Geth Connections – How to Allow Connections from Specified Nodes in Geth

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I'm setting up a private network with 10 geth nodes for my organization's own use, however I don't want outside nodes to accidentally (or intentionally) connect to our geth nodes. The nodes are hosted on public servers so we can access them anywhere, is there some way so the geth nodes in our private net will only allow peer connections from each other and block connections from other nodes. Currently we use the static-nodes.json to make the 10 geth nodes to connect to each other, disabled discovery, however I'm not sure if that's enough to block unwanted outside nodes connection attempts? Thanks.

Best Answer

I'm not sure how deep into geth you want to go, but p2p/Server contains a property called "NetRestrict" that allows you to restrict connections to particular IP networks.

cmd/bootnode/main.go is a working example that accepts the "netrestrict" flag. It looks like Geth hasn't quite implemented this yet, but it should be fairly easy to implement yourself.

Data format

[
      "enode://f4642fa65af50cfdea8fa7414a5def7bb7991478b768e296f5e4a54e8b995de102e0ceae2e826f293c481b5325f89be6d207b003382e18a8ecba66fbaf6416c0@33.4.2.1:30303",
      "enode://pubkey@ip:port"
]

You can configure permanent static nodes by putting something like the following into <datadir>/static-nodes.json

Common problems with connectivity

Sometimes you just can't get connected. The most common reasons are:

Your local time might be incorrect. An accurate clock is required to participate in the Ethereum network. Check your OS for how to resync your clock (example sudo ntpdate -s time.nist.gov) because even 12 seconds too fast can lead to 0 peers.
Some firewall configurations can prevent UDP traffic from flowing. You can use the static nodes feature or admin.addPeer() on the console to configure connections by hand.

Sources:
1. https://github.com/ethereum/homestead-guide/blob/master/source/network/connecting-to-the-network.rst#static-nodes-trusted-nodes-and-boot-nodes

[Ethereum] Automatic peer discovery in a private blockchain

No, there is no peer discovery methods other than modifying the boot nodes.

The IP addresses are configured in the source code of the clients. If the IP changes, the list of the last bootstrap node that it connected to will change (the old IP will be removed and when the node connects again the new IP will be stored in the list).

What are the peer discovery mechanisms involved in Ethereum? explains a lot.

Best Answer

Related Solutions

[Ethereum] How to use static-nodes.json / trusted-nodes.json to prevent connection loss on private network

Data format

[Ethereum] Automatic peer discovery in a private blockchain

No, there is no peer discovery methods other than modifying the boot nodes.

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