Routing Updates; Ripv1; Ripv2; Ripv2 In Ripv1 Compatibility Mode - Lenovo CN4093 Application Manual

Routing Updates

RIPv1

RIPv2

RIPv2 in RIPv1 Compatibility Mode

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CN4093 Application Guide for N/OS 8.3
RIP sends routing-update messages at regular intervals and when the network
topology changes. Each router "advertises" routing information by sending a
routing information update every 30 seconds. If a router doesn't receive an update
from another router for 180 seconds, those routes provided by that router are
declared invalid. The routes are removed from the routing table, but they remain in
the RIP routes table. After another 120 seconds without receiving an update for
those routes, the routes are removed from regular updates.
When a router receives a routing update that includes changes to an entry, it
updates its routing table to reflect the new route. The metric value for the path is
increased by 1, and the sender is indicated as the next hop. RIP routers maintain
only the best route (the route with the lowest metric value) to a destination.
For more information see The Configuration Menu, Routing Information Protocol
Configuration in the Lenovo N/OS Command Reference.
RIP version 1 uses broadcast User Datagram Protocol (UDP) data packets for the
regular routing updates. The main disadvantage is that the routing updates do not
carry subnet mask information. Hence, the router cannot determine whether the
route is a subnet route or a host route. It is of limited usage after the introduction of
RIPv2. For more information about RIPv1 and RIPv2, refer to RFC 1058 and
RFC 2453.
RIPv2 is the most popular and preferred configuration for most networks. RIPv2
expands the amount of useful information carried in RIP messages and provides a
measure of security. For a detailed explanation of RIPv2, refer to RFC 1723 and
RFC 2453.
RIPv2 improves efficiency by using multicast UDP (address 224.0.0.9) data packets
for regular routing updates. Subnet mask information is provided in the routing
updates. A security option is added for authenticating routing updates, by using a
shared password. Lenovo N/OS supports using clear password for RIPv2.
Lenovo N/OS allows you to configure RIPv2 in RIPv1compatibility mode, for
using both RIPv2 and RIPv1 routers within a network. In this mode, the regular
routing updates use broadcast UDP data packet to allow RIPv1 routers to receive
those packets. With RIPv1 routers as recipients, the routing updates have to carry
natural or host mask. Hence, it is not a recommended configuration for most
network topologies.
Note: When using both RIPv1 and RIPv2 within a network, use a single subnet
mask throughout the network.