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HELIX DN9848E Remote Control Software
User Guide
87
IP Addressing
To uniquely identify every device, Ethernet connections use standard IP addresses comprising four
0-255 segments presented in dot notation, for example, 192.168.1.16. To accommodate widely varying
sizes of system, including those with sub-systems, the segments can be used in slightly differing ways.
The format used by a particular IP address is defined by its ‘subnet mask’, as follows:
a) On a small ‘Class C’ system (less than 256 devices), the subnet mask is 255.255.255.0 indicating
that the first three segments identify the system and are shared by all of the equipment on the
system, while the last segment uniquely identifies each device, for example, in 192.168.1.16, the
system subnet is 192.168.1 and the Device ID is 16. Typically, this is the subnet mask used for
IP addresses on a HELIX DN9848E RCS system.
b) For larger systems, the first one or two segments identify the system and the remaining
segments identify the sub-system, if relevant, and individual equipment. For example, a Class B
medium sized system uses a 255.255.0.0 subnet mask, indicating the first two segments identify
the system and the last two the sub-system and individual device.
Wireless Routing
For wireless connection, the laptop/PC wireless card and Access Point must be set up to locate and
recognise each other, noting that the airwaves are shared with other devices. This is done by initially
making a wired connection from the laptop/PC to the Access Point to assign the appropriate identifiers
etc. After configuration, the wired connection can be removed and the wireless one made. There is no
need to repeat the wired connection step on future set ups, provided no part of the wireless system has
changed.
Two identifiers are used in the recognition process, as follows:
Service Set Identifier (SSID) – The Access Point broadcasts this to enable nearby devices to
locate it. Broadcast may be disabled, so that the Access Point only flags its presence when
another device calls it by name, that is, its SSID. This mode should be used for the HELIX
DN9848E RCS wireless connection to provide security against unauthorised users accessing the
system.
Authentication code – This ensures that the device trying to connect to the Access Point has the
right to access the system, thus providing an extra layer of security against unauthorised users.
Although there are various authentication methods*, the worked example in the next section
specifically covers the basic Wireless Equivalent Privacy (WEP) key scheme, which uses a long
sequence of numbers as the key. If you wish to use a more complex scheme, please consult the
Access Point and wireless Ethernet card manuals.
* WPA-PSK (Wi-Fi Protected Access – Pre-Shared Key) is now available on Access Point and some wireless cards.
In addition, the broadcast channel of the Access Point can be specified (typically channels 1 to 11 are
available); this is particularly useful if there are other Access Points in the vicinity.
Note Every Ethernet connection on your Laptop/PC has a different IP address. Therefore, when you
have both wired and wireless Ethernet cards on your laptop/PC, be sure to enter the correct
settings for each.