2.6 Describe common elements of networking
Subnetting : It is nothing but creating
networks within a network. Subnetting allows an organization
with a single IP address (Class A /ClassB /ClassC) to have multiple
subnetworks, thus allowing several physical networks within
Default subnet mask for Class A network: 255.0.0.0
Default subnet mask for Class B network: 255.255.0.0
Default subnet mask for Class C network: 255.255.255.0
The directed broadcast should reach all Hosts on the intended
network (or subnet, if sub netted). For example, the directed
broadcast address for an IP network 220.127.116.11 with default
subnet mask is 18.104.22.168. This is arrived by putting all
1s for the host portion of the IP address.
DNS (Domain Name Service) : is used for
resolution of domain names to IP addresses. WINS, LMHOSTS is
used for resolution of NetBIOS names to IP addresses.
DHCP : Dynamic Host Computer Protocol, which
leases IP addresses and other parameters like subnet mask, default
gateway to client computers dynamically. You have to assign
the IP address for your DHCP server statically. A DHCP server
can't assign an IP address to itself. Similarly, some other
Servers which need static assignment of IP addresses are your
DNS server, WINS server, Default gateway.
Static Addressing : You can request a static
IP address it is one IP address for only one customer and is
constant. These are more reliable for VOIP, for hosting gaming
websites and to use VPN. Another advantage is that because you
IP is static that is it will not be assigned to any other you
need not worry of your IP getting blacklisted because of some
only else sending SPAM.
Dynamic addressing : When DHCP client boots,
it sends out a DHCP discover message. All DHCP servers answer
with an offer message that includes an address which is available
to the client. client machine typically repeats the discover
message several times to make sure it hears from all the servers,
then eventually chooses one server The currently active DHCP
server is configured by hand to handle and reserve IP addresses
and the IP configuration information that goes with them. Addresses
are made available in an order that permits a client to have
the best chance of getting back the same address it was using
most recently. IP configuration information gets automatically
configured for your client machine by the DHCP server.
VPN : VPN stands for Virtual Private Network.
A VPN provides a mechanism to access corporate networks safely
using Internet. VPN uses encryption to ensure only authorized
user can access the corporate resources. A secure tunnel is
created through the public network through which the packets
are transported between the remote computer and the corporate
network. Vit is used for accessing a corporate network securely
from remote locations using public Internet. There are two widely
known protocols that can be implemented for enabling VPN communications:
1. PPTP: PPTP stands for Point to Point Tunneling Protocol.
It is a PPTP is pioneered by Microsoft and others is a widely
2. L2TP: L2TP stands for Layer Two (2) Tunneling Protocol.
L2TP merges the best features of PPTP and L2F (from Cisco
PPTP and L2TP protocols together with PPP protocol enable
ISPs to operate Virtual Private Networks (VPNs).
VLAN – Virtual Local Area Networks:
VLAN derives it's name from the fact that there is only
one physical network, but two or more logical networks.
A VLAN may be created by any of these methods:
VLAN by port association - Membership in a VLAN can be
defined based on the ports that belong to the VLAN. For
example, in a bridge with four ports, ports 1, 2, and 4
belong to VLAN 1 and port 3 belongs to VLAN 2. The main
disadvantage of this method is that it does not allow for
user mobility. If a user moves to a different location away
from the assigned bridge, the network manager must reconfigure
VLAN by MAC address association: Here, membership in
a VLAN is based on the MAC address of the workstation. The
switch tracks the MAC addresses which belong to each VLAN
(see Figure4). Since MAC addresses form a part of the workstation's
network interface card, when a workstation is moved, no
reconfiguration is needed to allow the workstation to remain
in the same VLAN. This is unlike Layer 1 VLAN's where membership
tables must be reconfigured. The main problem with this
method is that VLAN membership must be assigned initially.
In networks with thousands of users, this is no easy task.
Also, in environments where notebook PC's are used, the
MAC address is associated with the docking station and not
with the notebook PC. Consequently, when a notebook PC is
moved to a different docking station, its VLAN membership
must be reconfigured.
VLANs by Protocol Type - VLAN membership for Layer 2
VLAN's can also be based on the protocol type field found
in the Layer 2 header. For example, VLANs that carry only
IP traffic and those that carry only IPX traffic. However
this type of VLANs are not popular.
VLANs by IP subnet address - Membership is based on the
Layer 3 header. The network IP subnet address can be used
to classify VLAN membership. Although VLAN membership is
based on Layer 3 information, this has nothing to do with
network routing and should not be confused with router functions.
In this method, IP addresses are used only as a mapping
to determine membership in VLAN's. No other processing of
IP addresses is done. In Layer 3 VLAN's, users can move
their workstations without reconfiguring their network addresses.
The only problem is that it generally takes longer to forward
packets using Layer 3 information than using MAC addresses.
This is the most widely used VLAN type.
DMZ (DeMilitalized Zone) : It is a place
separate from the LAN where servers reside that can be reached
by users on the Internet. If a company intends to host its own
servers to be accessed from public Internet, a DMZ is most preferred
solution. The network segment within the DMZ is secured by two
firewalls, one interfacing with the public Internet, and the
other interfacing the internal corporate network. Thus, a DMZ
provides additional layer of security to internal corporate
network. The type of servers that are hosted on DMZ may include
web servers, email servers, file servers, DNS servers, etc.
Ethernet Types :
CAT3: This standard was used in 90's for homes and offices.
It can transmit data up to 10Mbps with a possible bandwidth
CAT5: It uses either the 10BASE-T or 100BASE-T standard
for data transmission Using two cable pairs to signal over
copper wire. It provides a minimum of 100MHz of bandwidth.
CAT5e: It uses four pairs of copper wire. In addition,
the wire pairs are twisted more tightly and are sheathed
in heavy-duty shielding to eliminate crosstalk. It is used
for 1000BASE-T networks, which carry data at a rate of 1
CAT6: It can transmit data up to 10Gbps, has a minimum
of 250MHz of bandwidth and specifies cable lengths up to
100 meters with 10/100/1000Mbps transfer, along with 10Gbps
over shorter distances. It is made up of four twisted pairs
of copper wire, an longitudinal separator separates each
of the four pairs of wires from each other
CAT 6a: It can operate at a frequency of up to 750 MHz
and is even less susceptible to interference and crosstalk
CAT6a is the preferred cable for 10GBASE-T Ethernet