Explanation on TCP-checksum errors

[Carol Giardello]

Hi,

we're running a windows-based tcpip newtwork.

Once in a while a single server stops working, it freezes, does not
respond to mouse or keyboard.

To get some idea whats going on with the network I sniffed using the
latest ethereal (0.10.12).

I was stunned as ER states that every outgoing tcp-packet from that
server has a wrong TCP-Checksum!

Here my question(s):
- might ER be mistaken? For comparison reasons I sniffed a different
network. Here everything seems to be ok, so I suppose ER ain't wrong.

- if the tcp-checksum is really bad, why are those packets not
rejected/dropped? Communication seems to take place, does tcp not
check for good/bad checksum?

- waht's the reason for that?

 

[Guest]

Bad nic. Had a problem something like this years ago. Replaced the nic with a
brand name nic and problem disappeared. You could also have a flaky port on a
switch. Check the cables and if you can, move port on switch then swap nic. I
doubt that it's a driver...