Configuring Rip; Overview; Rip Route Entries; Rip Timers - HPE FlexNetwork HSR6800 Configuration Manual

Configuring RIP

Routing Information Protocol (RIP) is a distance-vector simple interior gateway protocol suited to
small-sized networks. It employs UDP to exchange route information through port 520.

Overview

RIP uses a hop count to measure the distance to a destination. The hop count from a router to a
directly connected network is 0. The hop count from a router to a directly connected router is 1. To
limit convergence time, RIP restricts the metric range from 0 to 15. A destination of a metric value of
16 (or greater) is considered unreachable. For this reason, RIP is not suitable for large-sized
networks.

RIP route entries

RIP stores routing entries in a database. Each routing entry contains the following elements:
•
Destination address—IP address of a destination host or a network.
•
Next hop—IP address of the next hop.
•
Egress interface—Egress interface of the route.
•
Metric—Cost from the local router to the destination.
•
Route time—Time elapsed since the last update. The time is reset to 0 every time the routing
entry is updated.
•
Route tag—Used for control routes. For more information, see "Configuring routing policies."

RIP timers

RIP uses the following timers:
•
Update timer—Specifies the interval between route updates.
•
Timeout timer—Specifies the route aging time. If no update for a route is received within the
aging time, the metric of the route is set to 16.
•
Suppress timer—Specifies the duration a RIP route stays in suppressed state. When the
metric of a route is 16, the route enters the suppressed state. A suppressed route can be
replaced by an update route that is received from the same neighbor before the suppress timer
expires and has a metric less than 16.
•
Garbage-collect timer—Specifies the interval from when the metric of a route becomes 16 to
when it is deleted from the routing table. RIP advertises the route with a metric of 16. If no
update is announced for that route before the garbage-collect timer expires, the route is deleted
from the routing table.

Routing loop prevention

RIP uses the following mechanisms to prevent routing loops:
•
Counting to infinity—A destination with a metric value of 16 is considered unreachable. When
a routing loop occurs, the metric value of a route will increment to 16 to avoid endless loopings.
•
Split horizon—Disables RIP from sending routing information on the interface from which the
information was learned to prevent routing loops and save bandwidth.
20