Maybe an oddly specific setup, but in case anyone else is affected... Run a trixie instance on Ec2 with multiple NICs. Setup one to have a static ip with netplan or networkd. Reboot, and cloud-init will run dhcpcd after networkd. This breaks the address one hour later.
cloud-init is trying to discover the gateway for each NIC's policy routes. But since it does this in cloud-init-network, networkd has already been started. When dhcpcd gets a lease, it adds it to the interface with a finite lifetime. Once that expires, the kernel removes the IP. networkd needs you to bounce the interface to recover. I don't know if dhcpcd has changed behavior, or if cloud-init is driving it incorrectly. udhcpc doesn't seem affected. Ross PS - will be out of town again for our meeting this month. Hope to catch up with folks in September.
