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Q1. - (Topic 2)
A switch receives a frame on one of its ports. There is no entry in the MAC address table for the destination MAC address. What will the switch do with the frame?
A. drop the frame
B. forward it out of all ports except the one that received it
C. forward it out of all ports
D. store it until it learns the correct port
Answer: B
Explanation:
Understanding this concept is prime for understanding that when switch receives the data frame from the host not having the MAC address already in the MAC table, it will add the MAC address to the source port on the MAC address table and sends the data frame. If the switch already has the MAC address in its table for the destination, it will forward the frame directly to the destination port. If it was not already in its MAC table, then they frame would have been flooded out all ports except for the port that it came from.
Q2. - (Topic 5)
Including the address on the Routed Ethernet interface, how many hosts can have IP addresses on the LAN to which Routed is connected?
A. 6
B. 30
C. 62
D. 126
Answer: A
Explanation:
This is a /29 address, so there are 6 usable IP’s on this subnet.
Q3. CORRECT TEXT - (Topic 6)
There are three locations in a school district of a large city: ROUTER -M, ROUTER -W and ROUTER -U. The network connection between two of these locations has already functioned. Configure the ROUTER -M router IP addresses on the E0 and S0 interfaces so that the E0 receives the first usable subnet while the S0 receives the second usable subnet from the network 192.168.160.0/28. Both interfaces would receive the last available ip address on the proper subnet.
NotE. The OSPF process must be configured to allow interfaces in specific subnets to participate in the routing process.
Answer: ROUTER-M> enable PassworD. Cisco ROUTER-M# config t ROUTER-M(config)# interface e0 ROUTER-M(config-if)# ip address 192.168.160.14 255.255.255.240
ROUTER-M(config-if)# no shutdown ROUTER -M(config-if)# exit ROUTER -M(config)# interface s0 ROUTER-M(config-if)# ip address 192.168.160.30 255.255.255.240 ROUTER-M(config-if)# no shutdown ROUTER-M(config-if)# end ROUTER-M# copy run start
Q4. - (Topic 3)
Which two of these functions do routers perform on packets? (Choose two.)
A. Examine the Layer 2 headers of inbound packets and use that information to determine the next hops for the packets
B. Update the Layer 2 headers of outbound packets with the MAC addresses of the next hops
C. Examine the Layer 3 headers of inbound packets and use that information to determine the next hops for the packets
D. Examine the Layer 3 headers of inbound packets and use that information to determine the complete paths along which the packets will be routed to their ultimate destinations
E. Update the Layer 3 headers of outbound packets so that the packets are properly directed to valid next hops
F. Update the Layer 3 headers of outbound packets so that the packets are properly directed to their ultimate destinations
Answer: B,C
Explanation:
This is the basic function of the router to receive incoming packets and then forward them to their required destination. This is done by reading layer 3 headers of inbound packets and update the info to layer 2 for further hopping.
Q5. - (Topic 1)
Which OSI layer header contains the address of a destination host that is on another network?
A. application
B. session
C. transport
D. network
E. data link
F. physical
Answer: D
Explanation:
Only network address contains this information. To transmit the packets the sender uses network address and datalink address. But the layer 2 address represents just the address of the next hop device on the way to the sender. It is changed on each hop. Network address remains the same.
Q6. - (Topic 3)
Refer to the exhibit.
The internetwork is using subnets of the address 192.168.1.0 with a subnet mask of
255.255.255.224. The routing protocol in use is RIP version 1. Which address could be assigned to the FastEthernet interface on RouterA?
A. 192.168.1.31
B. 192.168.1.64
C. 192.168.1.127
D. 192.168.1.190
E. 192.168.1.192
Answer: D
Explanation:
Subnet mask 255.255.255.224 with CIDR of /27 which results in 32 hosts per.
192.168.1.31 is the broadcast address for sunbet '0'
192.168.1.64 is the network address for subnet '2'
192.168.1.127 is the broadcast address for subnet '3'
192.168.1.192 is the network address for subnet '6'
Q7. - (Topic 7)
Which network topology allows all traffic to flow through a central hub?
A. bus
B. star
C. mesh
D. ring
Answer: B
Q8. - (Topic 5)
Refer to the exhibit.
The two connected ports on the switch are not turning orange or green. What would be the most effective steps to troubleshoot this physical layer problem? (Choose three.)
