• Using Switches to Create VLANs
• Network Attached Storage
• Storage Area Networks
• Disaster Recovery
• Fault Tolerance
• Working with a Small Network—The
• Security Impact on the Network
Using Switches to Create VLANs
• A local area network (LAN) is often
considered a broadcast domain
• Broadcast domains are bounded by any
device that translates above the physical
• VLANs are created using switches
• You can create a VLAN in three ways
• Early on, VLANs were constructed through the simple
assignment of ports on a switch to a VLAN identified by a
– Layer 2 grouping.
• The layer 2 grouping method is also called the MAC
Membership VLAN. As you might guess, it’s based on the
MAC address of the computer
– Layer 3 grouping.
• This method uses the network layer address to identify the
computers that should participate in a particular VLAN. If
TCP/IP is in use, this would be the IP address; if IPX/SPX is
in use, it would be the IPX address..
Network Attached Storage
• A NAS device is dedicated to nothing more than serving
the network with storage
• A NAS device is a server of sorts because it provides file
• A workstation in a network using NAS does not
authenticate to the NAS device
• NAS communicates using common
protocols, including :
– Network File System (NFS) typically found in
– Common Internet File System (CIFS) in
– File Transfer Protocol (FTP) and Hypertext
Transfer Protocol (HTTP) in IP networks
Storage Area Networks
• A SAN is a network of one or more storage devices that
communicate outside the regular network with one or more servers
• In the SAN, storage devices are placed on a separate network using
fibre channel technology to connect to a hub
• Servers are also equipped with special adapters to connect to the
hub and access the stored data on any of the connected storage
• SANs make it possible to separate large transfers of data from the
• Central management of data is possible via a SAN, yet the data is
still available to many different systems and applications
• Types of disasters you might encounter :
– Mission-critical server failures.
• Any component within a server can cause it to fail to provide
services, including hard disk, power supply, processor, memory, and
even the network interface.
– Network component failures.
• When network components such as hubs, switches, and routers fail,
entire sections of the network become unusable.
– Building problems.
• If the building power goes out, the wiring is damaged, or the wide
area network (WAN) link is cut, the network fails.
– Mother Nature.
• Floods, tornadoes, fires, and the occasional monsoon are the types
of disasters that can completely devastate the entire network and all
the data stored within it.
• In the event of a total disaster, these are your options :
– Wait to resume operations after a new site can be constructed.
– Temporarily move operations to another site in a different
– Use a “cold” site, which is another location with equipment
available to begin operations as soon as you can move
personnel to that location and restore data to that equipment.
– Use a “hot” site, which is another location that mirrors your
location’s data operations, usually is directly connected to your
network, and is able to begin operations the moment your
location is affected by the disaster.
• Fault tolerance is another term for redundancy
• less expensive to prevent a disaster than to restore one
• Fault tolerance can work for the following :
• Some servers support error-correcting memory
with a spare memory module to use in case of
– Network interface cards (NICs).
• NICs can be redundant in two ways. They can
share the network traffic, or one of the NICs can
wait until the first fails before it kicks in.
– Redundant Array of Inexpensive Disks (RAID).
• Data is mirrored, shared, or striped across multiple disks.
Pay attention to these versions of RAID:
• RAID 1: Mirroring disks connected to a single hard disk
controller, or duplexing disks connected to two different hard
• RAID 5: A group of three or more disks is combined into a
volume with the disk striped across the disks, and parity is
used to ensure that if any one of the disks fails, the
remaining disks will still have all data available.
– Power supplies.
• One power supply takes over if the original fails.
• Two or more servers are grouped to provide services as if
the group were a single server. A cluster is transparent to
end users. Usually, a server member of a cluster can take
over for a failed partner with no impact on the network.
Working with a Small Network
• The goals of a SOHO network are different from those of
an enterprise network. Most, listed below, are fairly
– Share an Internet connection.
– Share printers and scanners.
– Share files, access e-mail messages, and back up the
– Access a corporate network via virtual private network
– Send or receive faxes without a fax machine.
Using DSL to Access the Internet
• DSL uses standard telephone wires to carry high-speed data
• doesn’t interrupt standard telephone calls
• ADSL is ideal for SOHO networks
Using Cable Modems for Internet
• The Data Over Cable Service Interface Specification (DOCSIS) is
the cable TV industry’s response to the telephone companies’
domination over Internet connectivity
• Cable TV companies have since upgraded their backend networks
with hybrid fiber coax (HFC) to bring fiber optics into the cable TV
network, which does the trick
• In DOCSIS 1, a download bandwidth of 40 Mbps is available, with a
10-Mbps upload speed
• The media is shared by all the cable subscribers within a local area
• A cable modem is shared in the same way that a DSL connection
can be shared
• Direct broadcast satellite TV is another medium under exploration
for delivering high-speed Internet services
• The other type of home satellite is a point-to-point wireless service
using line of sight connections between the Internet Service
Provider (ISP) and the subscriber
• Dialup connections are the mainstay for many a SOHO
• SOHO will access the Internet only through individual
dialup connections on each of the network’s PCs
• However, it is possible to share a dialup connection