ActualTests.Cisco.640-802.Exam.Q.and.A.08.15.08-DDU (1130589), страница 9
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Examine the age of the packet.The router must ensure that the packet has not come too far to be forwarded. Forexample, IPX headers contain a hop count. By default, 15 hops is the maximum numberof hops (or routers) that a packet can cross. If a packet has a hop count of 15, the routerdiscards the packet.IP headers contain a Time to Live (TTL) value.
Unlike the IPX hop count, whichincrements as the packet is forwarded through each router, the IP TTL value decrementsas the IP packet is forwarded through each router. If an IP packet has a TTL value of 1,the router discards the packet. A router cannot decrement the TTL value to 1 and thenforward the packet.3. Determine the route to the destination. Routers maintain a routing table that listsavailable networks, the direction to the desired network (the outgoing interface number),and the distance to those networks. After determining which direction to forward thepacket, the router must build a new header.
(If you want to read the IP routing tables on aWindows 95/98 workstation, type ROUTE PRINT in the DOS box.)4. Build the new MAC header and forward the packet. Finally, the router builds anew MAC header for the packet. The MAC header includes the router's MAC addressand the final destination's MAC address or the MAC address of the next router in thepath.Figure 5 shows the contents of a packet before and after it has been forwarded by arouter. Figure 5 also shows the contents of the router's routing tables.Figure 5: Routers forward packets based on the network address.QUESTION 73:The Certkiller network is displayed in the diagram shown below:The Certkiller network consists of a small office with twenty-five employees that hasone connection to the Internet through the CK1 router.
What routing configurationsare recommended on the CK1 and ISP routers?A. BGP on both the routers.B. RIP on both the routers.C. Default routes on both routers.Actualtests.com - The Power of Knowing640-802D. BGP on the ISP router and a static route on CK1 .E. A default route on CK1 and a static route on the ISP router.F. None of the aboveAnswer: EExplanation:Since private network use RFC 1918 IP address ranges internally, and because ofsecurity reasons, it is generally not possible to use an interior routing protocol with theISP. This eliminates choice B.
When connecting to an ISP, usually only BGP or staticroutes are supported. In this case, since there is only one connection to the Internet, BGPis not needed so choices A and D can be eliminated. A static default route would beneeded on router CK1 to route to the Internet.
In turn, the ISP only needs a specific staticroute to reach the LAN of the Certkiller network.Incorrect Answers:A, D: BGP is not needed on networks that contain only a single link to the Internet.B. Interior routing protocols are generally not supported with an ISP.C.
A default route on the ISP router would send all of their customers Internet traffic tothe Certkiller network, and not the Internet.QUESTION 74:A new point to point circuit is installed, connecting Certkiller 1 to Certkiller 2 asshown below:Users at Certkiller 1 wish to utilize the existing Internet connection at Certkiller 2. Todo this, a gateway of last resort needs to be set. What is the command to do this?A. Certkiller 1(config)# ip route 172.16.4.2 0.0.0.0 0.0.0.0B. Certkiller 1(config)# ip route 0.0.0.0 0.0.0.0 S1C.
Certkiller 1(config)# ip route 172.16.4.1 0.0.0.0 0.0.0.0D. Certkiller 1(config)# ip route S0 0.0.0.0 0.0.0.0E. Certkiller 1(config)# ip route 0.0.0.0 0.0.0.0 172.16.4.2F. None of the aboveAnswer: EExplanation:Setting the default gateway is done by issuing either the "ip route 0.0.0.0 0.0.0.0 serial 0"or the "ip route 0.0.0.0 0.0.0.0 172.16.4.2" command.
The following excerpt providesActualtests.com - The Power of Knowing640-802some additional information:Incorrect Answers:A, C. The IP address of the next hop needs to go after the route, not before.B. This would have been acceptable if the interface specified was S0, not S1.C. The interface used to forward packets for the route should be placed after the route,not before.QUESTION 75:The network associate is configuring OSPF on the Core router shown below. All theconnections to the branches should be participating in OSPF. The link to the ISPshould NOT participate in OSPF and should only be advertised as the default route.What set of commands will properly configure the Core router?A.
Core(config-router)# default-information originateCore(config-router)# network 10.0.0.0 0.255.255.255 area 0Core(config-router)# exitCore(config)# ip route 0.0.0.00.0.0.010.10.2.14B. Core(config-router)# default-information originateCore(config-router)# network 10.10.2.32 0.0.0.31 area 0Core(config-router)# exitCore(config)# ip route 0.0.0.00.0.0.0 10.10.2.14C.