A. Ensure that the Ethernet encapsulations match on the interconnected router and switch ports.
B. Ensure that cables A and B are straight-through cables.
C. Ensure cable A is plugged into a trunk port.
D. Ensure the switch has power.
E. Reboot all of the devices.
F. Reseat all cables.
Answer: B,D,F
Explanation:
The ports on the switch are not up indicating it is a layer 1 (physical) problem so we should check cable type, power and how they are plugged in.
Q9. - (Topic 2)
What is the purpose of flow control?
A. To ensure data is retransmitted if an acknowledgement is not received.
B. To reassemble segments in the correct order at the destination device.
C. To provide a means for the receiver to govern the amount of data sent by the sender.
D. To regulate the size of each segment.
Answer: C
Explanation:
Flow control is the management of data flow between computers or devices or between nodes in a network so that the data can be handled at an efficient pace. Too much data arriving before a device can handle it causes data overflow, meaning the data is either lost or must be retransmitted. For serial data transmission locally or in a network, the Xon/Xoff protocol can be used. For modem connections, either Xon/Xoff or CTS/RTS (Clear to Send/Ready to Send) commands can be used to control data flow. In a network, flow control can also be applied by refusing additional device connections until the flow of traffic has subsided.
Reference: http://whatis.techtarget.com/definition/flow-control
Q10. - (Topic 3)
OSPF is configured using default classful addressing. With all routers and interfaces operational, how many networks will be in the routing table of R1 that are indicated to be learned by OSPF?
A. 2
B. 3
C. 4
D. 5
E. 6
F. 7
Answer: C
Explanation:
Although OSPF is configured using default classful addressing but OSPF is a link-state routing protocol so it will always send the subnet mask of each network in their advertised routes. Therefore R1 will learn the the complete subnets. Four networks list below will be in the routing table of R1:+ 172.16.2.64/30+ 172.16.2.228/30+ 172.16.2.232/30+ 172.16.3.0/24 Note: Other networks will be learned as “Directly connected” networks (marked with letter “C”)
Q11. - (Topic 5)
Refer to the exhibit.
For security reasons, information about RTA, including platform and IP addresses, should not be accessible from the Internet. This information should, however, be accessible to devices on the internal networks of RTA.
Which command or series of commands will accomplish these objectives?
A. RTA(config)#no cdp run
B. RTA(config)#no cdp enable
C. RTA(config)#interface s0/0 RTA(config-if)#no cdp run
D. RTA(config)#interface s0/0 RTA(config-if)#no cdp enable
Answer: D
Explanation:
http://www.cisco.com/en/US/tech/tk962/technologies_tech_note09186a00801aa000.shtml# topicenab
When CDP is enabled globally using the cdp run command, it is enabled by default on all supported interfaces (except for Frame Relay multipoint subinterfaces) to send and receive CDP information. You can disable CDP on an interface that supports CDP with the no cdp enable command.
Router#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge S - Switch, H - Host, I - IGMP, r – Repeater
Router# On this router, CDP is enabled on Serial 1 and Ethernet 0 interfaces. Disable CDP on the Serial 1 interface and verify if the neighbor device is discovered on the serial 1 interface, as this output shows: Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface s1 Router(config-if)#no cdp enable Router(config-if)# Z Router#4w5D. %SYS-5-CONFIG_I: Configured from console by console
Q12. - (Topic 1)
Refer to the exhibit.
The output is from a router in a large enterprise. From the output, determine the role of the router.
A. A Core router.
B. The HQ Internet gateway router.
C. The WAN router at the central site.
D. Remote stub router at a remote site.
Answer: D
Explanation:
Since the routing table shows only a single default route using the single interface serial 0/0, we know that this is most likely a remote stub site with a single connection to the rest of the network. All the other answer options would mean that this router would have more connections, and would contain more routes.
Q13. - (Topic 5)
What is the bandwidth on the WAN interface of Router 1?
A. 16 Kbit/sec
B. 32 Kbit/sec
C. 64 Kbit/sec
D. 128 Kbit/sec
E. 512 Kbit/sec
F. 1544 Kbit/sec
Answer: A
Explanation:
Use the “show interface s0/0” to see the bandwidth set at 16 Kbit/sec. The show interface s0/0 command results will look something like this and the bandwidth will be represented by the "BW" on the fourth line as seen below where BW equals 1544 Kbits/sec. R2#show interface serial 0/0 Serial0/0 is up, line protocol is down Hardware is GT96K Serial Internet address is 10.1.1.5/30 MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 uses.
