On Thu, 2009-04-09 at 00:39 +0300, Mohammad Khalil wrote: > is there any tool that can monitor the DNS behavior ?? > for example , the resolving process and if there are any errors ?? If you want to monitor this from a Cisco device, IP SLA Monitor "type dns" is the thing to search for. It can do DNS lookups and tell you how long it took. Regards, Peter