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Q41. Refer to the exhibit. 

If OSPF is implemented on the network, which additional configuration is needed to allow traffic from host to host 

A. A virtual link between router 2 and router 4 

B. A virtual link between router 3 and router 4 

C. A virtual link between router 2 and router 3 

D. The current design allows traffic between the two hosts. 



This specific traffic from to would work because this traffic crosses only over the single OSPF area of 

However, traffic from hosts on R4 to R1 would indeed need a virtual link, since area is not connected to the backbone area of 

Q42. Which two statements about proxy ARP are true? (Choose two.) 

A. It is supported on networks without ARP. 

B. It allows machines to spoof packets. 

C. It must be used on a network with the host on a different subnet. 

D. It requires larger ARP tables. 

E. It reduces the amount of ARP traffic. 

Answer: B,D 


Disadvantages of Proxy ARP 

Hosts have no idea of the physical details of their network and assume it to be a flat network in which they can reach any destination simply by sending an ARP request. But using ARP for everything has disadvantages. These are some of the disadvantages: 

It increases the amount of ARP traffic on your segment. 

Hosts need larger ARP tables in order to handle IP-to-MAC address mappings. 

Security can be undermined. A machine can claim to be another in order to intercept packets, an act called "spoofing." 

It does not work for networks that do not use ARP for address resolution. 

It does not generalize to all network topologies. For example, more than one router that connects two physical networks. 

Reference: http://www.cisco.com/c/en/us/support/docs/ip/dynamic-address-allocation-resolution/13718-5.html 

Q43. Refer to the exhibit. 

Which option is the most likely explanation of the duplicate address message logged? 

A. HSRP misconfiguration 

B. a PC with IP of 

C. spanning-tree-loop 

D. a hardware problem 


Q44. Refer to the exhibit. 

Which two statements about the output are true? (Choose two.) 

A. 802.1D spanning tree is being used. 

B. Setting the priority of this switch to 0 for VLAN 1 would cause it to become the new root. 

C. The hello, max-age, and forward delay timers are not set to their default values. 

D. Spanning-tree PortFast is enabled on GigabitEthernet1/1. 

Answer: A,B 


802.1D is the standard for Spanning tree, which is being used here. For priority, The priority order starts from 0 (yes, 0 is valid) and then increases in 4096. 0, 4096, 8192, 12288, …. Etc. 

The lower the number is, the higher is the priority. Here we see that the current root has a priority of 8192, so configuring this with a priority of 0 will make it the new root. 

Q45. Refer to the exhibit. 

If a Layer 3 switch running OSPF in a VRF-lite configuration reports this error, which action can you take to correct the problem? 

A. Set mls cef maximum-routes in the global configuration. 

B. Add the vrf-lite capability to the OSPF configuration. 

C. Upgrade the Layer 3 switch to a model that can support more routes. 

D. Configure the control plane with a larger memory allocation to support the Cisco Express Forwarding Information Base. 


Q46. Which statement about the overload bit in IS-IS is true? 

A. The IS-IS adjacencies on the links for which the overload bit is set are brought down. 

B. Routers running SPF ignore LSPs with the overload bit set and hence avoid blackholing traffic. 

C. A router setting the overload bit becomes unreachable to all other routers in the IS-IS area. 

D. The overload bit in IS-IS is used only for external prefixes. 



The OL bit is used to prevent unintentional blackholing of packets in BGP transit networks. Due to the nature of these protocols, IS-IS and OSPF converge must faster than BGP. Thus there is a possibility that while the IGP has converged, IBGP is still learning the routes. In that case if other IBGP routers start sending traffic towards this IBGP router that has not yet completely converged it will start dropping traffic. This is because it isnt yet aware of the complete BGP routes. OL bit comes handy in such situations. When a new IBGP neighbor is added or a router restarts, the IS-IS OL bit is set. Since directly connected (including loopbacks) addresses on an “overloaded” router are considered by other routers, IBGP can be bought up and can begin exchanging routes. Other routers will not use this router for transit traffic and will route the packets out through an alternate path. Once BGP has converged, the OL bit is cleared and this router can begin forwarding transit traffic. 

Reference: https://routingfreak.wordpress.com/category/ospf-vs-is-is/ 

Q47. What are three benefits of deploying NAT with ALG? (Choose three.) 

A. the use of dynamic ephemeral ports through a firewall 

B. the synchronization of translations between multiple streams of data 

C. the use of deep packet inspection 

D. the use of static ephemeral ports through a firewall 

E. the conversion of session layer addresses from the application payload to outside global addresses 

F. NAT traversal to support asymmetric data sessions 

Answer: A,B,C 

Q48. Which three events can cause a control plane to become overwhelmed? (Choose three.) 

A. a worm attack 

B. processing a stream of jumbo packets 

C. a microburst 

D. a configuration error 

E. a reconvergence failure 

F. a device-generated FTP session 

Answer: A,D,E 

Q49. Which two statements about the OSPF two-way neighbor state are true? (Choose two.) 

A. Each neighbor receives its own router ID in a hello packet from the other neighbor. 

B. Each neighbor receives a hello message from the other neighbor. 

C. It is valid only on NBMA networks. 

D. It is valid only on point-to-point networks. 

E. Each neighbor receives an acknowledgement of its own hello packet from the other neighbor. 

F. Each neighbor receives the router ID of the other neighbor in a hello packet from the other neighbor. 

Answer: A,E 


Drag and drop the multicast protocol definition on the left to the correct default time interval on the right.