Core(config-router)# default-information originateCore(config-router)# network 10.10.2.13 0.0.0.242 area 0Core(config-router)# exitCore(config)# ip route 0.0.0.00.0.0.010.10.2.14D. Core(config-router)# default-information originateCore(config-router)# network 10.10.2.16 0.0.0.15 area 0Core(config-router)# exitCore(config)# ip route 0.0.0.00.0.0.010.10.2.14Actualtests.com - The Power of Knowing640-802Answer: DExplanation:There are two ways to inject a default route into a normal area.1. If the ASBR already has the default route in its routing table, you can advertise theexisting 0.0.0.0/0 into the OSPF domain with the default-information originate routerconfiguration command.2. If the ASBR doesn't have a default route, you can add the keyword always to thedefault-information originate command (default-information originate always).This command will advertise a default route into the OSPF domain, regardless of whetherit has a route to 0.0.0.0.
Another benefit of adding always keyword is that it can addstability to the internetwork. For example, if the ASBR is learning a default route fromanother routing domain such as RIP and this route is flapping, then without the alwayskeyword, each time the route flaps, the ASBR will send a new Type 5 LSA into theOSPF domain causing some instability inside the OSPF domain.
With the alwayskeyword, the ASBR will advertise the default inside the OSPF domain always, and thusthe flapping of the default route from the RIP domain will not cause any instability insidethe OSPF domain.In the example shown here, only choice D is correct as the wildcard mask correctlyspecifies the 10.10.2.16 0.0.0.15 networks, which include all IP addresses in the10.10.2.16-10.10.2.31 range. In this question we were told that the ISP link should NOTbe configured for OSPF, making choice A incorrect.Reference: http://www.cisco.com/warp/public/104/21.htmlQUESTION 76:A new Internet T1 is being added to the Certkiller network as shown:Actualtests.com - The Power of Knowing640-802The ISP assigned you the class CIP address 207.134.6.0/30 for this Internetconnection.
A default route to the Internet should be set up. Which of the followingare acceptable ways to configure this on the Gateway router? (Select all that apply)A. Gateway(config)# ip route 0.0.0.0 0.0.0.0 207.134.6.1.B. Gateway(config)# router ripGateway(config-router)# network 207.134.6.0 defaultC. Gateway(config)# ip route 207.134.6.0 255.255.255.0 Serial0/0D. Gateway(config)# router OSPFGateway(config-router)# network 207.134.6.0E.
Gateway(config)# ip default-network 207.134.6.0Answer: A, EExplanation:This question only involves the configuration of the gateway router to the ISP, nothingelse. You have two choices to accomplish this: the command "ip route" or the command"ip default-network". Both of these methods will configure a default route to the ISP asdesired.Incorrect Answers:B, D: RIP and OSPF are interior routing protocols. The T1 Internet connection that isbeing set up here is between two different Autonomous Systems. The only routingprotocol that could be potentially used is BGP, but that is not an option.C: This command will only set up a static route to the 207.134.6.0/24 network. We wishto set up a static default route.Actualtests.com - The Power of Knowing640-802QUESTION 77:Router Certkiller 2 is connected to an ISP as shown below:In the ISP link to the WAN shown above, you must complete the connectionbetween the Certkiller 2 router to the service provider.
To accomplish this task,which two devices could be installed at the Certkiller site to provide a connectionthrough the local loop to the CO of the provider? (Choose two)A. MultiplexerB. WAN switchC. ATM switchD. CSU/DSUE. PVCF. ModemG. LMIAnswer: D, FQUESTION 78:Part of the Certkiller network is shown below:Study the exhibit shown above. A problem with network connectivity has beenobserved. It is suspected that the cable connected to switch port Fa0/9 on SwitchCertkiller 1 is disconnected.
What would be an effect of this cable beingdisconnected?A. Communication between VLAN3 and the other VLANs would be disabledB. Host Certkiller B would not be able to access the server in VLAN9 until the cable isreconnectedC. For less than a minute, Host Certkiller B would not be able to access the server inVLAN9. Then normal network function would resumeD. The transfer of files from Host Certkiller B to the server in VLAN9 would beActualtests.com - The Power of Knowing640-802significantly slowerE.
None of the aboveAnswer: CExplanation:Spanning-Tree Protocol (STP) is a Layer 2 protocol that utilizes a special-purposealgorithm to discover physical loops in a network and effect a logical loop-free topology.STP creates a loop-free tree structure consisting of leaves and branches that span theentire Layer 2 network. The actual mechanics of how bridges communicate and how theSTP algorithm works will be discussed at length in the following topics. Note that theterms bridge and switch are used interchangeably when discussing STP. In addition,unless otherwise indicated, connections between switches are assumed to be trunks.STP keeps the port either in block or in forward states, when forward port disconnectthen within the less then a minute blocked port comes into forward state so packets startsto go through new forward port.The Spanning Tree Protocol (STP) would identify the best path as well as alternate pathto reach in proper destination.
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