Routers - Routing Protocols

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Introduction

The Solaris operating environment supports two routing protocols: Routing Information Protocol (RIP) and ICMP Router Discovery (RDISC). RIP and RDISC are both standard TCP/IP protocols.

Routing Protocols

RIP is implemented by in.routed, the routing deamon, which automatically starts when the machine boots. When run on a router with the s option specified, in.routed fills the kernel routing table with a route to every reachable network and advertises "reachability" through all network interfaces.

When run on a host with the q option specified, in.routed extracts routing information but does not advertise reachability. On hosts, routing information can be extracted in two ways:

• Do not specify the s flag (capital "S": "Space-saving mode") and in.routed builds a full routing table exactly as it does in a router.
• Specify the s flag and in.routed creates a minimal kernel table, containing a single default route for each available router.

ICMP Router Discovery (RDISC) Protocol

Hosts use RDISC to obtain routing information from routers. Thus, when hosts are running RDISC, routers must also run another protocol, such as RIP, in order to exchange router information amoung themselves.

RDISC is implemented by in.rdisc, which should run on both routers and hosts. Normally, when in.rdisc runs on a host, it enters a default route for each router that is also running in.rdisc. A host that is running in.rdisc can not discover routers that are running only RIP. Furthermore, when routers are running in.rdisc (rather than in.routed), then can be configured to have a different preference, which causes hosts to select a better router.