DNS configuration with roaming wireless

Hi folks

I just don't have enough DNS-foo to sort this out.

Billion BiPAC 7402GL modem/router with 4 port switch
No problems connecting to my ISP
I have 3 devices connected to the Billion via ethernet
1 Time capsule
2 airport express

all 3 are set to Create a Wireless network with identical network name and security
all are in bridge mode
all get IP addresses via DHCP on the Billion and the Billion does NAT
DNS for all 3 is set to the IP of the Billion
DNS on the Billion is set to my ISP DNS (and I have the same problems if I set the DNS on the Billion to OpenDNS or Google's)

I have problems with some websites intermittently not loading - and for all the world it looks like a DNS problem - stale entries in a cache etc etc.

The computers connected via wifi to the network all have DHCP and their DNS set to the IP of the Billion.

Is this configuration correct?

I hope I have described the configuration clearly - three wireless access points all connected via ethernet to a model/switch.

with many thanks

Chris

I would use the "extend airport" option in the Time Capsule rather than setup a back fed WIFI network with in essence three separate WAPs.

Put the Billion as a bridge and use the Time Capsule for routing. Set the Time Capsule to provide DHCP with public DNS servers (provided your ISP will allow public DNS).