300-420 practice questions 71–80

1. Question 71 · 359 in bank

   

   Refer to the exhibit. A customer experienced an unexpected network outage when the link between R1 and R2 went down. An architect must design a solution to ensure network continuity in the event the link tails again. Which solution should the design include?

   • AMake R3 an L1L2 router.
   • BMake R31 an L1 router.
   • CMake Area 0 L2-only.
   • DMake R11 an L2 router.

   Show answer

   Answer: A

   Explanation

   answer is correct. ENSLD 300-420 cert guide page 117. When creating a backbone there should never be L1 routers between (L2 only, or) L1/L2 routers.

   Source: Adapted from community discussion — Reinier_veen

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2. Question 72 · 359 in bank

   Select 2

   Which two steps can be taken to improve convergence in an OSPF network? (Choose two.)

   • AUse Bidirectional Forwarding Detection
   • BMerge all the areas into one backbone area
   • CTune OSPF parameters
   • DMake all non-backbone areas stub areas
   • ESpan the same IP network across multiple areas.

   Show answer

   Answer: AC

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3. Question 73 · 359 in bank

   

   Refer to the exhibit. An architect is developing a solution to consolidate networks while retaining device redundancy. The routing protocol for the WAN routers must be open standard, ensure high availability, and provide the fastest convergence time. Which solution must the design include?

   • Aboth routers running EIGRP
   • Bone router running OSPFv2 and other OSPF v3
   • Cone router running ISIS and other OSPF v3
   • Dboth routers running OSPFv2

   Show answer

   Answer: A

   Explanation

   EIGRP is an open standard protocol for years now, Also If we go with Answer B -> How could we guarantee "High availability" of one router is running OSPFv2 (for IPv4) and one running OSPFv3 (for IPv6) ... If one router failes (for example the OSPFv2 one) -> Then the IPv4 traffic would have to go through the OSPFv3 router, but since that is not configured up for IPv4 it would drop the packets. EIGRP has a function called "EIGRP Ipv6" (But that can still be called "EIGRP") So I guess it should be Answer A But shame on Cisco for asking bad questions like these... Its not about knowing the answer, its about seeing into the guys head who wrote the question and try to guess his thoughts.

   Source: Adapted from community discussion — Sickcnt

   References

   • cisco.com documentation

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4. Question 74 · 359 in bank

   

   Refer to the exhibit. An architect is designing a network for a customer supporting a Wake-on-LAN application. Which solution must the architect choose?

   • AIP directed-broadcasts on R1
   • Bspanning-tree uplinkfast on SW1
   • Cspanning-tree uplinkfast on SW2
   • DIP directed-broadcasts on R2

   Show answer

   Answer: D

   Explanation

   As I understand "IP directed broadcast" must be supported on the last router to the destination subnet. Since the sleeping PC's dont have IP adresses, the machines must be calles awake by broadcast that behaves like an unicast untill they reach the destination network. There the directed broadcast is handled like a proper broadcast to wake all WOL machines. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91672-catl3-wol-vlans.html

   Source: Adapted from community discussion — Reinier_veen

   References

   • cisco.com documentation
   • Cisco documentation

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5. Question 75 · 359 in bank

   Select 2

   

   Refer to the exhibit. An architect must design an IPv6 migration solution for an enterprise customer to support these requirements: * Clients will transition to the new IPv6 network, which provides NAT64 and IPv6 DNS resolution services, using the same DNS name that points to the IPv4 address. * The service provider will create a client-facing IPv6 interface with a new IPv6 virtual address that points to the same IPv4 DNS server. * The service provider will support clients that use global IPv6 addresses and encapsulate IPv4 packets into IPv6 tunnels. Which two migration solutions must the architect choose? (Choose two.)

   • AUse dual-stack lite from the MPLS network to the IGR.
   • BUse IPv6 tunneling from the devices to the core MPLS network.
   • CUse dual-stack lite from the devices to the core MPLS network.
   • DUse NAT44/64 from the MPLS network to the IGR.
   • EUse NAT44/64 from the devices to the core MPLS network.

   Show answer

   Answer: BE

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6. Question 76 · 359 in bank

   An engineer is designing an IPv4 addressing plan for an enterprise with 1000 branches. Each branch requires a prefix for data and a prefix for voice. Each prefix must accommodate up to 128 hosts, and prefixes must facilitate summarization at aggregation points in the network. The security team requires a simple method for identifying voce prefixes. Which allocation does the engineer recommend from the RFC1918 address space?

