User guide

E
XTREME
W
ARE
S
OFTWARE
U
SER
G
UIDE
12-3
O
VER VIEW OF
RIP
RIP has a number of limitations that can cause problems in large networks, including
the following:
• A limit of 15 hops between the source and destination networks
• A large amount of bandwidth taken up by periodic broadcasts of the entire routing
table
• Slow convergence
• Routing decisions based on hop count; no concept of link costs or delay
• Flat networks; no concept of areas or boundaries
OSPF offers many advantages over RIP, including the following:
• No limitation on hop count
• Route updates multicast only when changes occur
• Faster convergence
• Support for load balancing to multiple routers based on the actual cost of the link
• Support for hierarchical topologies where the network is divided into areas
The details of RIP and OSPF are explained later in this chapter.
O
VERVIEW OF
RIP
RIP is an Interior Gateway Protocol (IGP) first used in computer routing in the
Advanced Research Projects Agency Network (ARPAnet) as early as 1969. It is primarily
intended for use in homogeneous networks of moderate size.
To determine the best path to a distant network, a router using RIP always selects the
path that has the least number of hops. Each router that data must traverse is
considered to be one hop.
R
OUTING
T
ABLE
The routing table in a router using RIP contains an entry for every known destination
network. Each routing table entry contains the following information:
• IP address of the destination network
• Metric (hop count) to the destination network