hello Experts I was trying to upgrade our router from a Cisco 800 series to a sonicwall. well it turns out the sonic walls wifi is defective and it needs to be returned. I put the Cisco 800 series back in place but now nobody can connect to the internet and when I try to troubleshoot it tells me that the DNS server isn't responding. I'm at a business and the Internet has not been working for 6 hours and I really really need help with this. DNS is running off of our main domain controller and so is exchange and so is DHCP. our domain controller has Small Business Server 2012 on it. Please help!!