well, Amazon has no Support-Technicans or no Technicans in their Support-section
In sum the Support-replay was "It's a Networkproblem, the kindle works"
It looks like the kindle is only able to handle c-class networks.
The netmask is the only difference in the network-settings.
And in a Homenetwork (192.168.0.x /24) the kindle works properly.
But I found no information about that in the Datasheet and the support
also can't say anything to this question (typical reply: "it supports b/g/n")
what have I learned:
if google did no have an answer, neither the support