300-440 Designing and Implementing Cloud Connectivity (ENCC) Questions and Answers

 A fully meshed topology with SD-WAN technology using dynamic routing and prioritized traffic for QoS meets the network architecture requirements of the company. A fully meshed topology provides high availability by eliminating single points of failure and allowing multiple paths between branch offices. SD-WAN technology enables multihoming by supporting multiple transport options, such as MPLS, internet, LTE, etc. SD-WAN also provides QoS by applying policies to prioritize traffic based on application, user, or network conditions. Dynamic routing allows the SD-WAN solution to adapt to changing network conditions and optimize the path selection for each traffic type. A fully meshed topology with SD-WAN technology can also support specific routing needs, such as segment routing, policy-based routing, or application-aware routing. References:

• Designing and Implementing Cloud Connectivity (ENCC) v1.0
• [Cisco SD-WAN Design Guide]
• [Cisco SD-WAN Configuration Guide]

The problem is that the site-list “All-Site” has a higher match sequence than the site-list “Hub”, which means that the policy for “All-Site” will take precedence over the policy for “Hub” for any site that belongs to both lists. This creates a conflict and prevents the engineer from adding a new centralized control policy in Cisco vManage. To resolve this issue, the site-list “All-Site” should be configured with a new match sequence that is lower than the sequence for site-list “Hub”, so that the policy for “Hub” will be applied first and then the policy for “All-Site” will be applied only to the remaining sites that are not in the “Hub” list. References :=

• Designing and Implementing Cloud Connectivity (ENCC, Track 1 of 5), Module 3: Cisco SD-WAN Cloud OnRamp for Colocation, Lesson 3: Cisco SD-WAN Cloud OnRamp for Colocation - Centralized Control Policies
• Cisco SD-WAN Cloud OnRamp for Colocation Deployment Guide, Chapter 4: Configuring Centralized Control Policies
• Cisco SD-WAN Configuration Guide, Release 20.3, Chapter: Centralized Policy Framework, Section: Policy Configuration Overview

An identity mismatch occurs when the local and remote identities configured on the IPsec peers do not match. This can prevent the establishment of an IPsec tunnel or cause traffic to be dropped by the IPsec policy. In this case, the network engineer should verify that the local and remote identities configured on the Cisco WAN edge router and the AWS endpoint match the values expected by each peer. The identities can be an IP address, a fully qualified domain name (FQDN), or a distinguished name (DN). The identities are exchanged during the IKE phase 1 negotiation and are used to authenticate the peers. If the identities do not match, the peers will reject the IKE proposal and the IPsec tunnel will not be established or will be torn down. References :=

• Configure IOS-XE Site-to-Site VPN Connection to Amazon Web Services, Topic: Troubleshooting
• Designing and Implementing Cloud Connectivity (ENCC) v1.0, Module 3: Implementing Cloud Connectivity, Lesson 2: Implementing Cisco SD-WAN Cloud OnRamp for IaaS, Topic: Troubleshooting Cisco SD-WAN Cloud OnRamp for IaaS
• Cisco IOS Security Configuration Guide, Release 15M&T, Chapter: Configuring IPsec Network Security, Topic: Configuring IPsec Identity and Peer Addressing

 BFD (Bidirectional Forwarding Detection) is a protocol that detects failures in the overlay tunnel between Cisco SD-WAN devices. BFD packets are sent and received periodically by each device to check the liveliness and quality of the connection. If a device does not receive a BFD packet from its peer within a specified timeout interval, itconsiders the peer to be unreachable and reports a BFD down event. This event triggers a control connection state change and a possible route change in the SD-WAN fabric.

In this scenario, the engineer discovers that BFD is flapping on vEdge1, which means that the BFD session between vEdge1 and the remote Edge device is going up and down repeatedly. This indicates a connectivity issue between the two devices, such as network congestion, packet loss, or misconfiguration. The most likely cause of the problem is that the remote Edge device failed to respond BFD keepalives within the timeout interval, which resulted in a BFD timeout event on vEdge1. This event caused vEdge1 to mark the remote Edge device as down and notify the control plane. The control plane then tried to establish a new BFD session with the remote Edge device, which may have succeeded or failed depending on the network condition. This cycle of BFD session creation and deletion caused the BFD flapping on vEdge1.

