Configuring Windows for TOR

Windows has three internal tables which it uses to direct TCP/IP data to the correct network adapter and to the correct remote computer:

The ARP Table entries are probably the most critical for TCP/IP over radio (TOR) clients and gateways, but entries in the other two tables can be useful in some situations.

1. ARP Table

AGWPE's TOR feature uses Windows' ARP entries to associate a station's IP address with that station's ham radio callsign.

For example, let's assume the remote station you want to contact has an IP address of 44.1.1.8 and a callsign of SV2AGW-8. Let's say you want to send an email via SV2AGW-8's gateway. You've already told Window to use SV2AGW-8 as your internet gateway when you configured the TOR adapter, but the configuration process required you to use SV2AGW-8's IP address, 44.1.1.8, not his callsign. However, AGWPE can't send a packet to an IP address; it needs to send it to a ham radio callsign. To determine the callsign for 44.1.1.8. AGWPE will look in the Windows's ARP table to see if there is an entry that translates that IP address to a callsign.

The problem is that when Windows first boots up, the ARP table is always cleared and empty. Windows begins to rebuild a fresh table of IP address=callsign entries based on network exchanges it observes,

If AGWPE finds there is not yet an ARP entry for an IP address it needs, AGWPE sends out request packet to "QST" asking for the station using the destination IP address, 44.1.1.8, to respond with its ham callsign. If a response comes back (it might not! ), the IP address=callsign entry is put in the Windows ARP table. From then on during that computer session, AGWPE knows which callsign to use when addressing packets to 44.1.1.8 .

To speed-up the ARP table re-building process, you can enter IP address=callsign information in the ARP table as part of the computer boot-up process or when you first start AGWPE. You can do that with a DOS batch file.

Each ARP entry includes an internet address and a hex physical address (call sign and radioport). In order to calculate the correct hex address for a station, use the free AGWsoft utility AGWARP.EXE You can download this in zip format from: the AGW Programs page on this site.

The utility will then return a hex physical address. For the example above it would be ab:ac:0d:2c:44:86 . Finally it returns a closing message, such as "Type now <ARP -s 41.1.1.8 ab:ac:0d:2c:44:86>". Rather than typing that, write down everything in between the brackets < > and then press the Return key to close the utility. If you need physical addresses for any other stations, you will need to re-run the utility .

Note: The ARP entry can also be used to tell AGWPE to use particular radioport to contact this callsign. Normally AGWPE uses the default port that you specified on the TOR configuration screen under Setup Routes. The ability to specify a different port can be useful if a contact should be made on alternative an radioport / frequency.

Open a DOS-prompt box (Start: Run: CMD) and type EDIT ARPROUTE.BAT (or another .bat name of your choice). If there is no existing file with that name, the edit program will create a new file named ARPROUTE.BAT with no data in it.

On a blank line in the edit window, enter an ARP entry, i.e. the information you wrote down from the AGWARP utility, except replace any colons (:) in the physical IP address with dashes (-). For example:
ARP -s 41.1.1.8 ab-ac-0d-2c-44-86

If you have other ARP entries, add each on a separate line. When done, save the file to a folder of your choice, making note of the path. Test the file by double clicking on its icon and make sure no error messages occur.

You can also see the ARP table and your new entry by opening a DOS-prompt box (Start: Run: CMD) and at the DOS prompt enter: ARP -a [You can also manually enter ARP entries from the DOS prompt instead of a batch file.]

From the AGWPE's menu, select Startup Programs. Use the ADD button to navigate to and select the ARPROUTE.BAT file you created. Once entered into the auto start application list, the file will run each time AGWPE starts up and it will put your ARP entries into the Windows ARP table.

Alternatively, you could have it run each time Windows boots by placing it in the Startup Folder ( C:\Windows\Start Menu\Programs\Startup in Windows 95, 98, or ME, or C:\Documents and Settings\All Users\Start Menu\Programs\Startup in Windows XP).

2. IP ROUTE Table

The IP Routing Table helps Windows decide which network adapter to use to send a TCP/IP packet. Its choices might be the SV2AGW TOR virtual adapter, the hardware network interface card (if one exists), or back to your own computer via a loop back port. For many users, no additions to the IP Routing table will be necessary, however, in some cases, Routing Table additions will help your TOR communications.

By default, Windows will build the Routing Table anew at each reboot. Its primary source of information is the Internet Protocol (TCP/IP) property settings of your network adapters, including the SV2AGW TOR adapter. The key information is the IP address assigned to the adapter. If you also have a hardware network card installed, Windows will make that IP address the default gateway adapter, but the IP address of your SV2AGW TOR adapter will create a special route for your ham radio network (those would be addresses that begin with 44, assuming you are using an IP address yourself that begins with 44).

