From DALL-E with some prompting
The image provides a detailed explanation of the ‘traceroute’ network diagnostic tool and how it functions, along with potential error messages and their meanings. The ‘traceroute’ command can work with not only ICMP but also TCP/UDP protocols, allowing it to trace the path data packets take through a network to reach the destination. Specifically, the command ‘traceroute -T -p 80 [destination]’ is used to trace the route to the destination over TCP port 80.
The diagram displays several routers (labeled 1, 2, 3, 4) that the traceroute may encounter on its path. Accompanying these are four cases, each illustrating a different error scenario that might occur during the trace:
- Case1: A TCP block might occur, potentially due to a firewall or Access Control List (ACL), indicated by ICMP Type 3, Code 2 (Protocol Unreachable) or Code 10 (Communication with Destination Host is Administratively Prohibited).
- Case2: A block on TCP Port 80 might be encountered, also possibly because of a firewall or ACL.
- Case3: A general TCP block, which might be caused by iptables or similar tools, indicated by ICMP Type 3, Code 2 (Protocol Unreachable) or Code 13 (Communication Administratively Prohibited).
- Case4: A block on TCP Port 80 or a service not being open on the destination, which can result in messages such as “Port Unreachable” or “Connection Refused”.
Each case provides the relevant ICMP message type and code that might be returned if such a situation occurs, which is crucial for network administrators or IT professionals in diagnosing and resolving network connectivity issues.
Lechuck Park 