First the facts:
I tried to use nodegroups as described here.
nodegroups:
web: 'salt-master1,salt-master2'
If I run ...
salt -N web test.ping
... it results in:
No minions matched the target. No command was sent, no jid was assigned.
ERROR: No return received
Changed my nodegroup to:
nodegroups:
web: 'salt-master1'
Voila ...
salt-minion1:
True
I also tried the other notations to define a nodegroup as described in the linked documentation.
How i get it work with more than one host?
I recognized my fault.
Did not realize the L@ notation is explicit for a list of hosts.
Solution for interesting people:
nodegroups:
web: 'L@salt-master1,salt-master2'
results in:
salt-minion1:
True
salt-minion2:
True