Nokia Network Voyager, Справочное руководство

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Voyager Reference Guide 231
vector, or Bellman-Ford, routing protocol for local networks. Routers
advertise their routes (reachability information) to other neighboring routers.
When there is information to send, a router running RIP sends updates on
each configured interface at set intervals. Each update contains paired values,
where each pair consists of an IP network address and a distance (expressed
as an integer) to that network. RIP uses a
hop count metric to measure the
distance to a destination. In the RIP metric, a router advertises directly
connected networks as a metric of 1. Networks that are reachable through one
other router are two hops, and so on. Thus, the number of hops, or hop count,
along a path from a given source to a given destination refers to the number of
gateways that a datagram would encounter along that path. The maximum
number of hops in a RIP network is 15 as the protocol treats anything equal to
or greater than 16 as unreachable.
RIP 2
RIP version 2 adds capabilities to RIP. Some of the most notable RIP 2
enhancements follow.
Network Mask
RIP 1assumes that all subnetworks of a given network have the same network
mask. It uses this assumption to calculate the network masks for all routes
received. This assumption prevents subnets with different network masks
from being included in RIP packets. RIP 2 adds the ability to explicitly
specify the network mask for each network in a packet.
Authentication
RIP 2 packets also may contain one of two types of authentication methods
that may be used to verify the validity of the supplied routing data.
The first method is a simple password in which an authentication key of up to
16 characters is included in the packet. If this does not match what is
expected, the packet is discarded. This method provides very little security, as
it is possible to learn the authentication key by watching RIP packets.