Installing and Administering LAN/9000 Software

164 Chapter6

Network Addressing

Conﬁguring Gateways on Variable-Length Subnets

Conﬁguring Gateways on Variable-Length

Subnets

Besides using the appropriate subnet masks, each gateway needs to be

conﬁgured so that it can properly route messages among the several

subnet works. Following are descriptions of two types of routing: explicit

routing and dynamic routing. When using explicit routing, you must

specify the IP address of each gateway to which you are directly

connected. When using dynamic routing, you need to specify only the IP

address of one gateway, and the system learns the IP address of other

gateways from the speciﬁed gateway.

Explicit Routing

There are many ways to set up routing. For example, you might add the

following entries to the netconf ﬁle on Host A in Figure 6-15:

ROUTE_DESTINATION[0]=”net 192.6.12.192”

ROUTE_MASK[0]=”255.255.255.224”

ROUTE_GATEWAY[0]=”192.6.12.130”

ROUTE_COUNT[0]=”1”

ROUTE_DESTINATION[1]=”net 192.6.12.33”

ROUTE_MASK[1]=”255.255.255.240“

ROUTE_GATEWAY[1]=”192.6.12.131”

ROUTE_COUNT[1]=”1”

ROUTE_DESTINATION[2]=”net default”

ROUTE_MASK[2]=””

ROUTE_GATEWAY[2]=”192.6.12.132”

ROUTE_COUNT[2]=”1”

The 1 in each ROUTE_COUNT entry speciﬁes an indirect route. For

example, messages for the system on the 192.6.12.32 subnetwork will

ﬁrst be sent to Host B (192.6.12.131), and from there they will be

forwarded to the destination system.

Dynamic Routing

Alternatively, and perhaps the easiest way to manage growth on the

192.6.12 network, you might add the following entries to each netconf

ﬁle.