GTM: If main site went down, will the LDNS resolve negative queries from its cache

any reply??

The answer is it depends on the configuration of the users LDNS... negative domain queries usually are cached (At least by Bind9 and it uses the domain SOA minimum value). But there's nothing your GTM can do about it, you would have to change this in the domain SOA itself...

 

 

I don't have my O'Reilley DNS&Bind book handy at the moment to copy the actual working (It's specified in an RFC though), but here's a link to the relevant pages in another book...

 

 

http://www.zytrax.com/books/dns/apa/ttl.html

 

 

H

Thanks for the reply Hamish,

 

So what will be the effect if the site went down, will the service be unavailable or DR site will serve even if the LDNS cache was configured for the default value "24 Hours"

LDNS will service from it's cache for as long as the TTL is set. You set the TTL yourself, so it's up to you.

 

 

However the whole idea of GTM is to NOT cache too much... You don't want LDNS to cache when GTM wants to resolve to a different address... The TTL should be set to the time you can handle clients tring to contact a down host (i.e. If SiteA goes down 2 seconds after you've given SiteA address to CustomerA, you set the TTL to the amount of time you can live with CustomerA not being able to work...

 

 

H