B. The remote Edgedevice failed to respond BFD keepalives.

Answer DescriptionExplanation:
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, it considers 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.

D. A centralized data policy must be configured

Answer DescriptionExplanation: A centralized data policy is a policy that is applied to all devices in the overlay network, regardless of the site list. A localized data policy is a policy that is applied only to the devices that are listed in the site list. In this case, the network engineer wants to apply the policy to all devices in the overlay network, not just the specific devices in the site list. Therefore, a centralized data policy must be configured on the on-premises Cisco WAN edge router.

C. redistribute ospf 1 match external

Answer DescriptionExplanation: The command redistribute ospf 1 match external is missing on router R2. This command is needed to redistribute only the external OSPF routes into BGP. The external OSPF routes are those that are learned from another routing protocol or redistributed into OSPF. In this case, the 10.0.10.0/24 network is an external OSPF route, as it is redistributed from EIGRP into OSPF on router R1. The other commands are either already present or not relevant for this scenario.

B. Enable bgp advertisement

Answer DescriptionExplanation: To enable the OMP advertisement of BGP routes for a specific VRF instance on a Cisco IOS XE SD-WAN device, the engineer must first configure the global address-family ipv4 and then enable bgp advertisement under the vrf definition. This will allow the device to advertise the BGP routes learned from the cloud provider to the OMP control plane, which will then distribute them to the other SD-WAN devices in the overlay network.

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B. Check the security group rules for the host VPC.
C. Check the IPsec SA counters.

Answer DescriptionExplanation: The end-to-end ping between the office user PC and the AWS EC2 instance is not working because either the security group rules for the host VPC are blocking the ICMP traffic or the IPsec SA counters are showing errors or drops. To diagnose the loss of connectivity, the engineer should check both the security group rules and the IPsec SA counters. The network security group rules on the host VNET are not relevant because they apply to Azure, not AWS. The IPsec SA configuration on the Cisco VPN router and the AWS private virtual gateway are not likely to be the cause of the problem because the site-to-site VPN tunnel is already up and the site-to-site routing works correctly.

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Answer Description