Cisco Exam #642-801: BSCI Exam (MeasureUp)
Practice your advanced IP addressing and routing skills in implementing scalability for Cisco routers for your CCNP, CCDP or CCIP with these nine sample questions.
courtesy of MeasureUp
Question:
1. Which default metrics do both the Interior Gateway Routing Protocol (IGRP) and Enhanced Interior Gateway Routing Protocol (EIGRP) routing protocols use?
a. Bandwidth and delay
b. Cost and delay
c. Cost and metric
d. Cost and hop count
e. Metric and delay
2. Which addresses can be summarized by the following command: area 3 range 172.16.32.0 255.255.224.0 ? (Choose two.)
a. 172.16.33.14
b. 172.16.15.14
c. 172.16.62.0
d. 172.16.65.0
e. 172.16.66.0
3. OSPF uses the _____________ algorithm to calculate the lowest cost path to a destination network.
a. Dijkstra
b. DUAL
c. Diffie-Hellman
d. Bellman Ford
4. Which statements are true concerning Open Shortest Path First (OSPF)? (Choose two.)
a. Type 2 Link-State Advertisements (LSAs) are flooded within the confines of their area.
b. Autonomous System Boundary Routers (ASBRs) generate Type 7 and Type 5 Link-State Advertisements (LSAs) (depending on to whom who they are connected).
c. Type 2 Link-State Advertisements (LSAs) are flooded by Border Gateway Protocol (BGP).
d. Type 2 Link-State Advertisements (LSAs) are flooded by Autonomous System Boundary Routers (ASBRs).
e. Autonomous System Boundary Routers (ASBRs) generate Type 1 and Type 2 Link-State Advertisements (LSAs) (depending on to whom they are connected).
5. What does the "1" stand for in the command "router ospf 1"?
a. Open Shortest Path First (OSPF) routing protocol instance number 1
b. Open Shortest Path First (OSPF) routing protocol instance for area 1
c. Open Shortest Path First (OSPF) routing protocol instance for Autonomous System Boundary Router (ASBR) number 1
d. Open Shortest Path First (OSPF) router ID number 1
6. What are typically found in an Open Shortest Path First (OSPF) "hello" packet? (Choose two.)
a. Router ID
b. Router Type
c. Neighbor Information
d. Route Reflector Names
e. Autonomous Border Router (ABR) and Autonomous System Boundary Router (ASBR) Addresses
7. What is the main difference between Routing Information Protocol (RIP) and Open Shortest Path First (OSPF)?
a. Both are Interior Gateway Protocols (IGPs), but the Routing Information Protocol (RIP) convergence time is much shorter than that of Open Shortest Path First (OSPF).
b. Routing Information Protocol (RIP) is a distance vector protocol, whereas Open Shortest Path First (OSPF) is a Link-State protocol.
c. Open Shortest Path First (OSPF) allows for a lower hop count than Routing Information Protocol (RIP).
d. Routing Information Protocol (RIP) works better in large internetworks than Open Shortest Path First (OSPF).
8. On which layer of the OSI model does a Web browser operate?
a. Application Layer
b. Presentation Layer
c. Session Layer
d. Network Layer
9. You need to configure an Intermediate System-to-Intermediate System (IS-IS) nonbroadcast multiaccess (NBMA) link using the x.25 protocol.
How does Cisco recommend you configure the link?
a. As an NBMA link
b. As a point-to-point link
c. As a broadcast link
d. As a Level-1 link
1. A is correct. EIGRP and IGRP use both "bandwidth" and "delay" as their routing metrics. EIGRP uses the same formula and concept, except that the actual values are 32 times that of IGRP. This enables greater granularity for the EIGRP routing protocol.
EIGRP and IGRP both have the following metrics for path selection:
- Bandwidth
- Delay
- Load (Disabled by Default)
- Reliability (Disabled by Default)
- Maximum Transfer Unit (MTU) (Disabled by Default)
- Hop Count (Disabled by Default)
Some of the metric components that you see above are disabled by default. Their values are observed and recorded, but they are not used in the final calculations. Enabling "load," "reliability," and "MTU" can have an undesirable effect on the network and make it unstable. If you enabled the "load" metric, as soon as one link is overwhelmed, EIGRP switches all traffic to an alternate path. When the new path is overwhelmed, EIGRP reverts all the traffic back to the original path. This path switching would occur as soon as the link became saturated with traffic.
Cost is the metric used by OSPF.
2. A and C are correct. For an address to be summarized into one statement, all addresses must share common high priority bits. In this case, you are looking for addresses that have the same most significant 19 bits. It is a simple process of examination of the first 16 bits. The third octet will take a closer examination.
Look at the bit patterns and notice which two addresses are the same up to a certain point. (Starting from the left instead of the right.)
128 64 32 16 8 4 2 1
15 0 0 0 0 1 1 1 1
33 0 0 1 0 0 0 0 1
62 0 0 1 1 1 1 1 0
65 0 1 0 0 0 0 0 1
66 0 1 0 0 0 0 1 0
The .15 address has a "00001111" pattern, which is not similar to any other patterns you see.
The .33 address has a "00100001" pattern, which is similar to the .62 pattern.
