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Question 181

Which Cisco VPN architecture uses Virtual Tunnel Interfaces to provide a route-based approach to IPsec VPNs?

1. Policy-based IPsec
2. Route-based IPsec
3. Port Security
4. MACsec

Correct Answer: 2

Explanation

Route-based IPsec VPNs use a logical tunnel interface, commonly called a Virtual Tunnel Interface (VTI), to carry protected traffic. Routing decisions determine which packets are sent through the tunnel rather than relying exclusively on a crypto ACL to identify interesting traffic. This approach can simplify routing designs and support dynamic routing protocols across the VPN tunnel. Policy-based IPsec traditionally uses crypto maps and traffic selectors to determine protected traffic. VTIs therefore provide a more interface-oriented approach to VPN configuration and can make complex routed VPN environments easier to manage.

Question 182

What is the primary purpose of an IPsec Virtual Tunnel Interface (VTI)?

1. Provide a logical interface for routed VPN traffic
2. Assign MAC addresses to switch ports
3. Perform DNS filtering
4. Issue digital certificates

Correct Answer: 1

Explanation

An IPsec Virtual Tunnel Interface provides a logical interface through which routed traffic can be sent into an IPsec VPN tunnel. Because the tunnel behaves similarly to a routed interface, administrators can use routing protocols and routing tables to determine which traffic should traverse the VPN. This differs from traditional policy-based IPsec, where crypto ACLs identify interesting traffic. VTIs can simplify deployments that require dynamic routing or multiple VPN destinations. They do not provide certificate issuance, DNS filtering, or switch-port MAC-address enforcement. Their main role is to provide an interface-based representation of the encrypted VPN path.

Question 183

In a route-based IPsec VPN, which mechanism determines whether traffic should use the VPN tunnel?

1. Routing table
2. DNS cache
3. DHCP binding database
4. MAC address table

Correct Answer: 1

Explanation

In a route-based IPsec VPN, routing determines which traffic is forwarded through the tunnel interface. A route can point a destination network toward a VTI or another logical tunnel interface, allowing normal routing decisions to select the VPN path. This is different from traditional policy-based IPsec, where an access control list associated with a crypto map identifies interesting traffic. DNS caches resolve names, DHCP bindings associate addresses with clients, and MAC address tables are used by switches for Layer 2 forwarding. Route-based VPNs therefore integrate naturally with standard IP routing and can support dynamic routing protocols.

Question 184

Which IKEv2 component is responsible for negotiating cryptographic algorithms and Diffie-Hellman parameters?

1. IKEv2 proposal
2. NHRP resolution
3. Security group tag
4. Access-control rule

Correct Answer: 1

Explanation

An IKEv2 proposal defines the cryptographic algorithms and related parameters that can be used during IKEv2 negotiation. Depending on the platform and configuration, these parameters can include encryption, integrity, and Diffie-Hellman groups. During negotiation, the VPN peers attempt to find a compatible set of parameters. This process establishes the cryptographic foundation for subsequent security associations. NHRP is associated with DMVPN, security group tags are used by Cisco TrustSec, and access-control rules determine permitted traffic. The IKEv2 proposal is therefore a key component of the VPN negotiation process.

Question 185

During IKEv2 negotiation, which exchange establishes the initial IKE security association and performs the Diffie-Hellman exchange?

1. IKE_AUTH
2. CREATE_CHILD_SA
3. IKE_SA_INIT
4. DELETE

Correct Answer: 3

Explanation

IKE_SA_INIT is the first major exchange in IKEv2 negotiation. It is responsible for negotiating initial cryptographic parameters and performing the Diffie-Hellman exchange used to establish shared keying material. The exchange also helps establish the initial IKE security association. IKE_AUTH occurs afterward and authenticates the peers while establishing the first Child SA. CREATE_CHILD_SA is used for creating additional Child SAs or performing rekey operations. DELETE is used when an IKE or Child SA needs to be removed. Understanding the sequence of IKEv2 exchanges is important when troubleshooting VPN establishment problems.

