DNS - when my internet is connected but not working

[greggpb]

Hi guys,
I am having an intermitante issue, they are the best kind, when our office will loss the ability to resolve dns for 30min to an hour at the time.. it has been happening for the last 3 months.

Where woudl you start looking to find the issue and in an ideal world how would you setup up the dns servers ?

 

[syntax]

What are u using internally as a dns server? What is your upstream dns ?

 

[RSkeens]

I would start by using OpenDNS or Google Public DNS exclusively, if this is already not configured.

 

[bekdik]

Check with you isp for the correct dns's to use

 

[greggpb]

At the Moment we have a

*sbs server running DNS( I believe this is necessary for internal resolution?)
*a Firewall(pfsense box)
*a Adsl modem(I think it is being dial as a interface on the pfsense box).

What would the ideal setup be.. as we have had a company setting it up and we have had numerous problems ?

They are blaming the Adsl Modem ?