https://blogs.damiendye.uk/en/tags/icmp/ Recent content in Icmp on Damien Dye's Blog Hugo en-GB Tue, 01 Sep 2026 08:05:00 +0100 https://blogs.damiendye.uk/en/networking/ping-the-diagnostic-tool-that-opens-a-whole-lot-more/ Tue, 01 Sep 2026 08:05:00 +0100 https://blogs.damiendye.uk/en/networking/ping-the-diagnostic-tool-that-opens-a-whole-lot-more/ Why ping — ICMP echo, not the rest of the protocol — is a liability: a channel every host must answer, so a network that 'only allows ping' has a full VPN out. The threat, who can open one, three tunnels (Hans, icmptunnel, a Python one with AES-128), and the rule that shuts it: nftables, pf, Cisco, Junos, MikroTik and Windows. https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ Fri, 28 Aug 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/how-far-away-is-the-firewall/ A connection that times out tells you nothing about where it died. TTL does. Here is how to count the hops to whatever is eating your port, on Linux, macOS, the BSDs, Solaris and Redox, with a script that needs no root on Linux.