Technical data

Conﬁguring Routing

Routing allows trafﬁc from your local network to reach its destination elsewhere

on the internet. Hosts and gateways on a network use routing protocols to

exchange and store routing information. Routing is the act of forwarding

datagrams based on information stored in a routing table.

The TCP/IP Services product provides two types of routing: static and dynamic.

This chapter reviews key routing concepts and describes:

• How to conﬁgure static routes (Section 4.2)

• How to enable and disable dynamic routing (Section 4.3)

• How to conﬁgure GATED (Section 4.4)

4.1 Key Concepts

If the hosts on your network need to communicate with computers on other

networks, a route through a gateway must be deﬁned. All hosts and gateways

on a network store information about routes in routing tables. With TCP/IP

Services, routing tables are maintained in both dynamic and permanent memory.

You can deﬁne routes manually (static routing), or you can enable routing

protocols that exchange information and build routing tables based on the

information exchanged (dynamic routing).

4.1.1 Static Routing

Because static routing requires manual conﬁguration, it is most useful when the

number of gateways is limited and where routes do not change frequently. For

information on manually conﬁguring routing, see Section 4.2.

4.1.2 Dynamic Routing

Complex environments require a more ﬂexible approach to routing than a static

routing table provides. Routing protocols distribute information that reﬂect

changing network conditions and update the routing table accordingly. Routing

protocols can switch to a backup route when a primary route becomes unavailable

and can determine the best route to a given destination.

Dynamic routing tables use information received by means of routing protocol

updates; when routes change, the routing protocol provides information about the

changes.

Routing daemons implement a routing policy, that is, the set of rules that

specify which routes go into the routing table. A routing daemon writes routing

messages to a routing socket, causing the kernel to add a new route, delete an

existing route, or modify an existing route.

The kernel also generates routing messages that can be read by any routing

socket when events occur that may be of interest to the process, for example, the

interface has gone down or a redirect has been received.

Conﬁguring Routing 4–1