So you have made the effort of putting an antenna onto your roof, made the connection to your local AP and got either a coax run to a wireless card in your computer or a ethernet run back from the waterproofed AP on your roof. How do you make sure that all the other machines in your house can use this network too?
There is no single answer to this question that is correct, it all depends on your level of knowledge or how much effort you want to go to.
NAT: Network address translation
The internet gateway: typically a hardware ADSL router
One of the most simple ways of getting the rest of your computers on the network is by using network address translation. YOu are probably already using it to get a number of computers on your home LAN connected to the internet concurrently. How this works is you allow one machine on the gateway to the internet to translate from a real world IP to a private address range typically 192.168.x.y. At first I used the private range 192.168.0.0/24 which mean that all the IPs 192.168.0.0 to 192.168.0.255 could be used by my home network and connected to the internet thought my real bigpond address 144.136.177.192, using windows this can be achieve using internet connection sharing.
The wireless gateway: typically a machine with two network interfaces, one to the LAN one to the air-stream mesh.
Using the same philosphy the machine connected to the air-stream AP has its routed wireless mesh address 10.121.0.2 but it also has an internal LAN address in my example 192.168.0.3. It uses the same principal that the internet gateway router usings by sharing this one address among the other machines in my private range.
For this to work we need to do a couple of things. If my internet gateway is 192.168.0.1 then the default route for all my LAN machines will be 192.168.0.1 eg IP 192.168.0.4 netmask 255.255.255.0 gateway 192.168.0.1 DNS 61.9.224.15 (or whatever your ISP suggests). What we can do is put a static route in the machine at 192.168.0.1 to send all traffic bound for the Air-Stream wireless lan (10.96.0.0/11, 10.96.0.0 netmask 255.224.0.0) to be diverted to 192.168.0.3 which has a connection to teh rest fo the air-stream wan.
In the same way that NAT is applied to the internet connection it is also applied to the wireless LAN connection.
The reason NAT provides you with a certain amount of security as you are hiding on an address range that other cannot access but only connection that are requested by you are allowed through.
Dynamic Routing
In order to keep track of all the different ways that traffic can flow around the air-stream mesh a type of advanced routing known as dynamic routing. Where all the parameters regarding the topology of the network are given to a network daemon and it works out the best route to take based on these parameters. As the network grows it becomes more reliant on the dynamic routing to find alternative routes, this would need to be updated by hand on a number of routers if it were to be done by hand.
Border Gateway Protocol (BGP)
The type of routing that is used by Air-Stream is called border gateway protocol, it allows for filtering of routes and instant updates that OSPF and RIP do not allow.
/27 Routed Network using BGP
This allows us to make use of the 32 IPs all network users are entitled to!
If you are technically inclined the idea of using NAT may seems like a waste, as one of the advantages of being part of the WAN is that we have lots of IPs for everybody, unlike the internet which has largely run out of IP real estate.
If you want to advertise your subnet yourself you will need to run the network suite zebra or quagga (preffed) on a Unix, Linux or BSD operating system. Or if you have access to a windows 2003 server it can also run these protocols as can Cisco IOS based routers.
Alternatively you may be able to make arrangements with your AP administrator that they can keep the routing records as part of thier AP and you will only need to prepare a couple of static routes on your end.
Sorry if this is a bit of a glossary more details about dynamic routing can be found on www.quagga.net
Firewalling
Once your machines are routed onto the wireless network you may want to think about firewalling to keep your computers in and to keep unwanted packets out. This should all be done on the same machine that is doing the routing.
Sam Hodge
It is preferable that people be as self sufficent as possible, because the network administrators are under enough load as it is.
If all of this routing stuff is of interest to you I suggest you offer to lend the network administrators a hand or write a brief how-to on the Air-Stream site.
