Installing and Administering Internet Services

Chapter 8 321

Conﬁguring gated

Overview

A router is a device that has multiple network interfaces and transfers

Internet Protocol (IP) packets from one network or subnet to another

within an internetwork. (In many IP-related documents, this device is

also referred to as a “gateway.” The term “router” is used in this chapter.)

The gated daemon updates routing tables in internetwork routers.

Developed at Cornell University, gated handles the RIP, EGP, BGP, and

OSPF routing protocols and the Router Discovery Protocol (RDP), or any

combination of these protocols.

Routing protocols are designed to ﬁnd a path between network nodes. If

multiple paths exist for a given protocol, the shorter paths are usually

chosen. Each protocol has a cost or a metric that it applies to each path.

In most cases, the lower the cost or metric for a given path, the more

likely a protocol will choose it.

When started, gated reads the kernel routing table on the local machine.

gated maintains a complete routing table in the user space, and keeps

the kernel routing table (in the kernel space) synchronized with this

table.

In large local networks, there are often multiple paths to other parts of

the local network. gated can be used to maintain near optimal routing to

the other parts of the local network, and to recover from link failures in

paths.

Advantages

Using gated offers these advantages:

• Dynamic routing eliminates the need to reset routes manually. When

network failures occur, routes are automatically re-routed.

• Dynamic routing makes it easier to add and administer nodes.

• Dynamic routing lowers the cost of operating complex internet

systems.

• gated translates among several protocols,passing information within

or between IP routing domains or autonomous systems.

“Autonomous system” is used here to refer to a group of connected

nodes and routers in the same administrative domain that are