HP-UX LAN Administrator's Guide (Feburary 2007)

Network AddressingDRAFT COPY
Configuring Gateways on Variable-Length Subnets
Chapter 7130
ROUTE_DESTINATION[0]=”net 192.6.12.64”
ROUTE_MASK[0]=”255.255.255.192”
ROUTE_GATEWAY[0]=”192.6.12.129”
ROUTE_COUNT[0]=”1”
ROUTE_DESTINATION[1]=”net 192.6.12.192”
ROUTE_MASK[1]=”255.255.255.224”
ROUTE_GATEWAY[1]=”192.6.12.130”
ROUTE_COUNT[1]=”1”
ROUTE_DESTINATION[2]=”net 192.6.12.32”
ROUTE_MASK[2]=”255.255.255.240”
ROUTE_GATEWAY[2]=”192.6.12.34”
ROUTE_COUNT[2]=”1”
ROUTE_DESTINATION[3]=”default”
ROUTE_GATEWAY[3]=”192.6.20.1”
ROUTE_COUNT[3]=”0”
If you add a new subnetwork to the Facility LAN at a later time, you will need to add only an
appropriate routing entry on Host D. It will not be necessary to configure the other subnet
gateways A, B, and C.
With this configuration, each subnet gateway (Hosts A, B, and C) will initially route messages
for a system outside its subnet to Host D. The subnet gateway, however, will learn of the more
direct routes automatically when Host D redirects the messages to one of the other subnet
gateways. Subsequent messages for the destination system will be routed directly to the
appropriate subnet gateway.
For example, referring to Figure 7-14, suppose messages are sent from system A1
(192.6.12.67) to system B1 (192.6.12.34). The first message will actually be routed to Host D
(through Host A). Host D then will redirect the message through Host B. At the same time,
Host D will notify Host A that Host B is a more direct route for messages to system B1.
Subsequent messages to system B1 will be routed directly from Host A to Host B.
Redirected routes are called dynamic routes. You can see these dynamic routes by executing
the command netstat -rv on Host A. Dynamic routes are indicated in the display by a D
flag.
Proxy ARP Server
The default direct route entry on Host D assumes that there is a proxy ARP server on the
192.6.20 network. If there is none, additional indirect route entries can be configured for each
gateway that is directly connected to the 192.6.20 network.
For example, referring to Figure 7-14, you might add the following indirect routes to send
messages to Division 2 and Division 3.