diff --git a/eth/ethconfig/config.go b/eth/ethconfig/config.go
index b708e7a673..c01cd0f350 100644
--- a/eth/ethconfig/config.go
+++ b/eth/ethconfig/config.go
@@ -60,7 +60,7 @@ var LightClientGPO = gasprice.Config{
 // Defaults contains default settings for use on the Ethereum main net.
 var Defaults = Config{
 	SyncMode:           downloader.SnapSync,
-	NetworkId:          0,
+	NetworkId:          0, // enable auto configuration of networkID == chainID
 	TxLookupLimit:      2350000,
 	TransactionHistory: 2350000,
 	StateHistory:       params.FullImmutabilityThreshold,