I look after a bunch of remote offices that connect via VPN - a Cisco ASA 5505 in each office acts as Firewall and VPN end point.

Beyond that we keep things as simple as possible in the offices to minimise the support burden. We don't have any kind of server except in offices large enough to justify having someone dedicated to IT. Basically there is the ASA, some computers, a network printer and a switch.

One of the problems I am seeing in a lot of offices is that DNS requests looking up hosts inside our network often fail - I'm assuming timeouts due to the offices internet connection (they are all in developing world countries) having some sub-optimal qualities (e.g. high latency caused by VSAT segments, or packet loss.

The obvious solution to this is to have some sort of local DNS service that can serve local requests - so I think it would need to do zone transfers from our Microsoft Windows 2008 R2 DNS servers at HQ. However, simply installing Windows Servers in each office is both expensive, and creates a support burden. This got me thinking about pfsense/m0n0wall on embedded devices - those can act as a DNS server, and could be configured at HQ and sent out as just something that needs to be plugged into the network and can then be forgotten about by the staff locally. Maybe there are some alternatives to the ASA 5505 that include some DNS functionality.

Has anyone here dealt with the problem, either using some kind of embedded device, or found some other solution? Any gotchas or reasons to avoid what I have suggested?