   • A/24 prefixes for data from 10.0.0.0/15 and /24 prefixes for voice from 172.16.0.0/15
   • B/24 prefixes for data from 10.0.0.0/8 and /24 prefixes for voice from the next contiguous /24 prefix per site
   • C/25 prefixes for data from 10.0.0.0/8 end /25 prefixes for voice from the next contiguous /25 prefix per branch
   • D/24 prefixes for data from 10.0.0.0/8 and /24 prefixes for voice from 172.16.0.0/12

   Show answer

   Answer: B

   Explanation

   B is correct For example: Site 0001 Data:10.0.0.0/24 Voice: 10.0.1.0/24 summary route : 10.0.0.0/23 Site 0002 Data:10.0.2.0/24 Voice: 10.0.3.0/24 summary route: 10.0.2.0/23 ....cont... site 0129 Data:10.1.0.0/24 Voice: 10.1.1.0/24 summary route: 10.1.0.0/23 site 0130 Data:10.1.2.0/24 Voice: 10.1.3.0/24 summary route: 10.1.2.0/23 so 3rd octet is odd number assigned to voice, and even number assigned to data; for security team to recongize voice prefix, use an ACL with wildcast to filter odd number on third octet, started from 10.0.1.0 0.0.254.255, 10.1.1.0 0.0.254.255......, 10.1.1.0 0.0.254.255 etc; for 10.0.1.0 0.0.254.255, any IP in binary that started with 00001010.00000000.xxxxxxx1.xxxxxxxx will be matched (x = either 0 or 1), covert 3rd octet into dec, for example, 10000001 = 129 which is a voice VLAN.

   Source: Adapted from community discussion — andrewChan

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7. Question 77 · 359 in bank

   An engineer is designing a PIM Anycast RP solution between two data centers. The design must ensure that RP1 in DC1 and RP2 in DC2 inform each other about specific sources that have joined locally. Which solution must the engineer choose?

   • AProvision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers
   • BEnable MSDP between RPs using separate unique loopback interfaces
   • CEnable MSDP between RPs using the configured Anycast RP address
   • DNo action is required because PIM registers from the source will, by default, reach each RP

   Show answer

   Answer: B

   Explanation

   In Anycast RP, two or more RPs are configured with the same IP address on loopback interfaces. The Anycast RP loopback address should be configured with a 32-bit mask, making it a host address. All the downstream routers should be configured to "know" that the Anycast RP loopback address is the IP address of their local RP. IP routing automatically will select the topologically closest RP for each source and receiver. MSDP used for Anycast RP is an intradomain feature that provides redundancy and load-sharing capabilities. Enterprise customers typically use Anycast RP for configuring a Protocol Independent Multicast sparse mode (PIM-SM) network to meet fault tolerance requirements within a single multicast domain. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html#wp1029118

   Source: Adapted from community discussion — andrewChan

   References

   • Cisco documentation
   • Cisco documentation

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8. Question 78 · 359 in bank

   An engineer is designing a BGP network for a large customer. To permit efficient scaling, the BGP domain is split into clusters. Which peering solution should be used between the route reflectors in different clusters for the BGP routes to be propagated appropriately?

   • AThe route reflectors should be made dents of each other.
   • BThe route reflectors should be nonclients with regards to each other.
   • CThe route reflectors should not have any kind of BGP peering.
   • DThe route reflectors should have peering through another nonclient router.

   Show answer

   Answer: B

   Explanation

   When configure multi-cluster of BGP RRs, RRs should peer with each RR as non-client according to CCIE routing TCP/IP volumn 2 @2001 page 127 - if the route was learned from nonclient IBGP peer, it is reflected to client only (here RR's route learnt from other RRs is able to reflect to its client) - if the route was learned from a client, it is reflected to all nonclients and clients, except for the originating client. (routes learnt within the cluster can reflect to nonclient, RR) - it the route was learnt from an EBGP peer, it is reflected to all nonclients and clients. BTW, bearing in mind that, all RRs should build fully mesh peering.

   Source: Adapted from community discussion — andrewChan

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9. Question 79 · 359 in bank

   An architect must design an IPv6 migration solution for a corporation with remote offices to support: * The customer has IPv4 peering with their service provider. * IPv6 users need access to IPv4 and IPv6 resources. * Existing content providers will migrate to IPv6 in the next two years. * Users will be migrated in a phase-by-phase approach. Which migration solution must the architect choose?

   • ANAT46
   • Btunneling
   • CNAT64
   • Ddual-stack

   Show answer

   Answer: D

   Explanation

   IPv6 users need access to IPv4 and IPv6 resources --> seems like we have Ipv6-only users that need to access to IPv4-only resources... How can they access those resources if not with NAT64?

   Source: Adapted from community discussion — nicolamazzoletti

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10. Question 80 · 359 in bank

    A company uses cloud-based applications for voice and video calls, file sharing, content sharing, and messaging. During business hours, these applications randomly become slow and unresponsive. However, other applications work smoothly with the current applied QoS polices. Which solution must the company choose to resolve the issue?

    • AIdentify the applications with NBAR2 and allocate the required bandwidth accordingly.
    • BIdentify the port used by each application and apply a minimum bandwidth guarantee.
    • CIdentify the applications and reserve the required bandwidth on the perimeter routers.
    • DIdentify the application ports, create groupings, and rate-limit the required bandwidth.

    Show answer

    Answer: A

    Explanation

    using NBAR to identify application and bandwidth usage, then adjust existing QoS polices would be a more simple option. Of course, B is still ok if the network admin know all traffic and bandwidth consumption by other tools, say netflow. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_nbar/configuration/15-mt/qos-nbar-15-mt-book/nbar-protocl-discvry.html#GUID-ED1AEDA1-AE69-45C3-A77E-2AF881CA9C36

    Source: Adapted from community discussion — andrewChan

    References

    • Cisco documentation
    • Cisco documentation

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300-420 practice, question 71. 359 questions available.