Chapter 19: Quiz – DMVPN Tunnels (Answers) CCNPv8 ENARSI

1. Which NHRP message type is sent by a DMVPN spoke to inform the DMVPN hub of NBMA information?

  • registration
  • resolution
  • redirect
  • purge

Explanation: The NHRP registration message allows the DMVPN hub to learn NBMA information from DMVPN spokes.

2. What is a feature of DMVPN Phase 1?

  • support for VPN tunnels only between spoke and hub sites
  • support for spoke-to-spoke communication on a dynamic basis
  • support for spoke-to-spoke communication between DMVPN networks
  • support for next-hop preservation

Explanation: The first DMVPN implementation is Phase 1. In DMVPN Phase 1, VPN tunnels are only created between the spoke and hub sites. This means that traffic between spokes must traverse the hub to reach any other spoke.

3. What are two common problems to avoid when configuring tunnel or overlay networks? (Choose two.)

  • recursive routing
  • outbound interface selection
  • routing loops
  • inbound interface selection
  • split horizon

Explanation: The two problems that are frequently found with tunnel or overlay networks are recursive routing and outbound interface selection.

4. Which DMVPN tunnel state is established first?

  • INTF
  • IKE
  • IPsec
  • NHRP
  • UP

Explanation: There are five DMVPN tunnel states. The order to establishment of the states is as follows: INTF, IKE, IPsec, NHRP, and UP.

5. Which GRE tunnel configuration step is optional?

  • setting the MTU
  • defining the tunnel destination
  • allocating an IP address to the tunnel interface
  • defining the tunnel source

Explanation: For configuring a GRE tunnel, the tunnel IP address, tunnel source, and tunnel destination are required. Configuring the MTU, tunnel bandwidth, and tunnel keepalive are optional.

6. Which NHRP message type is used to locate and provide the tunnel and NBMA IP addresses of the remote spoke?

  • resolution
  • registration
  • redirect
  • purge

Explanation: The NHRP resolution message provides the tunnel IP address and the NBMA IP address of the remote spoke.

7. What type of encapsulation is used by DMVPN?

  • Multipoint GRE (mGRE)
  • Frame Relay
  • 802.1Q
  • PPP

Explanation: DMVPN uses Multipoint GRE (mGRE) for encapsulating packets to be sent over GRE tunnels. The GRE tunnels create an overlay network that is built over an existing transport network.

8. What is the first step for configuring DMVPN on a hub router?

  • Create the tunnel interface.
  • Define the tunnel key.
  • Enable NHRP redirect.
  • Define the MTU for the tunnel.

Explanation: The first step in configuring DMVPN on a hub router is to configure the tunnel interface. Once the interface is configured, the tunnel key, redirects, MTU size, and other properties can be configured.

9. What is the recommended holdtime for valid NHRP mapping entries in the NHRP cache?

  • 30 seconds
  • 600 seconds
  • 7200 seconds
  • 65,535 seconds

Explanation: NHRP entries in the NHRP cache stay valid for 7200 seconds by default. This holdtime can be modified using the ip nhrp holdtime command. It is recommend the holdtime for valid entries be modified to 600 seconds.

10. Which NHRP message extension contains a list of the next-hop servers that NHRP request packets have traversed?

  • forward transit NHS record
  • reverse transit NHS record
  • responder address
  • authentication

Explanation: The forward transit NHS record contains a list of next-hop servers (NHSs) that NHRP request packets have traversed.

11. A network administrator notices that a DMVPN tunnel is not fully established and has not moved beyond the NHRP tunnel state. What is indicated by the NHRP state?

  • The DMVPN spoke router has not registered.
  • The line protocol of the DMVPN tunnel is down.
  • IPsec tunnels have not established IKE sessions.
  • IPsec security associations are not established.

Explanation: The NHRP state indicates that the DMVPN spoke router has not registered. Once the spoke router registers, the interface will move into the “UP” state.

12. For configuring IPv6 DMVPN, which IP version is supported as the transport and tunnel protocol?

  • Only IPv4 is supported as the transport protocol.
  • Only IPv6 is supported as the tunnel protocol.
  • Only IPv4 is supported as the tunnel protocol.
  • Both IPv4 and IPV6 are supported as either the tunnel protocol or the transport protocol.

Explanation: DMVPN supports the use of both IPv4 and IPv6 as either the tunnel protocol or the transport protocol in any combination required.


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