> Thanks a lot for your response . > I used sniffer tool to catch the packet in both Poly graph Server > (10.56.233.99) and Squid server side (198.18.24.3). > > I could see 198.18.24.3 send out SYNs, they SYNs were also could be > captured in PolyServer(10.56.233.99) side , but no ack were genenated > by the 10.56.233.99 server . Ok, if you cant see the SYN/ACK from 10.56.233.99, it could be; - if the box is multi-homed the SYN/ACK may be being routed out a different interface - the traffic may be being dropped by iptables (which sits between tcpdump and the OS) Double check (or maybe post) your iptables configuration. Also send the output of netstat -ant | grep 198.18.24.3
