Hello everyone, I am experiencing very strange problem never had before. A Small local network with eth1 as WAN static connected to DSL Router and eth0 as LAN 192.168.100.254 Squid3 with CentOS6 on 8080 port transparent and simple masquerading and routing iptables. I had configured mac address with ip binding but it is not very efficient have removed it now. Used Named caching dns but now using pdnsd as dns server and no dhcp static ip assign to clients. The problem is the users experience limited connectivity on their end (Windows OS) with yellow caution icon on the network connection icon. We can ping the server i.e. 192.168.100.254 but can not do any dns lookups or browsing then it start working normal automatically after 10-15mins. Sometimes it does not even work for hours. The most strange thing is the other clients they are using the internet. P.S I tried changed NIC's , Switch , Cables and multiple END-Hosts. Could someone please advice what is the problem. Thanks.