Synchronized random values at multiple GameObjects

Hi,
I have multiple ammunition spawn points.
Each of these should spawn the same (random) weapon on every client, and after some random time spawn again a random weapon.

Everything is working except that the Random is not really Random.
I get the same Random values again after restarting the game.
Is there a possibility to use a different seed for each new start of the game? (Which is synchronised over the network too, so that all clients have the same values)

Thanks in advance,
John