[opensuse] ICMP Path MTU message
I just read a blog about packet fragmentation: https://blog.cloudflare.com/ip-fragmentation-is-broken/ And then I ran the test they link to at: http://icmpcheck.popcount.org/ The first test timed out, saying: "The request timed out. Looks like the ICMP Path MTU message was not delivered to you." The second test passed, saying: "All good! IP fragments were successfully delivered to your host." To investigate the failure of the first test, I started tcpdump and reran the test. The test gave the same result (good, I suppose) and tcpdump said: acer-suse:~ # tcpdump -ni any icmp or icmp6 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes 17:14:00.320873 IP 139.162.188.91 > 192.168.1.72: ICMP 139.162.188.91 unreachable - need to frag (mtu 905), length 136 17:14:00.332740 IP 139.162.188.91 > 192.168.1.72: ICMP 139.162.188.91 unreachable - need to frag (mtu 905), length 136 17:14:00.344596 IP 139.162.188.91 > 192.168.1.72: ICMP 139.162.188.91 unreachable - need to frag (mtu 905), length 136 ^C 3 packets captured 3 packets received by filter 0 packets dropped by kernel I'm no tcpdump expert but it looks to me that it is saying that it did receive three ICMP Path MTU messages. Is that correct and is anybody able to explain what's going on? (hopefully will save me hours of RT-wrong-FM :) TIA, Dave PS I spent all this morning investigating why I'd lost network connection until I discovered an intermediate network switch that my wife had accidently turned off :( Perhaps I should have bought managed switches! -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
On 10/13/2017 12:35 PM, Dave Howorth wrote:
PS I spent all this morning investigating why I'd lost network connection until I discovered an intermediate network switch that my wife had accidently turned off :( Perhaps I should have bought managed switches!
What you need is a managed wife! ;-) -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org
On Fri, 13 Oct 2017 17:35:42 +0100
Dave Howorth
PS I spent all this morning investigating why I'd lost network connection until I discovered an intermediate network switch that my wife had accidently turned off :( Perhaps I should have bought managed switches!
Where else is she going to plug the vacuum cleaner? -- Bob Williams System: Linux 4.4.87-25-default Distro: openSUSE 42.3 (x86_64) Desktop: KDE Frameworks: 5.32.0, Qt: 5.6.2 and Plasma: 5.8.7
participants (3)
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Bob Williams
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Dave Howorth
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James Knott