Cannot make DHCP reservation out of the DHCP pool

Hello,

I foud a bug in the router:

I am using network 172.16.20.0 with subnet 255.255.252.0 wich means i can use IP adresses from 172.16.20.1 until 172.16.23.254.

When i setup my DHCP server on the router (from 172.16.20.1 to 172.16.20.100) i cannot make a DHCP reservation outside of this DHCP pool.

Is there a workaround or am i doing something wrong?

Thanks in advance.