Question 186

Which IKEv2 exchange authenticates the VPN peers and establishes the first Child Security Association?

1. IKE_SA_INIT
2. IKE_AUTH
3. CREATE_CHILD_SA
4. INFORMATIONAL

Correct Answer: 2

Explanation

The IKE_AUTH exchange occurs after IKE_SA_INIT and is responsible for authenticating the VPN peers. It also establishes the first Child Security Association, which is used to protect IPsec data traffic. Authentication can involve methods such as pre-shared keys or digital certificates, depending on the configured policy. IKE_SA_INIT establishes the initial IKE SA and negotiates cryptographic parameters, while CREATE_CHILD_SA is used later for additional Child SAs or rekeying. INFORMATIONAL exchanges can communicate status or control information. Therefore, IKE_AUTH is a critical stage in completing the initial IKEv2 VPN establishment process.

Question 187

Which IKEv2 exchange can be used to create additional Child SAs or rekey existing Child SAs?

1. IKE_AUTH
2. IKE_SA_INIT
3. CREATE_CHILD_SA
4. NHRP Registration

Correct Answer: 3

Explanation

CREATE_CHILD_SA is an IKEv2 exchange used to establish additional Child Security Associations and to perform rekey operations for existing Child SAs. Child SAs protect IPsec data traffic and can have their own negotiated cryptographic parameters. Rekeying allows security associations to be replaced before their lifetime expires, helping maintain secure communication without requiring the entire VPN relationship to be rebuilt from the beginning. IKE_SA_INIT is responsible for initial IKE negotiation, while IKE_AUTH performs authentication and establishes the first Child SA. NHRP Registration belongs to DMVPN rather than IKEv2.

Question 188

What is the main function of a traditional IPsec crypto map?

1. Associate IPsec policy with traffic and a peer
2. Assign DHCP addresses
3. Validate ARP packets
4. Manage certificate revocation

Correct Answer: 1

Explanation

A traditional IPsec crypto map associates VPN security policy with specific traffic and an IPsec peer. The crypto map can reference an access control list that identifies interesting traffic and can define the remote peer and IPsec transform settings. When matching traffic is processed through the interface where the crypto map is applied, the device can initiate or use the appropriate IPsec security association. DHCP addresses, ARP validation, and certificate revocation are handled by different technologies. Crypto maps are therefore a core component of traditional policy-based IPsec configurations.

Question 189

In traditional policy-based IPsec, which configuration element commonly identifies the traffic that should be protected?

1. NHRP map
2. Crypto ACL
3. DHCP pool
4. DNS policy

Correct Answer: 2

Explanation

A crypto ACL is commonly used with traditional policy-based IPsec to identify interesting traffic that should be protected by the VPN. The ACL typically defines source and destination networks or hosts that are permitted to use the IPsec tunnel. When matching traffic is detected, the device uses the associated crypto map and IPsec configuration to protect the packet. NHRP maps are used in DMVPN, DHCP pools provide address assignments, and DNS policies control name-resolution behavior. Crypto ACLs therefore play an important role in determining which traffic enters a traditional policy-based IPsec tunnel.

Question 190

Which configuration approach is generally associated with a route-based VPN rather than a traditional crypto-map VPN?

1. Virtual Tunnel Interface
2. Crypto ACL
3. Interesting traffic ACL
4. Crypto map

Correct Answer: 1

Explanation

A Virtual Tunnel Interface is associated with route-based VPN designs. It creates a logical interface that can participate in routing, allowing the routing table to determine which destinations should use the VPN. This differs from traditional policy-based VPNs, where crypto maps and crypto ACLs identify and protect interesting traffic. Route-based designs are particularly useful when dynamic routing protocols need to operate across VPN tunnels or when administrators want a more interface-oriented configuration. Crypto ACLs and crypto maps remain strongly associated with traditional policy-based IPsec deployments.

