Rip; Enhanced Igrp; Ppp Authentication Protocols - Cisco CISCO851-K9 - 851 Integrated Services Router Configuration Manual

Appendix B Concepts
RIP and Enhanced IGRP differ in several ways, as shown in
Table B-1
Protocol

RIP

Enhanced
IGRP
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.

Enhanced IGRP

Enhanced IGRP is an advanced Cisco proprietary distance-vector and link state routing protocol, which
means it uses a metric more sophisticated than distance (hop count) for route selection. Enhanced IGRP
uses a metric based on a successor, which is a neighboring router that has a least-cost path to a
destination that is guaranteed not to be part of a routing loop. If a successor for a particular destination
does not exist but neighbors advertise the destination, the router must recompute a route.
Each router running Enhanced IGRP sends hello packets every 5 seconds to inform neighboring routers
that it is functioning. If a particular router does not send a hello packet within a prescribed period,
Enhanced IGRP assumes that the state of a destination has changed and sends an incremental update.
Because Enhanced IGRP supports IP, you can use one routing protocol for multiprotocol network
environments, minimizing the size of the routing tables and the amount of routing information.

PPP Authentication Protocols

The Point-to-Point Protocol (PPP) encapsulates network layer protocol information over
point-to-point links.
OL-5332-01
RIP and Enhanced IGRP Comparison
Ideal Topology
Suited for topologies with
15 or fewer hops.
Suited for large topologies
with 16 or more hops to
reach a destination.
Cisco 850 Series and Cisco 870 Series Access Routers Software Configuration Guide
Table B-1.
Metric
Hop count. Maximum hop
count is 15. Best route is one
with lowest hop count.
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.
PPP Authentication Protocols
Routing Updates
By default, every 30 seconds.
You can reconfigure this value
and also use triggered
extensions to RIP.
Hello packets sent every
5 seconds, as well as
incremental updates sent
when the state of a destination
changes.
B-3