I have setup a number of DNS User experience models via APM (using the latest and greatest, whatever that is) The polling is taking place every 5 minutes and the results make sense in that every other poll (the lookup is for a name outside of our domain) is significantly less than the previous poll, so over 20 minutes the responses are 40ms, 2ms, 43ms, 1ms.....etc. Again this makes sense to me in that I ASSUME that this is due to caching. My first question is, assuming I want to keep the polling frequency and don't want to have the folks in charge of DNS change anything on their , if I want to get rid of the cached responses is there something I can do on the APM side to specify that I don't want cached results i.e. some cool little software switch that I can append to the name I'm looking up that would force the DNS server to go out and do a recursive lookup???? And second is it more telling to keep it like it is ??? in that it actually shows me that my DNS servers have the capability of caching entries and if at some point I just started seeing 40 plus millisecond responses that this would be an indication that something is amiss ? How are some of you handling/accounting for caching issues, this would also seem to extend to HTTP as well as DNS... Thanks in advance.
