lanning wrote: > On Mon, 18 May 2009 15:04:59 +0200, Aleksandar Ivanisevic > <[email protected]> wrote: >> I had to lower down mtu to 1300 to make google work again. IPs not >> working all seem to be in or around the 74.125.39.0/24 netblock. > > This seems like a Path MTU Discovery issue. (not specifically Google) > > MTU is not known past your physical interface.
Packets of weird sizes then, call them what you want :) > Try turning off Path MTU Discovery and putting your MTU back at 1488. > (This is not really a solution, but a test.) > You can try pinging with larger and larger packet sizes to see what > router is dropping on the larger packet size, without returning an > ICMP. This is what I always do first. The magic limit seems to lie exactly at 1300 bytes. [r...@proxy ~]# ping 74.125.39.100 -s 1272 PING 74.125.39.100 (74.125.39.100) 1272(1300) bytes of data. 1280 bytes from 74.125.39.100: icmp_seq=1 ttl=245 time=39.4 ms 1280 bytes from 74.125.39.100: icmp_seq=2 ttl=245 time=37.9 ms 1280 bytes from 74.125.39.100: icmp_seq=3 ttl=245 time=42.6 ms --- 74.125.39.100 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2001ms rtt min/avg/max/mdev = 37.986/40.051/42.686/1.960 ms with pmtu discovery [r...@proxy ~]# ping 74.125.39.100 -s 1273 PING 74.125.39.100 (74.125.39.100) 1273(1301) bytes of data. --- 74.125.39.100 ping statistics --- 9 packets transmitted, 0 received, 100% packet loss, time 8009ms anything over 1300 without pmtu disc gets truncated replies, so there is definitely something fishy there [r...@proxy ~]# ping 74.125.39.100 -s 1273 PING 74.125.39.100 (74.125.39.100) 1273(1301) bytes of data. 1280 bytes from 74.125.39.100: icmp_seq=1 ttl=245 (truncated) 1280 bytes from 74.125.39.100: icmp_seq=2 ttl=245 (truncated) 1280 bytes from 74.125.39.100: icmp_seq=3 ttl=245 (truncated) _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
