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[Bug] On Ubuntu, IPv6 works very badly. How to fix this?

There's an identified technical bug on VirtFusion-based systems, where cloud-init incorrectly deploys IPv6 on Netplan's routing configuration, upon installation of any Ubuntu operating system (18.04, 20.04, 22.04 or 24.04) and following a recent Netplan change on the treatment of the "gateway" parameter, which was deprecated on Ubuntu, but cloud-init doesn't provide an automatic adequate replacement on the "routes" parameter, as of 18-01-2026 or earlier.

This causes either very high packet loss (90%+) or entirely non-existent IPv6 connectivity, exclusively on Ubuntu-based systems.
Only IPv4 works adequately on the automatic provisioning. 

C-Servers has attempted some adjustments to the network provisioning in order to correct the fault, without any success.

There are three workarounds available, depending on your expertise level:
» disabling cloud-init and manually correct routing and the Netplan file (/etc/netplan/50-cloud-init.yaml) according to recent Ubuntu terms, ensuring "sudo netplan apply" is executed;
» installing Ubuntu Server directly from an ISO, with manual IPv4 and IPv6 configuration according to the specific network details provided at the "Network" section of the VirtPortal;
» installing Ubuntu Server from netboot.xyz with iPXE set on IPv6, and general install configurations first over IPv4, then over IPv6.

No other operating system, including Windows, is affected by this issue, and in most cases Ubuntu can be safely replaced by any Debian general version, or even Debian Unstable.

This issue will be escalated to VirtFusion. There's no ETA on a fix, at this moment. Though outside of our scope, we apologize for any inconvenience.