Question 191

Which command is commonly useful for verifying active IPsec Security Associations on a Cisco IOS-based device?

1. show ip route
2. show crypto ipsec sa
3. show spanning-tree
4. show vlan brief

Correct Answer: 2

Explanation

The show crypto ipsec sa command is commonly used to inspect active IPsec Security Associations on Cisco IOS-based platforms. It can provide useful information such as peer details, packet counters, encapsulation and decapsulation statistics, and other IPsec-related information. These counters are particularly useful when troubleshooting whether traffic is actually being encrypted and decrypted. show ip route focuses on routing information, show spanning-tree displays Layer 2 spanning-tree information, and show vlan brief displays VLAN information. Therefore, show crypto ipsec sa is an important troubleshooting command for IPsec data-plane verification.

Question 192

Which command is commonly used on Cisco IOS-based devices to inspect IKE security associations?

1. show crypto ikev2 sa
2. show mac address-table
3. show ip dhcp binding
4. show access-lists

Correct Answer: 1

Explanation

The show crypto ikev2 sa command can be used on supported Cisco IOS-based platforms to inspect IKEv2 Security Association information. It can help administrators determine whether an IKEv2 session has been established and examine peer and state information. This is useful when troubleshooting problems where the IPsec tunnel is not coming up or authentication is failing. MAC address tables, DHCP bindings, and access lists provide different types of information and do not directly show the IKEv2 negotiation state. Verification commands are therefore an important part of diagnosing VPN establishment and negotiation problems.

Question 193

When troubleshooting an IPsec VPN, which packet counters can help verify whether encrypted traffic is actually being processed?

1. IPsec encapsulation and decapsulation counters
2. DNS query counters only
3. DHCP lease counters only
4. STP topology counters

Correct Answer: 1

Explanation

IPsec encapsulation and decapsulation counters provide useful evidence about whether protected traffic is being processed by the VPN. Encapsulation counters can indicate packets being encrypted for transmission through the tunnel, while decapsulation counters can indicate packets being received and decrypted. If a VPN is established but counters remain unchanged, administrators may need to investigate routing, ACLs, NAT, or traffic-generation issues. DNS, DHCP, and STP counters address different network functions. Monitoring IPsec packet counters is therefore an effective troubleshooting technique for determining whether the data plane is actually carrying VPN traffic.

Question 194

A site-to-site IPsec tunnel is established, but internal traffic does not pass through it. Which area should be checked first for a routing problem?

1. Routing table
2. Certificate serial number
3. MACsec key lifetime
4. DNS cache

Correct Answer: 1

Explanation

When an IPsec tunnel appears established but application traffic cannot cross it, routing should be checked as one of the fundamental troubleshooting areas. The routing table must contain an appropriate path toward the remote protected network, and return traffic must also have a valid route. In route-based VPNs, the relevant destination route should normally point toward the tunnel interface. Other factors such as ACLs, NAT, security policies, and VPN selectors may also need investigation. Certificate serial numbers, MACsec key lifetimes, and DNS caches do not directly determine whether a routed IPsec tunnel has a valid path to the remote network.

Question 195

What is a common effect of incorrectly translating VPN traffic with NAT?

1. VPN traffic may fail to match the expected IPsec policy
2. IKE automatically becomes RADIUS
3. NHRP creates a certificate
4. ESP changes into DHCP

Correct Answer: 1

Explanation

Incorrect NAT handling can cause VPN traffic to be translated before it reaches the IPsec policy. This may change source or destination addresses so that the traffic no longer matches the expected VPN selectors or crypto ACL. In many site-to-site VPN designs, NAT exemption or an equivalent policy is configured so that traffic destined for the remote protected network is not translated. The exact implementation depends on the platform and design. IKE, RADIUS, NHRP, ESP, and DHCP perform different functions and do not automatically change roles because of NAT configuration.

Question 196

What is the primary purpose of NAT exemption for site-to-site VPN traffic?

