So all of the DNS information in configured on the concentrator side - no
client side configuration necessary.
The VPN server pushes a set of DNS servers and your /etc/resolv.conf gets
replaced with one pointing at those servers. When the connection shuts
down, your saved file gets restored.
There's some additional interception going on though, as I find even if I
block the overwriting of resolv.conf that some packets targeted to the
Internet still get lost.