Start roscore slower without internet connection

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Hello everyone,

I tried to use ros multiple machines in a local area network. My viruelle machine connect to the router with ethernet and I found that roscore start much slower, when my router has no internet connection. And rosrun is also slower. There is no difference of its performance after roscore is established. But it is annoying, that I always have to wait a long time to start roscore.

So I'd like to ask, if ros checks networking, when it starts to run? Is there a solution to solve it.

Thank you!