https://blogs.damiendye.uk/en/tags/vpn/ Recent content in Vpn on Damien Dye's Blog Hugo en-GB Mon, 14 Sep 2026 15:00:00 +0100 https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ Mon, 14 Sep 2026 15:00:00 +0100 https://blogs.damiendye.uk/en/networking/a-vpn-out-of-parts-and-what-egress-really-is/ A VPN is a virtual link plus a carrier, and Linux ships a program for each: pppd or a tap device, and netcat. Building it both ways — over TCP, UDP, TLS and DTLS, with zstd compression — shows what a VPN is made of, and what egress really is: once an attacker has root and outbound is open, the tunnel is already installed. https://blogs.damiendye.uk/en/networking/ipsec-was-a-good-idea-turn-it-off/ Sun, 13 Sep 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/ipsec-was-a-good-idea-turn-it-off/ IPsec bound security to the IP address, then the industry took the address away. NAT, double NAT under CGNAT, NAT64 that will not carry it at all, no ports so no load balancing, the MTU tax, L2TP, PPTP and Windows interop — with diagrams, Cisco and Juniper documentation, a full diagnostic method, and the case for retiring it. 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.