User guide

12-2 E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
I
NTERIOR
G
ATEWAY
R
OUTING
P
ROTOCOLS
• Interconnections: Bridges and Routers
by Radia Perlman
ISBN 0-201-56332-0
Published by Addison-Wesley Publishing Company
O
VERVIEW
The switch supports the use of two interior gateway protocols (IGPs); the Routing
Information Protocol (RIP) and the Open Shortest Path First (OSPF) protocol for IP
unicast routing.
RIP is a distance-vector protocol, based on the Bellman-Ford (or distance-vector)
algorithm. The distance-vector algorithm has been in use for many years, and is widely
deployed and understood.
OSPF is a link-state protocol, based on the Dijkstra link-state algorithm. OSPF is a
newer Interior Gateway Protocol (IGP), and solves a number of problems associated
with using RIP on today’s complex networks.
Both RIP and OSPF can be enabled on a single VLAN.
RIP V
ERSUS
OSPF
The distinction between RIP and OSPF lies in the fundamental differences between
distance-vector protocols and link-state protocols. Using a distance-vector protocol, each
router creates a unique routing table from summarized information obtained from
neighboring routers. Using a link-state protocol, every router maintains an identical
routing table created from information obtained from all routers in the autonomous
system. Each router builds a shortest path tree, using itself as the root. The link-state
protocol ensures that updates sent to neighboring routers are acknowledged by the
neighbors, verifying that all routers have a consistent network map.
The biggest advantage of using RIP is that it is relatively simple to understand and
implement, and it has been the de facto routing standard for many years.