Is there no way to have the Draytek 2860 point to OpenDNS for DNS resolution, but have the DHCP clients point to the Draytek?

Seems I can only specify DNS settings for DHCP and set Draytek to use those settings to override ISP.

You can, just set up an extra VLAN with the DNS settings you want to use for the router and set the router to use that subnet's DNS settings.
Then the LAN clients can use the DNS settings configured in the DHCP settings of the original LAN subnet.

What a faff! Usually on a router you can specify WAN DNS settings separately from the DHCP DNS settings.

It's not a big issue I guess. Just a nice to have.

I've submitted it as a feature request, but I have no idea how responsive Draytek are to those!

I'd like to do this on my 2925n, to resolve local dns queries with the draytek.

I've set up a vlan which has lan3 as the subnet. I've put the opendns servers in the details page for lan3, and selected "Force router to use DNS IP address settings specified in Lan3"

Should I leave the dns settings in lan1 details page blank, so the local dns cache is used? Or enter the 2925 address there?

I've migrated from a dd-wrt environment, and finding it very frustrating that I can't just use hostname to resolve services on my network local network.

The whole thing seems to be a bit of a mine field. I think that there's a fundamental kludge in the way dns addresses are stored internally but because it works (well?) 99.9% of the time nobody has ever sat down and looked at it. Does not affect me because I normally use a server which handles DNS/DHCP/RADVD etc. and there is nothing wrong with my ISPs DNSs.

But, yes the settings are a bit lacking and spagettified.

You can (on 2860) use Applications >> LAN DNS / DNS Forwarding to redirect all (*) DNS queries but I have only tested briefly and it may have it's own issues.

Not sure if I've missed something here, but it is possible to configure WAN and LAN DNS differently.
Surely setting the DNS server in the LAN DHCP setup determines what the (DHCP) clients use, and the DNS server on the WAN can be set in the appropriate WAN setup page ?
This is exactly what I'm doing on a 2925 'though admittedly only on a Virgin cable connection, no the BT PPPoE one.
Cheers
Simon