What does RUNNING in ifconfig output mean?
The running state is typically associated with the UP state of the interface, i.e. is the interface turned on, and is there a link over that interface (ip address, etc)
A good way to word it:
RUNNING
Indicates that the required resources for an interface
are allocated. For some interfaces this also indicates
that the link is up.
One way to change the running state is to stop it, i.e. down the interface.
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It means there is a network link to a switch, ie its plugged in.