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Cisco 860 Series, Cisco 880 Series, and Cisco 890 Series Integrated Services Routers Software Configuration Guide
OL-18906-02
Appendix B Concepts
Routing Protocol Options
IP is a connectionless protocol, which means that IP does not exchange control information (called a
handshake) to establish an end-to-end connection before transmitting data. In contrast, a
connection-oriented protocol exchanges control information with the remote computer to verify that it
is ready to receive data before sending it. When the handshaking is successful, the computers have
established a connection. IP relies on protocols in other layers to establish the connection if
connection-oriented services are required.
Internet Packet Exchange (IPX) exchanges routing information using Routing Information Protocol
(RIP), a dynamic distance-vector routing protocol. RIP is described in more detail in the following
sections.
Routing Protocol Options
Routing protocols include the following:
• Routing Information Protocol (RIP)
• Enhanced Interior Gateway Routing Protocol (Enhanced IGRP)
RIP and Enhanced IGRP differ in several ways, as shown in Table B-1.
RIP
RIP is an associated protocol for IP and is widely used for routing protocol traffic over the Internet. RIP
is a distance-vector routing protocol, which means that it uses distance (hop count) as its metric for route
selection. Hop count is the number of routers that a packet must traverse to reach its destination. For
example, if a particular route has a hop count of 2, then a packet must traverse two routers to reach its
destination.
By default, RIP routing updates are broadcast every 30 seconds. You can reconfigure the interval at
which the routing updates are broadcast. You can also configure triggered extensions to RIP so that
routing updates are sent only when the routing database is updated. For more information on triggered
extensions to RIP, see the
Cisco IOS Release 12.3 documentation set.
Ta b l e B-1 RIP and Enhanced IGRP Comparison
Protocol Ideal Topology Metric Routing Updates
RIP Suited for topologies with
15 or fewer hops.
Hop count. Maximum hop
count is 15. Best route is one
with lowest hop count.
By default, every 30 seconds.
You can reconfigure this value
and also use triggered
extensions to RIP.
Enhanced
IGRP
Suited for large topologies
with 16 or more hops to
reach a destination.
Distance information. Based
on a successor, which is a
neighboring router that has a
least-cost path to a
destination that is
guaranteed to not be part of
a routing loop.
Hello packets sent every
5
seconds, as well as
incremental updates sent
when
the state of a destination
changes.