1. Prevent specified VPN traffic from being translated
2. Encrypt DNS queries
3. Assign certificates to VPN peers
4. Create NHRP mappings

Correct Answer: 1

Explanation

NAT exemption is commonly used to ensure that traffic between local and remote protected networks is not translated before entering the VPN. If private source addresses are translated unnecessarily, the resulting addresses may no longer match the VPN’s expected traffic selectors or security policy. By excluding VPN traffic from NAT, the original addressing can be preserved for the encrypted communication. The exact configuration varies across Cisco platforms, but the underlying objective is the same: keep specified VPN traffic from undergoing address translation. NAT exemption does not perform encryption, certificate enrollment, or NHRP mapping.

Question 197

Which component of a Cisco FlexVPN architecture commonly provides a centralized configuration model for multiple VPN peers?

1. FlexVPN server
2. DHCP relay
3. DNS resolver
4. Layer 2 switch

Correct Answer: 1

Explanation

FlexVPN can use a hub-and-spoke architecture in which a central FlexVPN server provides services and policy to multiple remote peers. FlexVPN is based on IKEv2 and can use technologies such as Virtual Tunnel Interfaces, dynamic routing, and certificate-based authentication. A centralized design can simplify management when many remote sites need secure connectivity to a central location. DHCP relays, DNS resolvers, and Layer 2 switches perform different networking functions and are not the central VPN architecture component. FlexVPN is designed to provide a flexible, standards-based approach to scalable IKEv2 VPN deployments.

Question 198

Which technology allows a VPN design to use dynamic routing protocols across a logical IPsec tunnel interface?

1. Route-based IPsec with VTI
2. Port Security
3. DHCP Snooping
4. URL Filtering

Correct Answer: 1

Explanation

Route-based IPsec using a Virtual Tunnel Interface allows a VPN to function as a routed logical interface. Because the tunnel interface participates in Layer 3 routing, dynamic routing protocols such as OSPF or EIGRP can potentially operate across the VPN depending on the platform and design. This can simplify large environments where routes change dynamically. Port Security and DHCP Snooping are Layer 2 security features, while URL Filtering controls web destinations. VTI-based route-based IPsec therefore provides a useful foundation for integrating encrypted VPN connectivity with dynamic routing.

Question 199

Which factor can prevent two IKEv2 peers from successfully establishing a VPN if their configured policies do not have a compatible parameter set?

1. Mismatched cryptographic proposals
2. Different switch VLAN names
3. Different DNS search domains
4. Different DHCP lease durations

Correct Answer: 1

Explanation

IKEv2 peers must find compatible cryptographic parameters during negotiation. If the configured proposals do not share an acceptable combination of algorithms or other required parameters, negotiation can fail. For example, incompatible encryption, integrity, or Diffie-Hellman settings may prevent the peers from establishing the required security association. VLAN names, DNS search domains, and DHCP lease durations generally do not determine whether IKEv2 cryptographic negotiation succeeds. When troubleshooting an IKEv2 failure, administrators should therefore compare the relevant proposals and authentication configuration on both peers.

Question 200

Which troubleshooting approach is most useful when an IPsec VPN shows an established IKE session but application traffic still fails?

1. Check only the hostname
2. Check IPsec SAs, routing, NAT, ACLs, and traffic counters
3. Replace all switch VLANs
4. Disable certificate validation permanently

Correct Answer: 2

Explanation

An established IKE session indicates that the VPN control-plane negotiation has progressed, but it does not automatically prove that application traffic is successfully passing through the IPsec data plane. Troubleshooting should therefore include verification of IPsec Security Associations and packet counters, routing toward the remote network, NAT behavior, and relevant ACL or security policies. Traffic selectors and firewall rules may also need to be examined depending on the deployment. Simply checking the hostname or changing VLANs does not address the most likely VPN data-plane problems. A systematic check of these components helps isolate where traffic is being dropped.