On 08/10/2012 09:17 PM, Mark Trickett wrote:
Any comments about ICMP fragmentation setting would be appreciated, ie what to grep for and the like.
Well a good start is to try the tracepath program which will use PMTUD (Path MTU Discovery) to work out what is the largest packet that can can get to the destination. So here's an example going to my VM in the US, which gets throttled from an initial MTU of 1500 to 1492 at my ADSL router (hop 2): [chris@chris-laptop ~]$ tracepath csamuel.org 1: 192.168.1.112 0.449ms pmtu 1500 1: home.gateway.lan 16.306ms 1: home.gateway.lan 3.631ms 2: home.gateway.lan 3.560ms pmtu 1492 2: lns20.mel4.internode.on.net 47.293ms 3: te2-2.cor3.mel4.internode.on.net 46.315ms 4: gi7-1-0.bdr1.mel4.internode.on.net 220.653ms asymm 9 5: te5-0-0.bdr1.syd6.internode.on.net 220.674ms asymm 8 6: pos1-0-0.bdr1.lax1.internode.on.net 232.048ms 7: peering.la.us.iptransit.com 224.346ms 8: te2-2.r1.dal.us.iptransit.com 355.129ms 9: 204.26.63.166 284.330ms 10: ge-1-2.dal.rimuhosting.com 268.086ms 11: csamuel.org 257.300ms reached Resume: pmtu 1492 hops 11 back 54 If someone along the way is doing the wrong thing and blocking ICMP then I think you'll start to see 'no reply' after the bad hop. Best of luck! Chris -- Chris Samuel : http://www.csamuel.org/ : Melbourne, VIC