The Linux TCP/IP server configuration page

IP routing at ON0BAF

• Routing for Germany: first a host route to db0pra.ampr.org is defined, which is accessible directly from the AX.25 interface through FlexNet routing; next all traffic for Germany (network 44.130.0.0, where the first two octets are considered network identification) is routed through db0pra.ampr.org.
  ax0 host 44.130.20.50
  ax0 net 44.130.0.0 netmask 255.255.0.0 gw 44.130.20.50
• Routing for Oudenaarde (oud.be.ampr.org). As for Germany, we first define a host route to the IP-router of Oudenaarde (on0ob), which is directly accessible through FlexNet routing. Next, a network route to oud.be.ampr.org is defined (network 44.144.152.0 with the first 3 octets considered network identification) through IP-router on0ob. For geographical optimization, we also added a route to all regions in provincy West-Vlaanderen through IP-router on0ob. Regions in West-Vlaanderen are assigned IP-addresses with values 160 to 167 in the third octet (binary: 10100000 to 10100111, from which we notice the 5 most significant bits - 10100 - are common. If we define a netmask of 128+64+32+16+8 - being 248, we say only the five most significant bits attribute to network identification: all IP addresses from 44.144.160.0 to 44.144.167.255 will then be considered part of the same network and will be elegible for the route below.
  ax0 host 44.144.152.1
  ax0 net 44.144.152.0 netmask 255.255.255.0 gw 44.144.152.1
  ax0 net 44.144.160.0 netmask 255.255.248.0 gw 44.144.152.1
• Now, some routes in Limburg: within our own provincy, we optimize explicit routes to the known regions. The story is still the same (first NOL, then DPP):
  ax0 host 44.144.179.1
  ax0 net 44.144.179.0 netmask 255.255.255.0 gw 44.144.179.1
  ax0 host 44.144.50.4
  ax0 net 44.144.180.0 netmask 255.255.255.0 gw 44.144.50.4
• Regions that are not assigned in our own provincy, will be dumped on a local interface to avoid ping-pong forwarding (story for network identification looks familiar to what we said about West-Vlaanderen). Notice that this route will not dump all traffic for Limburg to a local interface! IP searches best-match first (meaning, first an accurate host route is searched for, then network routes from most accurate to least accurate, and finally a default route is searched for). So, the IP addresses that didn't match the 2 regions NOL and DPP (and our own of course), fall through to this route:
  ax0 net 44.144.176.0 netmask 255.255.248.0
• Once more the same story for all regions in Liège and - why not - a geographical optimization towards all regions in Luxemburg. For Liège, notice the value of 240 for the third octet of the netmask. Regions in Liège are assigned values between 208 and 223 in the third octet (binary: 11010000 to 11011111, the 4 most significant bits being common: 128+64+32+16).
  ax0 host 44.144.208.1
  ax0 net 44.144.208.0 netmask 255.255.240.0 gw 44.144.208.1
  ax0 net 44.144.240.0 netmask 255.255.248.0 gw 44.144.208.1
• And now the fall-through route for all ampr.org traffic, that wasn't matched to the entries before, through our nearby HAM-gateway (netmask now simply indicates the entire class A network):
  ax0 host 44.144.0.1
  ax0 host 44.144.220.1
  ax0 net 44.0.0.0 netmask 255.0.0.0 gw 44.144.0.1