I claim (the term 'claim' in my lingo means: take what I say with
increased skepticism) that Wireshark figures out which decoder to
apply by looking at udp/tcp port numbers and consulting an internal
look-up table. I'm unclear how to examine that look-up table, but I
suspect we can peek at inputs to it via items like Edit, Preferences,
Protocols, HTTP, TCP Ports:
80,3128,3132,5985,8080,8088,11371,1900,2869,2710 [Although I see
nothing similar for ... Protocols, ISAKMP]
And thus that Wireshark will not apply its ISAKMP decoder to an ISAKMP
frame slotted into a port other than 500.
Which is where the Analyze, Decode As... feature comes into play.
Give that a try, see how Wireshark then portrays your port 8500
traffic.
Looks like one can even save such choices:
"Once you added one or more "Decode As..." definitions, go to "Analyze
-> User Defined Decodes..." and choose "Save". This will save these
"Decode As..." definitions in your current configuration profile. So
you can even have a different set of custom port mappings for
different setups by defining multiple configuration profiles."
http://ask.wireshark.org/questions/14213/protocol-port-change-or-port-adding-in-wireshark
I have not done this myself, but it sounds coherent.
hth,
--sk
On Thu, May 8, 2014 at 4:16 PM, Perry Smith <pedzsan@xxxxxxxxx> wrote:
> Hi,
>
> AIX sends its isakmp packet on port 8500 instead of 500. Well... it sorta does both.
>
> In any case, if the packet is on port 500, wireshark marks the protocol as isakmp and decodes the payload. If the packet is on port 8500, then the ethernet, IP, and UDP parts are decoded but not the isakmp part. Is that because of the port number or is it because the packet is not really properly formatted? I can't find a user config option that is set to 500.
>
> I found this:
>
>> # Set the port for IPSEC/ISAKMP messagesIf other than the default of 10000)
>> # A decimal number
>> # tcpencap.tcp.port: 10000
>
> but when I set that to 8500, it doesn't make a difference that I can see.
>
> I'm fighting two unknowns. Are my isakmp packets bad and that is why wireshark is not formatting them or is it because they are on port 8500 instead of 500?
>
> Thank you,
> Perry Smith
>
>
>
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