product RUT955T03XXX, firmware RUT9_R_00.07.04.2
When you go to diagnostics and select "Ping", "IPv4" and give a DNS name as address, the router resolves it to IPv6 instead.
I believe this is a bug. I would expect the router resolves the DNS name to its IPv4 adress and attempts a ping on that.
Here is a screenshot. As you can see from the shell:
"nei-rai2.vpn" does have a valid IPv4 adress and also answers to it.
However, there is no valid IPv6 routing to this adress. Therefore, the router responds "permission denied".