For example, say your settings for the SV2AGW TOR adapter looked like this example ...

An entry is automatically placed in the IP Routing table indicating that any IP packet with a destination IP addresses beginning with 44 should be routed to your SV2AGW TOR adapter at IP address 44.128.34.2 (and then onto your gateway station at 44.128.6.1).

Why 44? That's determined by the subnet mask values under the four octets (44, 128, 34, and 2) in the IP Address. A subnet mask value of 255 means "match all the binary digits of the octet above"; a value of 0 means "no need to match any of these digits". In our example, only the first octet, 44, has a subnet mask value of 255. The other octets have a mask value of 0. So the Routing table will contain an entry that says, in essence, send all destination IP addresses beginning with 44 to the 44.128.34.2 adapter.

[For addresses that don't begin with 44, Windows will use the Routing Table to determine the correct routing. For example, if you also have a network card in your computer, then the Routing Table will suggest that packets for all non-44 addresses should be routed to that network card and directly to the internet or wired network and not to the SV2AGW TOR adapter. (If you don't have a network card installed, then the Routing Table will send packets go to the SV2AGW TOR adapter.)]

Communicating with radio stations that don't use a "44" address

If your computer has both a network card and the TOR adapter installed and you will contact stations using TOR that don't have an IP address beginning with 44, then you should add them to the Routing Table so that packets are sent to them via the SV2AGW TOR adapter and not the network card. The easiest way to do this is to add those routes into the batch file created for ARP entries (see above, Create an ARP Entry Batch File) or create a batch file as above if one doesn't exit.

To add a route to the IP Routing Table using your ARP Entry Batch file, enter a new line that begins with ROUTE ADD followed by the full IP address of the remote station followed by the IP address chosen for your SV2AGW TOR adapter (your IP address), for example:

ROUTE ADD 133.275.12.6 44.128.34.2

This tells windows to route any IP packets addressed to 133.275.12.6 to the SV2AGW TOR adapter at 44.128.34.2. Of course you would replace the number in green with the address of your distant station and replace the number in red with your SV2AGW TOR adapter's address (your ham radio IP address).

To add a route without using a batch file, open a DOS-prompt box (Start: Run: CMD) and enter your ROUTE ADD sentence as above.

To see your complete IP Route Table, enter ROUTE PRINT at a DOS prompt (Start: Run: CMD)

3. HOSTS Table

The HOSTS file can be used to help translate an IP address to a name and vice versa. For example, if you had a HOSTS table entry that said 44.0.0.2 is the same as "My Web Page", you could enter "My Web Page" as a URL address in your browser and Windows would know to go to 44.0.0.2 to find it.

This same IP Address-Name translation can be performed by a domain name server, but the HOSTS files is especially useful when a domain name service (DNS) server is not available (common on many amateur radio networks) or when you want to use an easily remembered name in place of a hard to remember IP address or lengthy domain name.

You can open the existing HOSTS file with a text editor. Instructions for adding entries to file are included in the file. [In some cases you may find only a HOSTS.SAM (sample) file and not a HOSTS file. If you do, make a copy of the HOSTS.SAM file calling it HOSTS (no extension).]

Any new entries would follow the same simple format: IP address, a space, name. For examples:

4. Ping Test

After you make your HOST, ROUTE and ARP entries, you can test them by using the Windows PING command. PING simply sends four packets to the destination station asking it to respond. PING then reports how long each response takes or, if no response is heard within a given length of time, PING reports the "request timed out".

To send the PING command, open a DOS-prompt window (Start: Run: CMD) and enter the command in this format:

PING <destination IP> <--- substitute actual IP address for <destination IP>

You can use the -w option on the ping command to increase the time PING waits for a response (default is 1 second). For example, to wait for each response for 5 seconds (5000 milliseconds), use -w 5000. e.g. PING 44.0.0.1 -w 5000

If you get a reply with a response time, then all Windows applications using TCP/IP, i.e. Internet Explorer, Outlook Express, will also be able to communicate with the PING-ed destination. If all four requests time out, then Windows is not hearing a response from the destination IP and it is useless to try any other TOR applications.

5. Diagnosing Routing Problems

Download and use the AGWTerminal program and watch the packets that AGWPE is sending when you execute the PING command. They should look like this:

Sound Card Packet with AGWPE