Technical data

BLADE OS 5.1 Application Guide
BMD00136, November 2009 Chapter 9: Routing Information Protocol
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RIP Features
BLADE OS provides the following features to support RIPv1 and RIPv2:
Poison
Simple split horizon in RIP scheme omits routes learned from one neighbor in updates sent to that
neighbor. That is the most common configuration used in RIP, that is setting this Poison to
DISABLE. Split horizon with poisoned reverse includes such routes in updates, but sets their
metrics to 16. The disadvantage of using this feature is the increase of size in the routing updates.
Triggered Updates
Triggered updates are an attempt to speed up convergence. When Triggered Updates is enabled,
whenever a router changes the metric for a route, it sends update messages almost immediately,
without waiting for the regular update interval. It is recommended to enable Triggered Updates.
Multicast
RIPv2 messages use IP multicast address (224.0.0.9) for periodic broadcasts. Multicast RIPv2
announcements are not processed by RIPv1 routers. IGMP is not needed since these are inter-router
messages which are not forwarded.
To configure RIPv2 in RIPv1 compatibility mode, set multicast to disable, and set version to
both.
Default
The RIP router can listen and supply a default route, usually represented as 0.0.0.0 in the routing
table. When a router does not have an explicit route to a destination network in its routing table, it
uses the default route to forward those packets.
Metric
The metric field contains a configurable value between 1 and 15 (inclusive) which specifies the
current metric for the interface. The metric value typically indicates the total number of hops to the
destination. The metric value of 16 represents an unreachable destination.