I have a medium sized network with 2 domain controllers that handle DNS and DHCP. They are failovers for each other. I have the DNS entries on each server as 10.1.x.x and 10.1.x.y with a third DNS entry of an ISP DNS server. I have recently upgraded to Cisco managed switches SG300 series. For some reason my users are experiencing slow web page response when they try to access an internet site. It seems to be having trouble resolving the URLs via DNS. When users attach to my guest public network, which is before my firewall and switches, the responses are normal on the same Internet pipe. Should I be setting up DNS on the switches as well? Not real sure what the proper protocol is for this scenario.
Please let me know if anything is unclear or more info is needed.