ADTRAN Atlas 550 - Manual (Page 115)

61200305L1-1 ATLAS 550 User Manual 9-1
Chapter 9
Router
OVERVIEW
The ATLAS 550 router provides remote connectivity of LANs within an
ATLAS 550—from LAN-to-WAN connection or from WAN-to-WAN
connection.
Internet Protocol (IP) routing is performed at layer 3 of the Open System In-
terconnection (OSI) model. (See Appendix B, OSI Model and Frame Relay
Technology Overview, for a discussion of the OSI model.) The routing process
determines the optimal path for data packets to travel and then moves the
data packets along that path. Routers exchange information about paths or
routes that reach additional LAN segments. This exchange of routing infor-
mation allows a router to build a detailed knowledge of the network topol-
ogy. Criteria for selecting the best path can include such items as distance,
number of hops (servers or routers), and cost of the transportation media.
The ATLAS 550 supports Routing Information Protocol (RIP), a protocol
based on hops. Each route has a set number of hops (routers or servers) that
it must travel through to reach a final destination. If a new route to a host
address that has a fewer number of hops is learned, it becomes the preferred
route. When a new route is learned, the router increments the hop count by
one and immediately broadcasts the new route over the other interfaces. To
prevent routing loops, RIP defines a hop count of 16 as an infinite or un-
reachable route.
The R OUTER M ENU defines, configures, and monitors all ATLAS 550 R OUTER
options. Figure 9-1 on page 9-2 displays the IP Router menu tree.