It will be helpful to use NAS-IP-Address = <source ip address> instead of 127.0.1.1 by default.
link to the forum topic https://forum.vyos.io/t/radius-not-setting-nas-ip-as-source-ip/4661
It is possible if replace string in /etc/hosts e.g.
#127.0.1.1 vyos 198.51.100.1 vyos
The better solution, change source code libpam-radius-auth