Configure DNS for SSL Vpn under config vpn ssl settings.
config vpn ssl settings
set dns-suffix "Domain_Name"
set dns-server1 192.168.1.1
set dns-server2 192.168.1.2
You should also configure dns-suffix, otherwise vpn clients will only be able to ping IP addresses or fully qualified host names.
So i you have a server named intranet.domain.com on IP 192.168.1.100 vpn users can ping 192.168.1.100 and intranet.domain.com but not hostname intranet unless you set the dns-suffix to "domain.com"