Setting up private network or local cluster

This page describes how to set up a local cluster of nodes, advise how to make it private, and how to hook up your nodes on the eth-netstat network monitoring app. A fully controlled ethereum network is useful as a backend for network integration testing (core developers working on issues related to networking/blockchain synching/message propagation, etc or DAPP developers testing multi-block and multi-user scenarios).

We assume you are able to build geth following the build instructions

Setting up multiple nodes

In order to run multiple ethereum nodes locally, you have to make sure:

each instance has a separate data directory
each instance runs on a different port (both eth and rpc)
the instances know about each other
[ONLY TEMPORARY]: only one instance does mining ( until #555 fixes dag versioning in ethash, /tmp/dag cannot be shared by multiple instances.)

You start the first node (let's make port explicit)

geth --datadir="/tmp/eth/60/01" -loglevel 5 -logfile /tmp/eth/60/01.log -port 30301 -rpc -rpcport 8101  console

We started the node with the console, so that we can grab the enode for instance:

> admin.nodeInfo()
enode://8c544b4a07da02a9ee024def6f3ba24b2747272b64e16ec5dd6b17b55992f8980b77938155169d9d33807e501729ecb42f5c0a61018898c32799ced152e9f0d7@9[::]:30301

[::] will be parsed as localhost (127.0.0.1). If your nodes are on a local network check each individual host machine and find your ip with ifconfig (on Linux and MacOS):

$ ifconfig|grep netmask|awk '{print $2}'
127.0.0.1
192.168.1.97

Now you can launch a second node with:

geth --datadir="/tmp/eth/60/02" -loglevel 5 -logfile /tmp/eth/60/02.log -port 30302 -rpc -rpcport 8102 -bootnodes="enode://8c544b4a07da02a9ee024def6f3ba24b2747272b64e16ec5dd6b17b55992f8980b77938155169d9d33807e501729ecb42f5c0a61018898c32799ced152e9f0d7@127.0.0.1:30301"

You can test the connection by typing in geth console:

> net
{
  listening: true,
  peerCount: 1
}
> admin.peers
...

Local cluster

As an extention of the above, you can spawn a local cluster of nodes easily. It can also be scripted including account creation which is needed for mining. See gethcluster.sh script, and the README there for usage and examples.

Private network

An ethereum network is a private network if the nodes are not connected to the main network nodes. So in this context private only means reserved or isolated, rather than protected or secure. Since connections are valid only if peers have identical protocol version an network id, you can effectively isolate your network by setting either of these to a non-canonical value. We recommend using the semantic networkid command line option for this. Its argument is an integer, the canonical network has id 0 (the default).