Network Configuration

If you want to support the Bitcoin network, you must allow inbound connections.

When Bitcoin Core starts, it establishes 10 outbound connections to other full nodes so it can download the latest blocks and transactions. If you just want to use your full node as a wallet, you don’t need more than these 10 connections—but if you want to support lightweight clients and other full nodes on the network, you must allow inbound connections.

Servers connected directly to the Internet usually don’t require any special configuration. You can use the testing instructions below to confirm your server-based node accepts inbound connections.

Home connections are usually filtered by a router or modem. Bitcoin Core will request your router automatically configure itself to allow inbound connections to Bitcoin’s port, port 8333. Unfortunately many routers don’t allow automatic configuration, so you must manually configure your router. You may also need to configure your firewall to allow inbound connections to port 8333. Please see the following subsections for details.

Testing Connections

The BitNodes project provides an online tool to let you test whether your node accepts inbound connections. Before using BitNodes, you must first ensure that your node is fully synced with the block chain. Once you’ve done so, start Bitcoin Core (either the GUI or the daemon), wait 10 minutes, and then visit the Bitnodes page. The tool will attempt to guess your IP address—if the address is wrong (or blank), you will need to enter your address manually.

Bitnodes Tool

After you press Check Node, the tool will inform you whether your port is open (green box) or not open (red box). If you get the green box, you don’t need to do anything—you accept inbound connections. If you get the red box, please read the enabling connections subsection.

For confirmation that you accept inbound connections, you can use Bitcoin Core. Bitcoin Core can’t tell you directly whether you allow inbound connections, but it can tell you whether or not you currently have any inbound connections. If your node has been online for at least 30 minutes, it should normally have inbound connections. If want to check your peer info using Bitcoin Core, choose the appropriate instructions below:

• Peer info in Bitcoin Core GUI

• Peer info in Bitcoin Core daemon

GUI Peer Info

In the bottom right corner of the Bitcoin Core GUI are several icons. If you hover over the signal strength icon, it will tell you how many connections you have. The icon won’t turn green until you have more than 10 active connections, which only happens if inbound connections are allowed.

Active connections

For confirmation, you can go to the Help menu, choose Debug Window, and open the Information tab. In the Network section, it will tell you exactly how many inbound connections you have. If the number is greater than zero, then inbound connections are allowed.

Debug window with inbound connections

If you don’t have inbound connections, please read the instructions for enabling inbound connections.

Daemon Peer Info

The getconnectioncount command will tell you how many connections you have. If you have more than 10 connections, inbound connections are allowed. For example:

$ bitcoin-cli getconnectioncount
52

For confirmation, you can use the getpeerinfo command to get information about all of your peers. Each peer’s details will include an inbound field set to true if the connection is inbound. If you have any inbound connections, then inbound connections are allowed.

If you don’t have inbound connections, please read instructions for enabling inbound connections.

Enabling Connections

If Bitcoin Core can’t automatically configure your router to open port 8333, you will need to manually configure your router. We’ve tried to make the following instructions generic enough to cover most router models; if you need specific help with your router, please ask for help on a tech support site such as SuperUser.

Enabling inbound connections requires two steps, plus an extra third step for firewall users:

1. Giving your computer a static (unchanging) internal IP address by configuring the Dynamic Host Configuration Protocol (DHCP) on your router.

2. Forwarding inbound connections from the Internet through your router to your computer where Bitcoin Core can process them.

3. Configuring your firewall to allow inbound connections. This step mainly applies to Windows users, as Mac OS X and most Linuxes do not enable a firewall by default.

Configuring DHCP

In order for your router to direct incoming port 8333 connections to your computer, it needs to know your computer’s internal IP address. However, routers usually give computers dynamic IP addresses that change frequently, so we need to ensure your router always gives your computer the same internal IP address.

Start by logging into your router’s administration interface. Most routers can be configured using one of the following URLs, so keep clicking links until you find one that works. If none work, consult your router’s manual.

• http://192.168.0.1 (some Linksys/Cisco models)

• http://192.168.1.1 (some D-Link/Netgear models)

• http://192.168.2.1 (some Belkin/SMC models)

• http://192.168.123.254 (some US Robotics models)

• http://10.0.1.1 (some Apple models)

Upon connecting, you will probably be prompted for a username and password. If you configured a password, enter it now. If not, the Router Passwords site provides a database of known default username and password pairs.