Q14. - (Topic 7)
Under which circumstance should a network administrator implement one-way NAT?
A. when the network must route UDP traffic
B. when traffic that originates outside the network must be routed to internal hosts
C. when traffic that originates inside the network must be routed to internal hosts
D. when the network has few public IP addresses and many private IP addresses require outside access
Answer: B
Explanation: NAT operation is typically transparent to both the internal and external hosts. Typically the internal host is aware of the true IP address and TCP or UDP port of the external host. Typically the NAT device may function as the default gateway for the internal host. However the external host is only aware of the public IP address for the NAT device and the particular port being used to communicate on behalf of a specific internal host.
NAT and TCP/UDP
"Pure NAT", operating on IP alone, may or may not correctly parse protocols that are totally concerned with IP information, such as ICMP, depending on whether the payload is interpreted by a host on the "inside" or "outside" of translation. As soon as the protocol stack is traversed, even with such basic protocols as TCP and UDP, the protocols will break unless NAT takes action beyond the network layer. IP packets have a checksum in each packet header, which provides error detection only for the header. IP datagrams may become fragmented and it is necessary for a NAT to reassemble these fragments to allow correct recalculation of higher-level checksums and correct tracking of which packets belong to which connection. The major transport layer protocols, TCP and UDP, have a checksum that covers all the data they carry, as well as the TCP/UDP header, plus a "pseudo-header" that contains the source and destination IP addresses of the packet carrying the TCP/UDP header. For an originating NAT to pass TCP or UDP successfully, it must recompute the TCP/UDP header checksum based on the translated IP addresses, not the original ones, and put that checksum into the TCP/UDP header of the first packet of the fragmented set of packets. The receiving NAT must recompute the IP checksum on every packet it passes to the destination host, and also recognize and recompute the TCP/UDP header using the retranslated addresses and pseudo-header. This is not a completely solved problem. One solution is for the receiving NAT to reassemble the entire segment and then recompute a checksum calculated across all packets. The originating host may perform Maximum transmission unit (MTU) path discovery to determine the packet size that can be transmitted without fragmentation, and then set the don't fragment (DF) bit in the appropriate packet header field. Of course, this is only a one-way solution, because the responding host can send packets of any size, which may be fragmented before reaching the NAT.
Q15. - (Topic 1)
Which two statements describe the operation of the CSMA/CD access method? (Choose two.)
A. In a CSMA/CD collision domain, multiple stations can successfully transmit data simultaneously.
B. In a CSMA/CD collision domain, stations must wait until the media is not in use before transmitting.
C. The use of hubs to enlarge the size of collision domains is one way to improve the operation of the CSMA/CD access method.
D. After a collision, the station that detected the collision has first priority to resend the lost data.
E. After a collision, all stations run a random backoff algorithm. When the backoff delay period has expired, all stations have equal priority to transmit data.
F. After a collision, all stations involved run an identical backoff algorithm and then synchronize with each other prior to transmitting data.
Answer: B,E
Explanation:
Ethernet networking uses Carrier Sense Multiple Access with Collision Detect (CSMA/CD), a protocol that helps devices share the bandwidth evenly without having two devices transmit at the same time on the network medium. CSMA/CD was created to overcome the problem of those collisions that occur when packets are transmitted simultaneously from different nodes. And trust me, good collision management is crucial, because when a node transmits in a CSMA/CD network, all the other nodes on the network receive and examine that transmission. Only bridges and routers can effectively prevent a transmission from propagating throughout the entire network! So, how does the CSMA/CD protocol work? Like this: when a host wants to transmit over the network, it first checks for the presence of a digital signal on the wire. If all is clear (no other host is transmitting), the host will then proceed with its transmission. But it doesn’t stop there. The transmitting host constantly monitors the wire to make sure no other hosts begin transmitting. If the host detects another signal on the wire, it sends out an extended jam signal that causes all nodes on the segment to stop sending data (think, busy signal). The nodes respond to that jam signal by waiting a while before attempting to transmit again. Backoff algorithms determine when the colliding stations can retransmit. If collisions keep occurring after 15 tries, the nodes attempting to transmit will then time out.