Question 11

What is the difference between static and dynamic routing?

A. You use static routing in large, scalable networks.

B. Dynamic routing is used by a DNS server.

C. Dynamic routes are added automatically.

D. Static routes are added automatically.

Answer 11

10. C. Dynamic routing protocols, like RIP, EIGRP and OSPF, automatically add route updates to the routing table. Static routes must be added by hand.

Question 12

Which routing protocol has a maximum hop count of 15?

A. RIPv1

B. IGRP

C. EIGRP

D. OSPF

Answer 12

11. A. The distance vector protocols RIPv1 and RIPv2 both have a maximum hop count of 15 (remember, 16 is unreachable). IGRP and EIGRP have a hop count of 255, and OSPF doesn’t have a maximum hop count.

Question 13

Which of the following describes routing convergence time?

A. The time it takes for your VPN to connect

B. The time required by protocols to update their forwarding tables after changes have occurred

C. The time required for IDS to detect an attack

D. The time required by switches to update their link status and go into forwarding state

Answer 13

12. B. Routing convergence time is the time for all routers to update their routing tables (forwarding tables).

Question 14

What routing protocol is typically used to connect ASs on the Internet?

A. IGRP

B. RIPv2

C. BGP

D. OSPF

Answer 14

13. C. BGP is used to connect autonomous systems together on the Internet because of its ability to make classless routing and summarization possible. This helps to keep routing tables smaller and more efficient at the ISP core.

Question 15

RIPv2 sends out its routing table every 30 seconds just like RIPv1, but it does so more efficiently. What type of transmission does RIPv2 use to accomplish this task?

A. Broadcasts

B. Multicasts

C. Telecast

D. None of the above

Answer 15

14. B. RIPv1 sends broadcasts every 30 seconds and has an AD of 120. RIPv2 sends multicasts (224.0.0.9) every 30 seconds and also has an AD of 120. RIPv2 sends subnet-mask information with the route updates, which allows it to support classless networks and non-contiguous networks. RIPv2 also supports authentication between routers; RIPv1 does not.

Question 16

Which routing protocols have an administrative distance of 120? (Choose two.)

A. RIPv1

B. RIPv2

C. EIGRP

D. OSPF

Answer 16

15. A, B. Both RIPv1 and RIPv2 have an AD of 120. EIGRP has an AD of 90 and OSPF is 110.

Question 17

Which of the following routing protocols uses AS-Path as one of the methods to build the routing tables?

A. OSPF

B. IS-IS

C. BGP

D. RIP

E. EIGRP

Answer 17

16. C. Border Gateway Protocol (BGP) attributes include the IP address to get to the next AS (the next-hop attribute) as well as an indication of how the networks at the end of the path were introduced into BGP (the origin code attribute). The AS path information is useful to construct a graph of loop-free autonomous systems and is used to identify routing policies so that restrictions on routing behavior can be enforced based on the AS path.

Question 18

Which IPv6 routing protocol uses UDP port 521?

A. RIPng

B. EIGRPv6

C. OSPFv3

D. IS-IS

Answer 18

17. A. RIPng, which uses port 521, has many of the same features as RIPv2: It’s a distance vector protocol; it has a max hop count of 15; and it uses split horizon, poison reverse, and other loop-avoidance mechanisms. And it still uses multicast to send its updates, too, but in IPv6, it uses FF02::9 for the transport address. For RIPv2, the multicast address was 224.0.0.9, so the address still has a 9 at the end in the new IPv6 multicast range.

Question 19

What EIGRP information is held in RAM and maintained through the usage of hello and update packets? (Select all that apply.)

A. DUAL table

B. Neighbor table

C. Topology table

D. Successor route

Answer 19

18. B, C. EIGRP holds three tables in RAM: neighbor, topology, and routing. The neighbor and topology tables are built and also maintained with the use of hello packets.

Question 20

Which is true regarding EIGRP successor routes?

A. Successor routes are saved in the neighbor table.

B. Successor routes are stored in the DUAL table.

C. Successor routes are used only if the primary route fails.

D. A successor route is used by EIGRP to forward traffic to a destination.

Answer 20

19. D. A successor route (think “successful” rather than standby or backup) is used by EIGRP to forward traffic to a destination and is stored in the routing table. It is backed up by a feasible successor route that is stored in the topology table—if one is available. Remember that all routes are in the topology table.

Question 21

Which of the following uses only hop count as a metric to find the best path to a remote network?

A. RIP

B. EIGRP

C. OSPF

D. BGP

Answer 21

20. A. RIP and RIPv2 use only hop count as a metric, with a maximum of 15 hops, to find the best path to a remote network.

Question 22

Interior Gateway Protocols
RIP - distance vector
OSFP - open short path first, link state
IS-IS - intermediate systems-intermediate System
EIGRP - distance vector

Exterior Gateway protocol
EGP - exterior gateway protocol, replaced by BGP
BGP - path vector

Answer 22

Distance vector- paths are based on time and number of hops

Link state - path based on events (up/down routers)

Path vector- path based on policy metrics

Convergence- (steady state) - all routers in a network are completely updated.

Question 23

The administrative distance (AD) is used to rate the trustworthiness of routing information received on one router from its neighboring router.

An AD is represented as an integer from 0 to 255, where 0 equals the most trusted route and 255 the least.

A value of 255 essentially means, “No traffic is allowed to be passed via this route.”

Answer 23

Connected interface 0 Static route 1 External BGP 20 Internal EIGRP 90 IGRP 100 OSPF 110 IS-IS 115 RIP 120 External EIGRP 170 Internal BGP 200 Unknown 255 (this route will never be used)

Question 24

You can change the ADs of static routes, but by default, they have an AD of 1. That’s only one place above zero, so you can see why a static route’s default AD will always be considered the best by the router.

Answer 24

Okay, the distance vector routing algorithm passes its complete routing table contents to neighboring routers, which then combine the received routing table entries with their own routing tables to complete and update their individual routing tables.

Question 25

the routing table in each router keeps information about three important things: The remote network number The interface that the router will use to send packets to reach that particular network The hop count, or metric, to the network

Answer 25

Remember! Routing convergence time is the time required by protocols to update their forwarding tables after changes have occurred.

Question 26

RIP version 2 provides something called prefix routing and does send subnet mask information with the route updates. Doing this is called classless routing.

Answer 26

RIPv2, unlike RIPv1, is a classless routing protocol (even though it is configured as classful, like RIPv1), which means that it sends subnet mask information along with the route updates.

Question 27

``` RIPv1. Distance vector Maximum hop count of 15 Classful Broadcast based No support for VLSM No authentication. No support for discontiguous networks ```

Answer 27

RIPv2 - Distance vector - Maximum hop count of 15 - Classless - Uses multicast 224.0.0.9 - Supports VLSM networks - Allows for MD5 authentication - Supports discontiguous networks (covered in the next section, “VLSM and Discontiguous Networks”)

Question 28

VLSM Remember, in order to implement a VLSM design on your network, you need to have a routing protocol that sends subnet-mask information with the route updates. This would be RIPv2, EIGRP, or OSPF. RIPv1 and IGRP will not work in classless networks and are considered classful routing protocols.

Answer 28

variable length subnet masks (VLSMs).

Question 29

EIGRP is a classless, enhanced distance vector protocol that possesses a real edge over another older Cisco proprietary protocol, IGRP. That’s basically why it’s called Enhanced IGRP.

Answer 29

EIGRP is referred to as a hybrid routing protocol because it has characteristics of both distance vector and link state protocols.