IPv6 connectivity lost after starting tailscaled

SUPPORT QUESTIONS
1

Tailscale version - 1.12.3
Your operating system & version - Debian Bullseye

One (only one) of my machines is exhibiting strange behavior. After I start tailscaled, IPv6 connectivity on the machine is broken, except for traffic over the VPN.

Here is tailscale netcheck without the daemon running:

Report:
	* UDP: true
	* IPv4: yes, 54.73.152.114:48728
	* IPv6: yes, [2a05:d018:2f1:3d01::10]:58006
	* MappingVariesByDestIP: false
	* HairPinning: false
	* PortMapping: 
	* Nearest DERP: London
	* DERP latency:
		- lhr: 16.1ms  (London)
		- fra: 25.4ms  (Frankfurt)
		- nyc: 82.3ms  (New York City)
		- dfw: 118.1ms (Dallas)
		- sea: 136.1ms (Seattle)
		- blr: 147.3ms (Bangalore)
		- sfo: 154.2ms (San Francisco)
		- sao: 177ms   (São Paulo)
		- sin: 180.7ms (Singapore)
		- tok: 230.6ms (Tokyo)
		- syd:         (Sydney)

Here is tailscale netcheck with the daemon running:

Report:
	* UDP: true
	* IPv4: yes, 54.73.152.114:38041
	* IPv6: no
	* MappingVariesByDestIP: false
	* HairPinning: false
	* PortMapping: 
	* Nearest DERP: London
	* DERP latency:
		- lhr: 16.1ms  (London)
		- fra: 25ms    (Frankfurt)
		- nyc: 87.1ms  (New York City)
		- dfw: 122.6ms (Dallas)
		- sea: 138.4ms (Seattle)
		- blr: 148.8ms (Bangalore)
		- sfo: 153.8ms (San Francisco)
		- sao: 178.5ms (São Paulo)
		- sin: 182.8ms (Singapore)
		- tok: 231.6ms (Tokyo)
		- syd: 257.1ms (Sydney)

I setup this node using Ansible playbook which was used to setup a bunch of other machines, so it should have the identical configuration to all of them, and they are working fine.

What can I check to find out why this is happening?

2

I don’t know what happened, but this problem is no longer occurring.