I'm using the Sonic client software to reach a TZ170 and it's set to use DHCP. The LAN DHCP server is also a DNS server. My VPN adapter gets a LAN IP, but I can't reach network resources by name -- only by IP. Is it possible for DNS to work through the VPN too?
The DNS server is listed in scope options. In fact, at the VPN client I just tried IPCONFIG/ALL and the VPN adapter has the DNS server address, so it appears that DHCP did assign it. Here's the IPCONFIG/ALL output for the VPN adapter:
Yes, it's possible. I've got some boxes out there running a similar setup. IMHO your problem is not DNS, but NETBIOS/WINS. Without appending your domain suffix automatically the Windows-host uses the NETBIOS-name, which is - by design - impossible over an IPsec-VPN. Sonicwall has an option to run NETBIOS over VPN, just forwarding the necessary broadcasts.
Perhaps you want to try manually adding the suffix? (DNS-tab in advanced TCP/IP-Settings). Afterwards everything should work like a charm :-)