The recent update to systemd sent it to version 219. Per the changelog, .network files gained two new configuration values
Code:
IPForward
IPMasquerade
After the upgrade, my Gentoo box stopped routing packets to the internet. NAT was setup correctly, so the issue couldn't be there.
It appears that systemd by default sets the forwarding sysctl of each interface to 0. In order for packets to be forwarded, this must be set to 1. /etc/sysctl.conf was of no help.
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