Dns Troubleshooting Scenarios

Scenario: "Sumé": Tied in a Knot

Level: Medium

Type: Fix

Access: Email

Description: A DNS server running Knot DNS is serving the zone sadservers.internal (see ls /var/lib/knot/zones/), but users are reporting that they cannot access blog.sadservers.internal neither api.sadservers.internal. Your task is to diagnose and fix the DNS issues so the services become accessible.
You can manage Knot DNS with sudo knotc commands.

Note: the 203.0.113.0/24 range is part of TEST-NET-3, a block reserved by RFC 5737 for documentation and examples, making it a Bogon IP range.

IMPORTANT. Do not change the Nginx configurations under /opt/services/ for the solution to work.

Test: You are able to access the blog and the API services: curl blog.sadservers.internal returns Welcome to blog.sadservers.internal
curl api.sadservers.internal returns {"status": "ok", "service": "api.sadservers.internal"}

The "Check My Solution" button runs the script /home/admin/agent/check.sh, which you can see and execute.

Time to Solve: 20 minutes.

Scenario: "Jakarta": it's always DNS.

Level: Hard

Type: Fix

Access: Public

Description: Can't ping google.com. It returns ping: google.com: Name or service not known. Expected is being able to resolve the hostname. (Note: currently the VMs can't ping outside so there's no automated check for the solution).

Test: ping google.com should return something like PING google.com (172.217.2.46) 56(84) bytes of data.

Time to Solve: 20 minutes.