The .62 address has a "00111110" pattern, which is similar to the .33 pattern.
The .65 address has a "01000001" pattern, which is not similar to any other patterns you see.
Notice that the bit patterns in .33 and .62 are the same all the way to the 3rd bit (from the left). This is what will determine whether or not a group of addresses can be summarized. The addresses with the same significant bit patterns can be summarized.
3. A is correct. The Dijkstra algorithm is what OSPF uses to calculate the cost to a destination network. It adds the cost of all the possible paths to a destination network and selects the path with the lowest overall cost.
The Diffie-Hellman algorithm is used for data encryption.
The Bellman Ford algorithm is used by distance vector routing protocols, such as Routing Information Protocol (RIP).
The DUAL algorithm is used by EIGRP.
4. A and B are correct. Area Border Routers (ABRs) generate Type 3 or 4 LSAs. Type 3/4 LSAs describe the links between the ABRs and the routers within the area.
ASBRs generate Type 5 LSAs in an AS and Type 7 in an NSSA (Not so stubby area). Type 5 LSAs indicate the routes that are external to the AS.
Designater Routers (DRs) generate Type 2 LSAs (network link entries), which are flooded within the confines of the particular area. They list all the routers within a particular area.
Internal Routers generate Type 1 LSAs, which describe the status of the router's participation in the area.
5. A is correct. The "1" in "router ospf 1" command tells the router to start an instance of the OSPF routing protocol and give it the number "1". When you enter the "network" command to announce your networks and assign area IDs, you associate those networks with this instance of the OSPF routing protocol. See the example below:
router (config)# router ospf 1
router (config-router)# network 1.4.0.0 0.0.0.255 area 0
These commands tell the router to start an OSPF routing protocol process called "1" and associate the following network information with that process number.
If you need a separate instance of OSPF running on the same router, you can issue the following command:
router (config)# router ospf 2
router (config-router)# network 1.5.0.0 0.0.0.255 area 1
These commands associate network "1.5.0.0" with OSPF process 2.
The benefit of having this type of system is that you can restart the OSPF 2 process without affecting OSPF 1.
6. A and C are correct. The OSPF "hello" packet contains the following Post Designated Router (DR) and Backup Designated Router (BDR) Election information :
- Router ID
- Hello and Dead intervals
- Neighbors
- Area ID
- Router Priority
- DR and BDR Addresses
- Authentication Password
- Stub Area Flag
Routing protocols that use only event-triggered updates must have a mechanism that will "tell" neighbors that they are still available. The "hello" packet accomplishes this task.
Distance vector routing protocols like IP Routing Information Protocol (RIP) communicate their routing tables periodically; there is no need to say hello.
EIGRP and OSPF enabled routers send out "hello" packets on multicast addresses (EIGRP on 224.0.0.10 and OSPF on 224.0.0.5) in an effort to establish adjacencies with neighbors. Establishing this neighbor relationship only occurs within the same Autonomous System (AS).
7. B is correct. To distinguish between distance vector and Link-State routing protocols, users should answer the following three questions:
- What does the routing protocol talk?
- When does the routing protocol talk?
- To whom does the routing protocol talk?
Distance Vector protocols broadcast their entire routing table to directly-connected neighbors. In a distance vector routing protocol, if the hop count exceeds 15 hops, or the TTL (Time to Live) counter reaches zero, the frame is discarded. The maximum hop count method is known as "Counting to Infinity."
Link-State protocols broadcast the state of the link to all neighbors when the state of the link changes. Link-State routing protocols have the following characteristics:
- They build and maintain a database of the network topology.
- The database is built from the information learned via Link-State Packets (LSPs).
- They only send incremental topology updates.
- They rely on the Shortest Path First (SPF) algorithm to analyze routing updates.
- They allow the creation of larger hierarchical network topologies.
- They support classless addressing.
- They allow route summarization.
8. A is correct. The Application layer is the layer at which applications, such as Web browsers, operate. It is the highest layer of the OSI model and is the one which users directly interact.
The Presentation layer is responsible for defining data formats, such as ASCII text and JPEG formats.
The Session layer defines the initialization, termination, and controls conversations.
The Network layer is part of the OSI model and resides between the Data-Link and Transport layers. It controls packets and is where the Internet Protocol (IP) functions.
9. B is correct. Cisco recommends configuring adjacencies in an NBMA IS-IS environment as a point-to-point link. This is due to the fact that NBMA configurations in this environment complicate the configuration and introduce the possibility of many more errors.
A point-to-point link is used to connect two routers. In IS-IS, the routers become neighbors after successfully exchanging hello packets. Once this occurs, the neighbors send their complete sequence number packet (CSNP) list of their link-state database. Synchronization takes place after the transmission of the CSNPs.
On broadcast links, the Designated Intermediate System (DIS) sends packets to the other routers on the network to minimize traffic and build the routing table database. The DIS floods the link-state packets (LSPs) to all the routers. The DIS maintains the adjacencies for the network.
An NBMA link is a combination of a broadcast link and a point-to-point link. NBMA environments use permanent virtual circuits (PVCs) to provide connectivity to neighbors.
Level-1 routers are intra area routers and do not provide links for IS-IS. They keep routes for internal areas.
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