You configured a site-to-site VPN on your Cisco Firepower NGFW, but the CLI output does not show any IKE SA being established. What would you do as the first troubleshooting step?Verify if IPsec proposal matches on both peers.Check if interesting traffic is reaching the crypto engine using Packet Capture.Check if interesting traffic is reaching the crypto engine using Packet Tracer.Check if interesting traffic is reaching the crypto engine by examining connection events.

The first troubleshooting step you should take if the CLI output does not show any IKE SA being established on your Cisco Firepower NGFW is:

Check if interesting traffic is reaching the crypto engine using Packet Tracer.

Here's why:

1. Packet Tracer is a tool on Cisco devices that allows you to simulate and analyze network traffic. By using Packet Tracer, you can verify if the traffic that should be protected by the VPN (interesting traffic) is actually reaching the crypto engine, which is responsible for encrypting and decrypting the traffic.

2. While verifying if the IPsec proposal matches on both peers is an important step in troubleshooting VPN issues, it's not the first step you should take if no IKE SA is being established. The IKE SA is established before the IPsec SA, so if there's an issue with the IKE SA, it's likely not related to the IPsec proposal.

3. Packet Capture is another tool that can be used to analyze network traffic, but it's not as immediate or interactive as Packet Tracer. It's better suited for capturing and analyzing large amounts of traffic over a period of time.

4. Examining connection events can provide useful information about the traffic flowing through the device, but it's not as direct or specific as using Packet Tracer to check if the interesting traffic is reaching the crypto engine.