[plug] Need help deciphering tcpdump

[Craig Ringer]

> Can anyone here explain what the following lines of tcpdump output mean?
> In particular I'm unsure why the port number has a z in front of it
> ("z3950"); but mainly want to know what the icmp message below it means
> and how to fix it.
> 
> 15:54:27.906400 134.243.85.3.z3950 > 130.95.39.9.1040: . 773:2153(1380) ack 597 win 64860 (DF)
> 15:54:27.906573 130.95.39.9 > 134.243.85.3: icmp: 130.95.39.9 unreachable - need to frag (mtu 1400) [tos 0xc0]

I'm no expert on this, but I'd say you've got a network segment 
somewhere between you and and the host you're talking to that has a 
lower MTU than your host is configured for. As a test, try lowering your 
MTU and seeing what happens.

That's probably the explanation for the ICMP 'need to fragment' message, 
anyway. I don't know about the port number 'z' prefix at all, sorry.

Craig Ringer


_______________________________________________
plug mailing list
plug at plug.linux.org.au
http://mail.plug.linux.org.au/cgi-bin/mailman/listinfo/plug