Bitcoin Core peer over LAN problem


I am having trouble getting my Start9 Bitcoin Core to use another node on my LAN as it’s peer. It seems to be connecting, but something is not right and it is working only intermittently

I have a Windows/Bitcoin Core fully sync’d and I want to use this as the peer (seeder) to do an IBD on the second computer, which is running Start9 with Bitcoin Core.

Here is how I set up the computers in a peer relationship. On the Start9 computer (where I am trying to IBD) I input the IP+port of the peer (seeder) computer as follows: Bitcoin Core->Config->Peers->Add Nodes->Hostname (IP) with Port. Using the IP+Port (8333) from the first computer on the LAN. It does connect as I can see the Start9 computer says 1 connection, and the Windows (seeder) computer also lists the IP of the Start9 computer. I also turned off on “Disable Peer Discovery” so that the Start9 computer only connects to the seeder computer over LAN, does not connect to external peers.

Some odd issues I am noticing:

1 -The Block Height gets stuck at very low numbers, and then the syncing is intermittent because it reaches the block height then has to stop (~150, ~350K, ~650K, etc). It is slow due to this. When I do IBD over external peers, the Block Height goes straight to where it should be ~850K.

2 - On the seeder computer I can see the sent & received data and it is very low, 23kb and 1 kb respectively. Ping is 2ms so confirms it is connecting and a quick connection (external peers are ~100ms). I would expect this to be more like 500Gb data transfer, the block database (am I wrong?)

3 - On the Windows computer it lists the Start9 IP as “Unroutable” (under Network) , whereas all the external peers say “IPv4”

It’s just not working the way it should, and I’m sure I’ve set something up incorrectly.

Any ideas on how to fix this or what I can try?

Thank you,


At first glance, it would seem to me to be something to do with this Windows machine or your networking setup. If even Windows is reporting that it’s can’t see the Start9 server properly you could look to turning off your firewall on Windows and anything that might be causing issues on your router.

With regards to networking, if you have a weird NAT setup, like a router plugged into another router, that might be a cause, as too might something like the two machines being on different subnets.

Also, if you’re looking to just get the blockchain quickly, you might prefer just to take a few moments to follow this guide instead… Start9 | Blockchain Migration

Hi Stu,

Thanks for the reply. I do have a dual routers so was hopeful it was that. The two computers were plugged into different routers so I rearranged them and tried again. Still have the same issue. I don’t understand because the Start9 computer is clearly somewhat working - it is only connected to the Windows machine as a peer, yet the Windows computer still says almost no data transfer to this Start9 computer.

I’m not super well versed with network settings on the router. Is there anything I should look for?

I did not approve the Root CA certificate authority on the Windows computer, I wonder if it has to do with this. I can also try temporarily disabling the Windows Defender firewall to see if that makes a difference.

The main reason I’m doing this is to test the computer hardware for IBD, and removing my (slow) external internet speed is worthwhile. Not looking to get the blockchain quickly like copying it over. Thank you for sending that.

Somewhere between 99% and 100% of the time when you plug a server into a standard router, then a client computer into the same router, you’ll have 0 problems.

In your case, since you did have a complex NAT setup that could prevent some parts of the network from accessing other parts of the network, it would make sense to look at what else you might have done that would be difficult for me to guess at.

I’d check the IP addresses of the server and the client machine to make sure they are on the same subnet.

Yes, you’ll also have to look at your Windows setup. While it sounds like a networking issue, if Windows is blocking something via the firewall, a static IP, a VPN turned on… and all manner of similar things, that would also explain it.

The Root CA would not affect networking.