1 Learning objectives

To get basic skills in business(office) network access settings

On the base of the D-Link router (DI 524).

2 Key positions

LANs perform two main networking functions: a)

local high-speed data exchange within the network at a speed about 10-100

Mbps and above; b) external data exchange; as a rule it is access to the Internet at

relatively low speed about 64-2048 Kbps and above. In addition

nowadays it happens to be a benefit to use combined technology

in local network access - wired and wireless. To build

networks of this type multifunction network device are used; they can

have different names (routers, switches, access points, etc.)

but names do not always adequately reflect functional properties

of the equipment. Example of a relatively inexpensive devices of this type are

D-Link company routers with wired and wireless

access. These devices should be used in small office and

home network with the total number of computers about 2-16.

In this laboratory work DI 524 access point is used ,it’s the representative of D-Link family . You can use it to organize two segments of a LAN

Ethernet with common MAC address spaces-layer. Speed

of internal exchange is up to 100 Mbps in the wire segment and up to 54 Mbit/s

(really noticeably smaller) in wireless. Range of coverage is determined by the

maximum cable length and radius of the radio channel in the premises (both

within 100 m). External exchange bitrate depends on the capabilities of the external network (this may be the fast exchanges with external local network hosts and more slow exchange from remote hosts on the Internet).

 

 

2. 1 Description of the laboratory bench

Laboratory benchas as a layout network segment of WiFi access is a set of hardware and software modules that implement the following network

function:

-proxy server with port and address translation (NAT/PAT);

-DHCP –server of dynamic host configuration;

-gateway router for connect of the internal LAN with external network WAN;

-network screen filter for easy access control functions realization into the external network (IP and MAC addresses, and name resolution

domains);

-Firewall -screen filter for complex controls access configuration to the external network;

-function "demilitarized zone" (DMZ);

- function of destination server dynamic DNS(dynamic server) (DDNS);

-module of access points configuration.

All these functions are implemented by basic device DI-524 which is conditionally

called "router or WiFi access point”. This device has two logical interfaces:

a) internal: MAC address = 00 15-E9-E2-5F-93 (fixed);

b) external: MAC address = 00 15-E9-E2-5F-92 (customizable);

The default (or after a reset with button Reset) factory

installation operate: internal interface IP address is 192.168.0.1 net mask is

255.255.255.0 (or/24 in short). This means that the address of the internal

network by default is 192.168.0/24 (Classless network numbering system

CIDR). External MAC address which is set by default can be changed using

DI-524 router settings. The necessity of this need arises when external ISP-provider tightly controlls host access to its network with help of associating them to a fixed physical address of specific apparatus interface for each host. In this case the router "supplies" in the network instead of host, MAC address of the router is replaced by the the MAC address of the host. Because the interfaces and the external interface of the host router are in different LANs (separated by the gateway router)then the existence of two identical MAC address does not

conflict.

The IP address on the external interface is typically configured automatically (i.e.,

assigned by the DHCP-server is the upstream network (in this case it is a local

Networking of Academy).

Module of access point configuration has a fixed IP address

192.168.0.1 with mask 24, and access is possible only at the condition that

Access Terminal (i.e. LAN host) is located in the same network

192.168.0/24. In turn, the local network address can be set by

any manual configuration other than the initial factory default configuration. It is important to have in mind when configuring a custom router.

Feature of internal interface is that the on MAC levels there is only one

IP while the bottom layer and physical layer it is devided into two

branches:

-wired interface standard 10/100 Base-T;

-wireless IEEE 802.11 g.

The first branch is Fast Ethernet 100 Mbit/s on two twisted copper pair (with

automatic switching on the bitrate 10 Mbit/s if

100 Mbit/s bitrate is impossible). This branch has four ports (connectors RJ-45).

The second branch is a radio-Ethernet of WiFi standard; number of the connection points is not required by the technical parameters of router.

But their numbers are actually limited demand acceptable speed

access to the external network (usually Internet Channel access). Thus in the

passport exchange bitrate through internal radio network IEEE 802.11 g standard on 54 Mgbit/s ,real access bitrate even when one subscriber is about 20-

30 Mbit/s. When you increase the number of subscribers average access bitrate drops faster then growth of the subscribers number due to the collisions of access to a common radio channel which in this case is the analogous to the “shared bus cable”.

Because external channel of 64 Kbps feelingof "braking" in the network will not be visible for 3-5 parallely working sunscribers. Maximum

number of subscribers in practice is within 8-10.

External interface (WAN) is of type E 10/100 Base-T. In our case for

the Internet access this interface is typically switched in a local network

of Academy (192.168.1/24).

 

 

Terminal of router configuration is LAN host

( preferably connected to a wired interface ) configured on the network

192.168.0/24. Access to the module configuration is done via the Web

browser (MS Internet Explorer, Mozilla FireFox, etc.) showing the address access

http://192.168.0.1 . Similar access via radio channel can be fragile (after the first occurrence in Setup mode, reentry blocked ).

Router does not have its own DNS server function but it supports dynamic redirection to an external DNS server which is manually configured in settings (this feature is implemented by the DDNS).

Function " proxy "implements the direct conversion of any pair

“the internal IP address + internal port” into a pair “ common external IP address + free external port” is in the process of packets forwarding from a local network in external WAN and reverse translation – when you receive responses from the outside and transfer their internal hosts. The internal hosts are not visible from outside. However there are situations where you must select one of the hosts

as a publicly accessible from both inside and outside of the object (lets say Web

server). In this case DMZ function is used; host with the specified address

is placed in the so-called neutral zone and is visible on both sides of the access point . This is easily verified pingovaniem host outside and inside.