I have a private Ethereum P2P Network with a custom networkId and a custom genesis block. I would like to allow only invited peers.

If I have a custom networkId and a custom genesis block, will someone not having these two informations be able to connect to the network and sync with my private chain? Moreover, could someone query the node to obtain these informations?


1 Answer 1


The simple way to prevent connections to a private chain is to not publish the networkId and custom genesis block. If someone wanted to connect to your private chain, to do so they request those details from you, and their node can synchronize and obtain a copy of the chain.

Another way to prevent connections is to configure the network, use firewalls, etc. similar to an intranet.

  • There is no chance for a remote node to connect and sychronize if it's not knowing the networkid and genesis? Is it so that during the handshake, the remote node has to present some proof that he has the same genesis block, otherwise the handshake is terminated?
    – ivicaa
    Commented Nov 8, 2016 at 14:16
  • @ivicaa Yes, that sounds about right.
    – jeff
    Commented Jun 23, 2017 at 15:55

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