A Network Address is used for routing purposes, and is derived from
a block of IP addresses used in
a particular sub-network. Here's a brief explanation
of the sub-net concept as it relates here.
You'll notice that you and your neighbors have similar IP addresses. For example, the Green Bay area IP addresses range from 44.92.20.1 to 44.92.20.254. They all have a common element to their addresses - the dotted number combination of 44.92.20. When referring to the Local Network Address for routing purposes, it is written with a 0 at the end of this dotted number combination.
For example, the Green Bay Local Network Address shown above is written as 44.92.20.0. When entering the IPBroadcast address in the node, you will need to be in the sysop mode and you'll enter the local sub-net's Network Address. The command syntax is:
IPBroadcast (local network address)
In the case of our Green Bay example we used above, this would be:
In order to effectively route IP packets, we need to use 2 forms of the IPROUTE command. One is intended for individual hosts with their own IP addresses. The IPROUTE command syntax would look like this to enter a specific host with it's unique IP address:
IPROUTE (Destination IP Address) (+) (Port 0 or 1) (Gateway IP, if used)
Let's say we have a station with an IP address of 44.92.130.10. It is on port 0, the radio port. We wish to add this, but need to use 44.92.130.9 to get to the 44.92.130.10 host. First, we need to enter a route to the gateway, or relaying station address. In this case, our IPROUTE command would look like this:
The other IP routing task is meant for accessing other networks, represented by blocks of IP addresses and the number of significant bits. Here is a brief explanation of networks and the number of significant bits.
First off, IP addresses are, for the purposes of our discussion, 32 bits long. When you have an IP address of 123.234.123.234, each section of the address is 8 bits long. Each of the four groups of numbers separated by dots are 8 bits long. The entire IP address is 32 bits in total.
What IP routing in a node does is send IP packets to a particular place based on how many bits of the address are specified. We can specify all 32 bits - as we did in the example above - and send an IP packet to a particular station address, or we can send a group of IP addresses on to another station or node. The other station or node handles it from there.
OK, so how do we specify a particular network address block for routing purposes? Here is a guide with examples that specify the number of significant bits:
44.0.0.0 has 8 significant bits and specifies any address that begins with 44. This is the 44 network. All Amateur Packet Radio stations with IP addresses begin with 44 (except in special cases).
44.92.0.0 has 16 significant bits and specifies any address that begins with 44.92. This is the 44.92. sub-network, which is Wisconsin and the UP of Michigan.
44.92.130.0 has 24 significant bits, and specifies any address that begins with 44.92.130. This block of addresses is currently not assigned, and is only used for example purposes. It, too is a sub-network. So in order to route to a block of IP network or sub-network addresses, we use this form of the IPROUTE command:
Here's an example of how to route to the 44.92.130 block of addresses,
using 44.92.130.1 as the gateway to all other 44.92.130 series of IP addresses.
We'll be using the Radio Port 0.
We need to add a route to a gateway first, before we can route through it. We do that like this:
To remove a route to a network, we need to specify the network address, and the number of significant bits. Here's an example:
For a more complete explanation of networks and sub-networks, see the Wisconsin/UP IP coordinator's page at: www.gbonline.com/~kb9aln/4492-ip/ (currently under construction).
That's all for this part. Next month, we'll continue our alphabetical exploration of the Sysop commands for these nodes. Until then, 73 from Andy.