After logging in, you want to search your router’s menus for options related to DHCP, the Dynamic Host Configuration Protocol. These options may also be called Address Reservation. For example, the router page shown below calls the option we need “DHCP Reservation”:

DHCP reservation button

In the reservation configuration, some routers will display a list of computers and devices currently connected to your network, and then let you select a device to make its current IP address permanent:

Easy DHCP reservation

If that’s the case, find the computer running Bitcoin Core in the list, select it, and add it to the list of reserved addresses. Make a note of its current IP address—we’ll use the address in the next section.

Other routers require a more manual configuration. For these routers, you will need to look up the fixed address (MAC address) for your computer’s network card and add it to the list. This operation differs by operating system:

• Windows 7 & 8: Press Win-R (Windows key plus the R key) to open the Run dialog. Type cmd to open the console. Type ipconfig /all and find the result that best matches your connection—usually a wireless connection. Look for a line that starts with “Physical Address” and contains a value like this:

    Physical Address. . . . . . . . . : 01-23-45-67-89-AB

  Replace all the dashes with colons, so the address looks like this: 01:23:45:67:89:AB. Use that address in the instructions below.

• Linux: open a terminal and type ifconfig. Find the result that best matches your connection—a result starting with wlan indicates a wireless connection. Find the field that starts with HWaddr and copy the immediately following field that looks like 01:23:45:67:89:ab. Use that value in the instructions below.

• Mac OS X: open a terminal and type ifconfig. Find the result that best matches your connection—a result starting with en1 usually indicates a wireless connection. Find the field that starts with ether: and copy the immediately following field that looks like 01:23:45:67:89:ab. Use that value in the instructions below.

Once you have the MAC address, you can fill it into your router’s manual DHCP assignment table, as illustrated below. Also choose an IP address and make a note of it for the instructions in the next subsection. After entering this information, click the Add or Save button.

Manual DHCP reservation

Then reboot your computer to ensure it gets assigned the address you selected and proceed to the Port Forwarding instructions below.

Port Forwarding

For this step, you need to know the local IP address of the computer running Bitcoin Core. You should have this information from configuring the DHCP assignment table in the subsection above.

Login to your router using the same steps described near the top of the DHCP subsection. Look for an option called Port Forwarding, Port Assignment, or anything with “Port” in its name. On some routers, this option is buried in an Applications & Gaming menu.

The port forwarding settings should allow you to map an external port on your router to the “internal port” of a device on your network as shown in the screenshot below.

Port forwarding

Both the external port and the internal port should be 8333 for Bitcoin. (You may also want to map port 18333 for Bitcoin’s testnet, although this guide does not cover using testnet.) Make sure the IP address you enter is the same one you configured in the previous subsection.

After filling in the details for the mapping, save the entry. You should not need to restart anything. Start Bitcoin Core (if you haven’t already) and follow the Testing Connections instructions to test your connection.

If you still can’t connect and you use a firewall, you probably need to change your firewall settings. See the Firewall section below.

If something else went wrong, it’s probably a problem with your router configuration. Re-read the instructions above to see if you missed anything, search the web for help with “port forwarding”, and ask for help on sites like SuperUser.

We can’t provide direct support, but if you see a way to improve these instructions, please open an issue.

Firewall Configuration

Firewalls block inbound connections. To use Bitcoin, you need to configure your computer’s firewall to allow connections to port 8333. This is usually as easy as starting your firewall configuration software and defining a new rule to allow inbound connections to port 8333. For additional information for Windows, see the links below:

• Instructions for Windows Firewall

• Instructions for Norton Firewall

• Instructions for Mcafee Personal Firewall

Mac OS X comes with its firewall disabled by default, but if you have enabled it, see the section Allowing Specific Applications from the official Apple guide.

Ubuntu also comes with its firewall disabled by default, but if you have enabled it, see the Ubuntu wiki page for information about adding port forwarding rules.

Once you have allowed inbound connections to port 8333, start Bitcoin Core (if you haven’t already) and follow the Testing Connections instructions to test your connection.

If something else went wrong re-read the DHCP, port forwarding, and firewall instructions above to see if you missed anything, search the web for help with “port forwarding” and “opening firewall ports”, and ask for help on sites like SuperUser.

We can’t provide direct support, but if you see a way to improve these instructions, please open an issue.