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A network administrator must
anticipate and manage the physical growth of a network, perhaps by
buying or leasing another floor of the building to house new
networking equipment such as racks, patch panels, switches, and
routers. The network designer must choose an addressing scheme
that allows for growth. Variable-Length Subnet Masking (VLSM) is a
technique that allows for the creation of efficient, scalable
addressing schemes.
With the phenomenal growth of the Internet and TCP/IP, virtually
every enterprise must now implement an IP addressing scheme. Many organizations
select TCP/IP as the only routed
protocol to run on their network. Unfortunately, the architects of TCP/IP
could not have predicted that their protocol would eventually
sustain a global network of information, commerce, and
entertainment.
Twenty years ago, IP version 4 (IPv4)
offered an addressing strategy that, although scalable for a time,
resulted in an inefficient allocation of addresses. IP version 6 (IPv6),
with virtually unlimited address space, is slowly being implemented in
select networks and may replace IPv4 as the dominant
protocol of the Internet. Over the past two decades, engineers have successfully
modified IPv4 so that it can survive the exponential
growth of the Internet. VLSM is one of the modifications that has helped to bridge the
gap between IPv4 and IPv6.
Networks must be scalable in order to
meet the changing needs of users. When a network is scalable it is able
to grow in a logical, efficient, and cost-effective way. The routing
protocol used in a network does much to determine the scalability of
the network. Therefore, it is important that the routing protocol be
chosen wisely. Routing Information Protocol (RIP) is still considered
suitable for small networks, but is not scalable to large networks
because of inherent limitations. To overcome these limitations yet
maintain the simplicity of RIP version 1 (RIP v1), RIP version 2 (RIP v2)
was developed.
Students completing this module should be
able to:
- Define VLSM and briefly describe the
reasons for its use
- Divide a major network into subnets of
different sizes using VLSM
- Define route aggregation and
summarization as they relate to VLSM
- Configure a router using VLSM
- Identify the key features of RIP v1 and
RIP v2
- Identify the important differences
between RIP v1 and RIP v2
- Configure RIP v2
- Verify and troubleshoot RIP v2
operation
- Configure default routes using the
ip route
and ip default-network
commands
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