When squid setup as transparent proxy , returns ERR_CONNECT_FAIL on some sites . The server which squid runs on it is able to open those sites by lynx,wget,curl etc . Even if we manually set proxy in browser , those sites could open . Squid Cache: Version 3.1.20 Linux cache 3.5.0-22-generic #34-Ubuntu SMP Tue Jan 8 21:47:00 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux Here is tcpdump from one of clients when tries to open one of those sites GET / HTTP/1.0 Host: 80.75.1.4 Accept: text/html, text/plain, text/css, text/sgml, */*;q=0.01 Accept-Encoding: gzip, compress, bzip2 Accept-Language: en User-Agent: Lynx/2.8.8dev.2 libwww-FM/2.14 SSL-MM/1.4.1 HTTP/1.0 504 Gateway Time-out Server: squid Mime-Version: 1.0 Date: Wed, 27 Feb 2013 15:39:03 GMT Content-Type: text/html Content-Length: 376353 X-Squid-Error: ERR_CONNECT_FAIL 110 X-Cache: MISS from cache.mysquid.com X-Cache-Lookup: MISS from cache.mysquid.com:3128 Connection: close Also tried http://wiki.squid-cache.org/SquidFaq/SystemWeirdnesses#Can.27t_connect_to_some_sites_through_Squid >From this page http://wiki.squid-cache.org/SquidFaq/InterceptionProxy It causes path-MTU (PMTUD) to fail, possibly making some remote sites inaccessible. This is not usually a problem if your client machines are connected via Ethernet or DSL PPPoATM where the MTU of all links between the cache and client is 1500 or more. If your clients are connecting via DSL PPPoE then this is likely to be a problem as PPPoE links often have a reduced MTU (1472 is very common). But i have same problem with ethernet Here is tcpdump from one client: GET / HTTP/1.0 Host: 80.75.1.4 Accept: text/html, text/plain, text/css, text/sgml, */*;q=0.01 Accept-Encoding: gzip, compress, bzip2 Accept-Language: en User-Agent: Lynx/2.8.8dev.2 libwww-FM/2.14 SSL-MM/1.4.1 HTTP/1.0 504 Gateway Time-out Server: squid Mime-Version: 1.0 Date: Wed, 27 Feb 2013 15:39:03 GMT Content-Type: text/html Content-Length: 376353 X-Squid-Error: ERR_CONNECT_FAIL 110 X-Cache: MISS from cache.mysquid.com X-Cache-Lookup: MISS from cache.mysquid.com:3128 Connection: close ping -s 1500 80.75.1.4 PING 80.75.1.4 (80.75.1.4) 1500(1528) bytes of data. 1508 bytes from 80.75.1.4: icmp_req=1 ttl=58 time=5.28 ms 1508 bytes from 80.75.1.4: icmp_req=2 ttl=58 time=3.96 ms 1508 bytes from 80.75.1.4: icmp_req=3 ttl=58 time=4.28 ms ping -s 1473 80.75.1.4 -M do PING 80.75.1.4 (80.75.1.4) 1473(1501) bytes of data. >From 109.110.160.171 icmp_seq=1 Frag needed and DF set (mtu = 1500) >From 109.110.160.171 icmp_seq=1 Frag needed and DF set (mtu = 1500) --- 80.75.1.4 ping statistics --- 0 packets transmitted, 0 received, +2 errors ping -s 1472 80.75.1.4 -M do PING 80.75.1.4 (80.75.1.4) 1472(1500) bytes of data. 1480 bytes from 80.75.1.4: icmp_req=1 ttl=58 time=4.33 ms 1480 bytes from 80.75.1.4: icmp_req=2 ttl=58 time=4.32 ms --- 80.75.1.4 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 999ms rtt min/avg/max/mdev = 4.320/4.329/4.338/0.009 ms traceroute --mtu 80.75.1.4 traceroute to 80.75.1.4 (80.75.1.4), 30 hops max, 65000 byte packets 1 x.x.x.10 (x.x.x.10) 0.820 ms F=1500 0.681 ms 0.243 ms 2 y.y.y.1 (y.y.y.1) 2.969 ms 3.185 ms 2.994 ms 3 217.218.181.193 (217.218.181.193) 2.836 ms 2.381 ms 2.487 ms 4 217.218.185.22 (217.218.185.22) 3.617 ms 2.957 ms 3.176 ms 5 78.38.119.237 (78.38.119.237) 2.050 ms 1.808 ms 2.264 ms 6 217.11.30.250 (217.11.30.250) 3.522 ms 3.962 ms 2.674 ms 7 * 80.75.1.4 (80.75.1.4) 3.507 ms * tracepath 80.75.1.4 1: cache.mysquid.com 0.092ms pmtu 1500 1: x.x.x.10 0.380ms 1: x.x.x.10 0.309ms 2: y.y.y.1 3.390ms asymm 7 3: 217.218.181.193 2.671ms asymm 5 4: 217.218.185.22 2.944ms asymm 5 5: 78.38.119.237 1.684ms 6: 217.11.30.250 4.020ms 7: 80.75.1.4 3.915ms reached Resume: pmtu 1500 hops 7 back 58 -- View this message in context: http://squid-web-proxy-cache.1019090.n4.nabble.com/Squid-transparent-proxy-connection-fails-on-specific-sites-tp4658746p4658809.html Sent from the Squid - Users mailing list archive at Nabble.com.
