Allied Telesis AT-8100 Series - Manual (Page 1852)

Chapter 106: Routing Information Protocol (RIP)
1852
Overview
The AT-8100 Series switches provide Layer 3 routing functionality as well
as Layer 2 switching functionality. When Virtual LANs (VLANs) are
applied, the end nodes who belong to different VLANs cannot
communicate, even though they are physically connected through a
switch or switches. With Layer 3 routing functionality, the Layer 3 switches
can make end nodes on different VLANs communicate without a router.
The AT-8100 Series switches also support Routing Information Protocol
(RIP) to communicate with other Layer 3 switches or routers so that the
switches can communicate with remote networks.
A routing protocol specifies how routing devices, such as a router or Layer
3 switch, send routing information to other routers. With a routing protocol,
routing devices can learn about remote networks and add the information
to their routing tables dynamically. Based on the routing tables, routing
devices forward packets to other networks. A routing protocol uses a
metric to determine which path to send a packet to a given destination
across the network.
Routing Information Protocol (RIP) is a distance-vector routing protocol,
which uses hop counts as its metric. RIP determines a best route to a
remote destination based on the hop count, the number of routers which
the packet traverses. Each hop in a path from source to destination is
assigned a hop count value. For instance, a device that is directly
connected to the switch has a hop count of zero. The maximum number of
hops allowed for RIP is 15. Due to the small range of the metric, RIP is
suitable for smaller networks.
By default, RIP prevents routing loops with a feature called split horizon
with poison reverse. With this feature, the hop count is assigned to 16
which is equal to infinity.
RIP sends routing update messages at regular, 30 second, intervals when
the network topology changes. This process is called advertising. When
receiving a routing update message (including a change), a routing device
updates its routing table to reflect the change.
The AlliedWare Plus™ Management Software supports both RIP Version
1 and 2. With the implement of RIP Version 2, the Management Software
supports authentication and allows you to enable and disable automatic
route summarization. For more information about authentication and
automatic summarization, see “Enabling Authentication” on page 1856”
and “Enabling and Disabling Automatic Route Summarization” on
page 1858.