Cisco CCNP 300-420 Questions & Answers

• Question 1:

  Refer to the exhibit.

  

  The failover time of ISP-2 is significantly shorter than ISP-1 when an interface on the ISP router toward the campus network fails. Which solution minimizes the downtime to the sub-second?

  A. Aggressive timers

  B. Next-hop address tracking

  C. Graceful-restart

  D. BFD

  Correct Answer: D

  BFD provides sub-second failure detection (https://howdoesinternetwork.com/2018/bfd), and next-hop tracking is enabled in IOS by default (https://www.cisco.com/c/en/us/td/docs/ios/12_2sb/feature/guide/sbbnhop.html) and has a 5 second delay by default. So, I strongly believe it's BFD

• Question 2:

  A customer reports that each time a networking component fails, OSPF recalculates the backup path, with causes a short outage. Which solution must the customer implement to improve this situation?

  A. Aggressive OSPF timers

  B. LFA FRR

  C. Incremental SPF

  D. BFD

  Correct Answer: C

• Question 3:

  A network engineer must design an MSDP multicast solution to provide RP resilience in a network with two separate domains. Also, multicast sources and receivers must register with the local RP. Which solution must the engineer choose?

  A. Configure the RP has value to 0, and traffic will route to the closest RP

  B. Configure the RP loopback interface with the same IP address/32, and traffic will route to the closest RP

  C. Configure the RP group ranges to split the multicast traffic, and traffic will route to the longest match

  D. Configure the RP priority with the same value, and traffic will route to the closest RP

  Correct Answer: B

• Question 4:

  Which design achieves SD-WAN control plane redundancy?

  A. Configuring BFD on the WAN Edge routers

  B. Using multiple instances of vManage in clusters

  C. Deploying using a virtual platform like UCS or CSP

  D. Managing the underlay network with OMP

  Correct Answer: D

  https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/ha-scaling/ios-xe-17/high-availability-book-xe/m-high-availability-and-scaling.html

  Software mechanisms ensure rapid recovery from a failure. To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors the status of all Cisco IOS XE SD-WAN devices in the network and automatically adjusts to changes in the topology as devices join and leave the network. For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD), which runs on the secure IPsec tunnels between routers.

• Question 5:

  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?

  A. Identify the applications with NBAR2 and allocate the required bandwidth accordingly.

  B. Identify the port used by each application and apply a minimum bandwidth guarantee.

  C. Identify the applications and reserve the required bandwidth on the perimeter routers.

  D. Identify the application ports, create groupings, and rate-limit the required bandwidth.

  Correct 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 https://www.cisco.com/c/en/us/products/ios-nx-os-software/network-based-application- recognition-nbar/index.html

• Question 6:

  An architect must design an IPv6 migration solution for a corporation with remote offices to support:

  1.

  The customer has IPv4 peering with their service provider.

  2.

  IPv6 users need access to IPv4 and IPv6 resources.

  3.

  Existing content providers will migrate to IPv6 in the next two years.

  4.

  Users will be migrated in a phase-by-phase approach.

  Which migration solution must the architect choose?

  A. NAT46

  B. tunneling

  C. NAT64

  D. dual-stack

  Correct Answer: D

• Question 7:

  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?

  A. The route reflectors should be made dents of each other.

  B. The route reflectors should be nonclients with regards to each other.

  C. The route reflectors should not have any kind of BGP peering.

  D. The route reflectors should have peering through another nonclient router.

  Correct 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.

• Question 8:

  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?

  A. Provision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers

  B. Enable MSDP between RPs using separate unique loopback interfaces

  C. Enable MSDP between RPs using the configured Anycast RP address

  D. No action is required because PIM registers from the source will, by default, reach each RP

  Correct 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/anyca st.html#wp1029118

  https://www.cisco.com/c/en/us/support/docs/ip/ip-multicast/115011-anycast-pim.html " You need to have a loopback on each prospective RP router, which is different than the loopback that is being used as the RP address."

• Question 9:

  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

  Correct Answer: B

  Explanation: 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.

• Question 10:

  Refer to the exhibit.

  

  An architect must design an IPv6 migration solution for an enterprise customer to support these requirements:

  1.

  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.

  2.

  The service provider will create a client-facing IPv6 interface with a new IPv6 virtual address that points to the same IPv4 DNS server.

  3.

  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.)

  A. Use dual-stack lite from the MPLS network to the IGR.

  B. Use IPv6 tunneling from the devices to the core MPLS network.

  C. Use dual-stack lite from the devices to the core MPLS network.

  D. Use NAT44/64 from the MPLS network to the IGR.

  E. Use NAT44/64 from the devices to the core MPLS network.

  Correct Answer: CD