Hello Michael,
>>> "STEINECKE Michael SD-G (AREVA NP GmbH)"
<Michael.Steinecke@xxxxxxxxx> 08/28/06 4:33 AM >>>
> Hello folks,
>
> i've a bit strange issue in the communication between a Server and
his
> client (a microcontroler).
> The controler send "Echo Reply" packets without a corresponding
ICMP
> requests. Is there another way how this can happen then an program
or
> firmware error? Something like an TCP packet that requests a ICMP
Echo
> par example?
>
> Best Regards
> Michael Steinecke
Does you controller have multiple NIC interfaces? If so, then
depending on how you've set up your route statements on
the controller (assuming that you can) it's possible that replies
received on one NIC interface will be returned out a different
NIC interface. IP addresses more than one hop away could
be taking a "default" route (out the NIC interface towards
your server).
Take a look at the destination IP address (where the ping reply
is supposed to go to) and the destination MAC address for the
ping reply. This should give you a clue on who/what might be
generating the original request.
Then again if it's some type of specialized controller, then I
wouldn't be surprised to see the vendor doing something
non-conventual like using ICMP echo replies to send signalling
information to some other station(s).
I've also seen some devices that use an an undocumented
private NIC setup internally. I've had a few occasions where
these back-end packets have leaked out the one public NIC.
I hope this find this useful.
Jim Young
