- How is it different than networkID?
It is not. chainID is a different name but refers to the same thing.
- Is chainID and networkID needed in every block or just the genesis
block?
This is only in the genesis file, not in blocks. Here is the description of the very first block of the mainnet (yeah, I'm currently syncing in fast mode :D )
> eth.getBlock(0)
{
difficulty: 17179869184,
extraData: "0x11bbe8db4e347b4e8c937c1c8370e4b5ed33adb3db69cbdb7a38e1e50b1b82fa",
gasLimit: 5000,
gasUsed: 0,
hash: "0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3",
logsBloom: "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
miner: "0x0000000000000000000000000000000000000000",
mixHash: "0x0000000000000000000000000000000000000000000000000000000000000000",
nonce: "0x0000000000000042",
number: 0,
parentHash: "0x0000000000000000000000000000000000000000000000000000000000000000",
receiptsRoot: "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
sha3Uncles: "0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347",
size: 540,
stateRoot: "0xd7f8974fb5ac78d9ac099b9ad5018bedc2ce0a72dad1827a1709da30580f0544",
timestamp: 0,
totalDifficulty: 17179869184,
transactions: [],
transactionsRoot: "0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421",
uncles: []
}
> web3.eth.chainId()
"0x5b7d"
- Can you give a specific example of what it means when it says chainID
is used "for replay protection"?
You may find your answer here