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Q1. - (Topic 1)
Which two characteristics apply to Layer 2 switches? (Choose two.)
A. Increases the number of collision domains
B. Decreases the number of collision domains
C. Implements VLAN
D. Decreases the number of broadcast domains
E. Uses the IP address to make decisions for forwarding data packets
Answer: A,C
Explanation:
Layer 2 switches offer a number of benefits to hubs, such as the use of VLANs and each switch port is in its own separate collision domain, thus eliminating collisions on the segment.
Q2. - (Topic 1)
Which layer of the OSI model controls the reliability of communications between network devices using flow control, sequencing and acknowledgments?
A. Physical
B. Data-link
C. Transport
D. Network
Answer: C
Q3. - (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.
Q4. - (Topic 5)
Which two of the following are true regarding the configuration of RouterA? (Choose two.)
A. At least 5 simultaneous remote connections are possible
B. Only telnet protocol connections to RouterA are supported C. Remote connections to RouterA using telnet will succeed
D. Console line connections will nevertime out due to inactivity
E. Since DHCP is not used on Fa0/1 there is not a need to use the NAT protocol
Answer: A,C
Q5. - (Topic 1)
Which statements are true regarding ICMP packets? (Choose two.)
A. They acknowledge receipt of TCP segments.
B. They guarantee datagram delivery.
C. TRACERT uses ICMP packets.
D. They are encapsulated within IP datagrams.
E. They are encapsulated within UDP datagrams.
Answer: C,D
Explanation:
Ping may be used to find out whether the local machines are connected to the network or whether a remote site is reachable. This tool is a common network tool for determining the network connectivity, which uses ICMP protocol instead of TCP/IP and UDP/IP. This protocol is usually associated with the network management tools, which provide network information to network administrators, such as ping and traceroute (the later also uses the UDP/IP protocol). ICMP is quite different from the TCP/IP and UDP/IP protocols. No source and destination ports are included in its packets. Therefore, usual packet-filtering rules for TCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as the packet’s Message type is included for denoting the purposes of the ICMP packet. Most commonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echo reply, destination unreachable, source quench, redirect, echo request, time exceeded, and parameter problem respectively. In the ping service, after receiving the ICMP "echo request" packet from the source location, the destination
Q6. - (Topic 5)
Refer to the exhibit.
A technician pastes the configurations in the exhibit into the two new routers shown. Otherwise, the routers are configured with their default configurations.
A ping from Host1 to Host 2 fails, but the technician is able to ping the S0/0 interface of R2 from Host 1. The configurations of the hosts have been verified as correct. What could be the cause of the problem?
A. The serial cable on R1 needs to be replaced.
B. The interfaces on R2 are not configured properly
C. R1 has no route to the 192.168.1.128 network.
D. The IP addressing scheme has overlapping subnetworks.
E. The ip subnet-zero command must be configured on both routers.
Answer: C
Explanation:
Without a static route pointing to the host 2 network the router R1 is unaware of the path to take to reach that network and reply traffic cannot be sent.
Q7. - (Topic 3)
Which address are OSPF hello packets addressed to on point-to-point networks?
A. 224.0.0.5
B. 172.16.0.1
C. 192.168.0.5
D. 223.0.0.1
E. 254.255.255.255
Answer: A
Explanation:
Why does the show ip ospf neighbor Command Reveal Neighbors in the Init State? http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080093f11.shtml OSPF hello packets have a destination address of 224.0.0.5 (the all ospf routers multicast
address).
Q8. - (Topic 7)
Which routing protocol has the smallest default administrative distance?
A. IBGP
B. OSPF
C. IS-IS
D. EIGRP
E. RIP
Answer: D
Explanation: http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/15986-admin-distance.html Default Distance Value TableThis table lists the administrative distance default values of the protocols that Cisco supports:
Route Source Default Distance Values
Connected interface 0 Static route 1 Enhanced Interior Gateway Routing Protocol (EIGRP) summary route 5 External Border Gateway Protocol (BGP) 20 Internal EIGRP 90 IGRP 100 OSPF 110 Intermediate System-to-Intermediate System (IS-IS) 115 Routing Information Protocol (RIP) 120 Exterior Gateway Protocol (EGP) 140 On Demand Routing (ODR) 160 External EIGRP 170 Internal BGP 200 Unknown*
Q9. - (Topic 3)
Refer to the exhibit.
PC1 pings PC2. What three things will CORE router do with the data that is received from PC1? (Choose three.)
A. The data frames will be forwarded out interface FastEthernet0/1 of CORE router.
B. The data frames will be forwarded out interface FastEthernet1/0 of CORE router.
C. CORE router will replace the destination IP address of the packets with the IP address of PC2.
D. CORE router will replace the MAC address of PC2 in the destination MAC address of the frames.
E. CORE router will put the IP address of the forwarding FastEthernet interface in the place of the source IP address in the packets.
F. CORE router will put the MAC address of the forwarding FastEthernet interface in the place of the source MAC address.
Answer: B,D,F
Explanation:
The router will forward the frames out the interface toward the destination – B is correct. Since the router will has the end station already in it’s MAC table as see by the “show arp” command, it will replace the destination MAC address to that of PC2 – D is correct. The router will then replace the source IP address to 172.16.40.1 – E is correct.
Q10. - (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.