Setup actual boot node, don't treat base node (first full node as boot node).
bootnode -genkey boot.key
bootnode -addr localhost:port -nodekey boot.key -verbosity 9
Start other nodes pointing the boot node
ex:
geth --datadir "data" --syncmode "full" --rpcport port --rpc --rpcaddr "localhost" --port port --rpccorsdomain "*" --rpcapi "personal,eth,net,db,web3,txpool,miner" --bootnodes "enode://************@localhost:port" --networkid 100 --ipcdisable --mine console