Networking

Networking notes — routers, switches, DNS, TLS and the things that only break once a year.

Linux router

Linux router with WAN, LAN and DMZ

IP forwarding on and off, interfaces in systemd-networkd, and a default-deny iptables policy publishing a mail and a web server from the DMZ.

net.ipv4.ip_forward=1

DHCP and NTP for the LAN

Serve addresses from the router and push it as the LAN's NTP source.

EmitNTP=yes

Cisco

SYS-4-CONFIG_RESOLVE_FAILURE

What the log message means and how to stop it.

no ip domain-lookup

Certificates

Self-Signed CA

Run your own CA with mkcert and get every box on the LAN to trust it.

mkcert -install