endpoints on a point-to-point serial link. The
example for Singapore to Kuala Lumpur is configured as
follows: Singapore(config)#interface serial 0
Singapore(config-if)#ip address 192.168.10.137
255.255.255.252 KualaLumpur(config)#interface serial
1
KualaLumpur(config-if)#ip address 192.168.10.138
255.255.255.252
Content 1.2 RIP Version
2 1.2.1 RIP history The Internet is a
collection of autonomous systems (AS). Each AS is generally
administered by a single entity. Each AS will have its own
routing technology, which may differ from other autonomous
systems. The routing protocol used within an AS is referred to
as an Interior Gateway Protocol (IGP). A separate protocol,
called an Exterior Gateway Protocol (EGP), is used to transfer
routing information between autonomous systems. RIP was
designed to work as an IGP in a moderate-sized AS. It is not
intended for use in more complex environments. RIP v1 is
considered an interior gateway protocol that is classful. RIP
v1 is a distance vector protocol that broadcasts its entire
routing table to each neighbor router at predetermined
intervals. The default interval is 30 seconds. RIP uses hop
count as a metric, with 15 as the maximum number of hops. If
the router receives information about a network, and the
receiving interface belongs to the same network but is on a
different subnet, the router applies the one subnet mask that
is configured on the receiving interface: - For Class A
addresses, the default classful mask is 255.0.0.0.
- For
Class B addresses, the default classful mask is
255.255.0.0.
- For Class C addresses, the default
classful mask is 255.255.255.0.
RIP v1 is a popular
routing protocol because virtually all IP routers support it.
The popularity of RIP v1 is based on the simplicity and the
universal compatibility it demonstrates. RIP v1 is capable of
load balancing over as many as six equal-cost paths, with four
paths as the default. RIP v1 has the following limitations:
- It does not send subnet mask information in its
updates.
- It sends updates as broadcasts on
255.255.255.255.
- It does not support
authentication.
- It is not able to support VLSM or
classless interdomain routing (CIDR).
RIP v1 is
simple to configure, as shown in Figure .
Content
1.2 RIP Version 2 1.2.2 RIP v2
features RIP v2 is an improved version of RIP v1 and shares
the following features: - It is a distance vector
protocol that uses a hop count metric.
- It uses
holddown timers to prevent routing loops – default is 180
seconds.
- It uses split horizon to prevent routing
loops.
- It uses 16 hops as a metric for infinite
distance.
RIP v2 provides prefix routing, which
allows it to send out subnet mask information with the route
update. Therefore, RIP v2 supports the use of classless routing
in which different subnets within the same network can use
different subnet masks, as in VLSM. RIP v2 provides for
authentication in its updates. A set of keys can be used on an
interface as an authentication check. RIP v2 allows for a
choice of the type of authentication to be used in RIP v2
packets. The choice can be either clear text or Message-Digest
5 (MD5) encryption. Clear text is the default. MD5 can be used
to authenticate the source of a routing update. MD5 is
typically used to encrypt enable secret passwords and it has no
known reversal. RIP v2 multicasts routing updates using the
Class D address 224.0.0.9, which provides for better
efficiency.
Content 1.2 RIP Version 2
1.2.3 Comparing RIP v1 and v2 RIP uses distance
vector algorithms to determine the direction and distance to
any link in the internetwork. If there are multiple paths to a
destination, RIP selects the path with the least number of
hops. However, because hop count is the only routing metric
used by RIP, it does not necessarily select the fastest path to
a destination. RIP v1 allows routers to update their routing
tables at programmable intervals. The default interval is 30
seconds. The continual sending of routing updates by RIP v1
means that network traffic builds up quickly. To prevent a
packet from looping infinitely, RIP allows a maximum hop count
of 15. If the destination network is more than 15 routers away,
the network is considered unreachable and the packet is
dropped. This situation creates a scalability issue when
routing in large heterogeneous networks. RIP v1 uses split
horizon to prevent loops. This means that RIP v1 advertises
routes out an interface only if the routes were not learned
from updates entering that interface. It uses holddown timers
to prevent routing loops. Holddowns ignore any new information
about a subnet indicating a poorer metric for a time equal to
the holddown timer. Figure summarizes the behavior of RIP v1
when used by a router. RIP v2 is an improved version of RIP v1.
It has many of the same features of RIP v1. RIP v2 is also a
distance vector protocol that uses hop count, holddown timers,
and split horizon. Figure compares and contrasts RIP v1 and RIP
v2. Lab Activity Lab Exercise: Review of Basic Router
Configuration with RIP In this lab, the students will setup an
IP addressing scheme using Class B networks and configure
Routing Information Protocol (RIP) on routers. Lab
Activity e-Lab Activity: Review of Basic Router
Configuration including RIP In this lab, the students will
review the basic configuration of routers. Interactive
Media Activity Checkbox: RIP v1 and RIP v2 Comparison When
the student has completed this activity, the student will be
able to identify the difference between RIP v1 and RIP v2.
Content 1.2 RIP Version 2 1.2.4
Configuring RIP v2 RIP v2 is a dynamic routing protocol
that is configured by naming the routing protocol RIP Version
2, and then assigning IP network numbers without specifying
subnet values. This section describes the basic commands used
to configure RIP v2 on a Cisco router. To enable a dynamic
routing protocol, the following tasks must be completed:
- Select a routing protocol, such as RIP v2.
-
Assign the IP network numbers without specifying the subnet
values.
- Assign the network or subnet addresses and
the appropriate subnet mask to the interfaces.
RIP
v2 uses multicasts to communicate with other routers. The
routing metric helps the routers find the best path to each
network or subnet. The router command starts the routing
process. The network command causes the implementation
of the following three functions: - The routing updates
are multicast out an interface.
- The routing updates
are processed if they enter that same interface.
- The
subnet that is directly connected to that interface is
advertised.
The network command is required
because it allows the routing process to determine which
interfaces will participate in the sending and receiving of
routing updates. The network command starts up the
routing protocol on all interfaces that the router has in the
specified network. The network command also allows the
router to advertise that network. The router rip version
2 command specifies RIP v2 as the routing protocol, while
the network command identifies a participating attached
network. In this example, the configuration of Router A
includes the following: - router rip version 2 –
Selects RIP v2 as the routing protocol.
- network
172.16.0.0 – Specifies a directly connected network.
- network 10.0.0.0 – Specifies a directly connected
network.
The interfaces on Router A connected to
networks 172.16.0.0 and 10.0.0.0, or their subnets, will send
and receive RIP v2 updates. These routing updates allow the
router to learn the network topology. Routers B and C have
similar RIP configurations but with different network numbers
specified. Figure shows another example of a RIP v2