Ericsson ECN330 - Page 430

Configuring the ECN330-switch
424 1553-KDU 137 365 Uen D 2006-06-16
6.20.9 Configuring the Routing Information Protocol
The RIP protocol is the most widely used routing protocol. The RIP protocol
uses a distance-vector-based approach to routing. Routes are determined on
the basis of minimizing the distance vector, or hop count, which serves as a
rough estimate of transmission cost. Each router broadcasts its advertisement
every 30 seconds, together with any updates to its routing table. This allows all
routers on the network to learn consistent tables of next hop links which lead to
relevant subnets.
Figure 187 Configuring RIP
Command Usage
• Just as Layer 2 switches use the Spanning Tree Algorithm to prevent
loops, routers also use methods for preventing loops that would cause
endless retransmission of
data traffic. RIP utilizes the following three
methods to prevent loops from occurring:
• Split horizon – Never propagate routes back to an interface port
from which they have been acquired.
• Poison reverse – Propagate routes back to an interface port from
which they have been acquired, but set the distance-vector metrics
to infinity. (This provides faster convergence.)
•
Triggered updates – Whenever a route gets changed, broadcast an
update message
after waiting for a short random delay, but without
waiting for the periodic cycle.
• RIP-2 is a compatible upgrade to RIP. RIP-2 adds useful capabilities for
plain text authentication, multiple independent RIP domains, variable
length subnet masks, and multicast transmissions for route advertising
(RFC 1723).
A
1
3
6
4
2
5
BC
DE
A
A
B
C
D
Link Cost
0
E
1
1
3
1
0
1
2
1
2
Cost = 1 for all links
Routing table for node A