Adding a subnet router to Tailscale App - SUDO in App-Shell?

Apps and Virtualization
1

I’m running Tailscale on my Truenas from the Apps-Catalog.
I’ve two routers (home and office) connected via Wireguard.
Truenas is running at home in a 192.168.15.xxx net and
in the office (192.168.1.xxx) I have a Grandstream UMC6302 PBX-System
connected to the router, that I want to reach over the tailnet
to use linphone on my andoid telefon.

Now I tried the following commands on the tailscale-shell:

echo 'net.ipv4.ip_forward = 1' | sudo tee -a /etc/sysctl.conf
echo 'net.ipv6.conf.all.forwarding = 1' | sudo tee -a /etc/sysctl.conf
sudo sysctl -p /etc/sysctl.conf

sysctl can’t write to the file. How do I get sudo in the tailscale-shell?
Is there a way to get the PBX into the tailnet?

(Configure a subnet router · Tailscale Docs)

2

Okay, got a solution now.
I found the “Accept DNS” option in the settings
and option to add “Advertise Routes”
I enabled “Accept DNS” and added under “Advertise Routes”
192.168.15.88/32 (the IP of the PBX-System)
Now I can use linphone outside of my WLAN.