The other options are less likely to be the cause of the problem. Option A is incorrect because if the remote Edge device BFD was down, vEdge1 would not receive any BFD packets from it and would not flap. Option C is incorrect because if the remote Edge device had a duplicate IP address, vEdge1 would not be able to establish a BFD session with it in the first place. Option D is incorrect because the control plane does not delete the BFD session unless there is a configuration change or a port-hop event on the device. References: Bidirectional Forwarding Detection Flap-Reason Definitions on Cisco vEdge Routers, Cisco Catalyst SD-WAN BFD, Cisco SD WAN: BFD (Bidirectional Forwarding Detection)

The correct answer is A and E because they are the IP prefixes that match the tunnel interfaces on the Cisco IOS XE router. The AWS routing options should include the local and remote IP prefixes that are used for the IPsec tunnel endpoints. The other options are either the public IP addresses of the routers or the LAN subnets that are not relevant for the IPsec tunnel configuration. References := Designing and Implementing Cloud Connectivity (ENCC) v1.0, Configure IOS-XE Site-to-Site VPN Connection to Amazon Web Services, Site-to-Site VPN with Amazon Web Services

 Option C is the correct answer because it configures the IKEv2 profile with the correct match identity, authentication, and keyring parameters. It also configures the IPsecprofile with the correct transform set and lifetime parameters. Option A is incorrect because it does not specify the match identity remote address in the IKEv2 profile, which is required to match the AWS virtual private gateway IP address. Option B is incorrect because it does not specify the authentication pre-share in the IKEv2 profile, which is required to authenticate the IKEv2 peers using a pre-shared key. Option C also matches the configuration example provided by AWS1 and Cisco2 for setting up an IKEv2 IPsec site-to-site VPN between a Cisco IOS-XE router and an AWS virtual private gateway. References :=

• 1: AWS VPN Configuration Guide for Cisco IOS-XE
• 2: Configure IOS-XE Site-to-Site VPN Connection to Amazon Web Services

 Cisco SD-WAN IPsec tunnels are different from native IPsec VPN tunnels in several ways. One of the unique features of Cisco SD-WAN IPsec tunnels is that they support real-time dynamic path selection, which means that they can automatically choose the best path for each application based on the network conditions and policies. This feature improves the performance, reliability, and efficiency of the network traffic. Native IPsec VPN tunnels, on the other hand, do not have this capability and rely on static routing or manual configuration to select the path for each tunnel. This can result in suboptimal performance, increased latency, and higher costs. References := Traditional IPsec Versus Cisco SD-WAN IPsec, SD-WAN vs IPsec VPN’s - What’s the difference?, SD-WAN vs. VPN: How Do They Compare?, Traditional IPSEC Versus SD-WAN IPSEC

 A centralized internet gateway is a network design that routes all internet-bound traffic from the on-premises infrastructure through a single point of egress, typically located at the data center or a regional hub1. This approach allows the enterprise to apply consistent security policies and access controls for SaaS applications, as well as optimize the bandwidth utilization and performance of the WAN links2. A centralized internet gateway can use various technologies to provide connectivity to SaaS applications, such as proxy servers, firewalls, web filters, and WAN optimizers3. However, a cloud-based proxy server (option A) is not a part of the centralized internet gateway, but rather a separate service that can be used to route traffic from the on-premises infrastructure to the SaaS provider data center4. VPN connections (option C) and dedicated, private connections (option D) are also not related to the centralized internet gateway, but rather alternative ways of providing secure and reliable access to SaaS applications from the on-premises infrastructure5. Therefore, the correct answer is option B, which describes the basic function of a centralized internet gateway. References := 1: Designing and Implementing Cloud Connectivity (ENCC) v1.0, Module 1: Cloud Connectivity Overview, Lesson 1: Cloud Connectivity Concepts, Topic: Centralized Internet Gateway 2: Cloud OnRamp for SaaS, Cisco IOS XE Catalyst SD-WAN Release 17.3.1a and Later, Topic: Centralized Internet Gateway 3: Architect and optimize your internet traffic with Azure routing preference, Microsoft Azure Blog, Topic: Routing via the premium Microsoft global network 4: What is SaaS? Softwareas a Service, Microsoft Azure, Topic: How SaaS works 5: How an application gateway works, Microsoft Learn, Topic: Application gateway components