how to know what DNS server is being used

[Steve Bertrand]

> On my registrars site I have two DNS servers listing. How 
> would I know that 1) both are working. 2) which one is being used.

1) http://dnsreport.com

2) # tcpdump -n -i <iface> | grep .53 | grep domain.com

(where domain.com == the domain I want to find out if the server is
answering for)

Generally, you can do this on all of your name servers, and get a good
idea of which ones are handling DNS resolution at any particular time.

Steve