This page is a guide to help users of Bittorrent and Apple Airport Extreme to configure their Apple Airport Extreme Base Station (AEBS) and Apple Macintosh computer for firewall port forwarding. The Apple Airport Extreme Base Station includes a built-in firewall that will decrease your Bittorrent download speeds unless you enable port forwarding to your Mac.

If you aren't certain that you are firewalled, if you properly configure your base station but still have slow downloads, or if you are on a non-AEBS network, you may want to go directly to What if my Bittorrent downloads are still slow? for a list of other reasons that may cause your Bittorrent downloads to be slow.

This guide was written based on a configuration of Comcast digital cable connected to the AEBS, with IP address(es) supplied to the AEBS via DHCP from Comcast. The AEBS transmits to an Apple Airport Extreme card installed in the Mac. This guide assumes your built-in OS X Firewall (System Preferences>Sharing>Firewall) is OFF.

Airport Extreme Network Configuration

Technical Note (purely informational, ignore if you like): Notice how the other selection, "Share a range of IP addresses", provides a default beginning address of 10.0.1.2 and an ending address of 10.0.1.200. This range of addresses is used by the AEBS to provide IP addresses to computers on the local network via DHCP. Our Mac will be using a manual IP address (NOT DHCP), so we will have to pick an address outside of this range for the manual IP address of the Mac (see step 2 below).

2. Configuration of the Mac's network (System Preferences>Network) - We want our Mac to use a STATIC IP address. That is, we want it to always have the same IP address every time we turn it on. Therefore, we must set a manual IP address for the Mac. Since the AEBS is already using the addresses from 10.0.1.2 to 10.0.1.200 (see step 1 above), we have to pick a number higher than 10.0.1.200 (but less than 10.0.1.255). We'll use 10.0.1.201 for this example. Feel free to use the same IP address at home. Set the Mac's IP address to manual and enter the IP address, subnet, router and DNS server as shown. Click Apply Now to save the settings.

3. Configuration of the Apple Airport Extreme Base Station Port Forwarding - Now everything is working; you can get to the internet and even download torrents, but you are still firewalled by the AEBS. We have to set port forwarding to allow access through the AEBS to the appropriate ports on the Mac. We have to tell the AEBS which IP address is allowed to receive the port forwarding and which ports to forward. Setting ports 6881 through 6889 to forward to the same ports at IP address 10.0.1.201 (as set in step 2, above) tells the AEBS to allow connections through those ports, for our Mac with IP address 10.0.1.201. After setting these port forwards and updating the AEBS configuration, you should no longer be firewalled, your download speeds will increase, and other Bittorrent users will like you a lot more.

What if my Bittorrent downloads are still slow?

• Do you have a fast connection to the internet? Bittorrent can be fast, but you still download the same amount of data. If you are using dial-up, don't expect cable modem speeds.
• Is the torrent fast for others? If a seeder has a slow upload speed or is firewalled, there is no way you can make it faster. Check other torrents to see if your speed increases.
• Are you running a software firewall? Make sure any firewalls on your computer are turned off. Consult online help, read the manual, or contact your computer support center if you do not know how to check.
• Is there another firewall? You may configure your local network properly for port mapping, but your cable or DSL modem or ISP may still have a firewall between you and other peers. You may need to check the configuration of your modem or talk to your internet service provider to see if they automatically block Bittorrent ports.
• Are you uploading at your maximum upload speed? If you are uploading at your maximum bandwidth, downloading files or surfing the internet will slow dramatically. My maximum download speed is over 300 k/sec, but my maximum upload speed is only 30 k/sec. If I am uploading at much over 20 k/sec, my Bittorrent download speed drops way down and web surfing becomes unbearably slow. Many Bittorrent clients provide the ability to set your maximum upload bandwidth to avoid this problem. Leave at least 10 k/sec below your maximum upload speed to increase your download speed.

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