SSL VPN wrong tunnel address

We have a user group and an IP-range, these two are connected via a portal, so far so good. The IP-range is 1.1.1.21 - 1.1.1.40, but when a user from the user group signs in he gets the tunnel address 1.1.2.159, the next sign in gets the correct one: 1.1.1.21. The IP-adress 1.1.2.159 is not used in the firewall.

I hope someone can help!