Daisy-Chaining Devicemaster 4/8/16-Port Units - Comtrol DeviceMaster DM-2000 Series Installation And Configuration Manual

Troubleshooting and Technical Support

Daisy-Chaining DeviceMaster 4/8/16-Port Units

The DeviceMaster 4/8/16-port (panel mount) models with external power supplies follow the IEEE
specifications for standard Ethernet 10/100BASE-TX topologies.
Note: If the serial number of your product is above xxxx-030000, the UP and DOWN Ethernet ports are
interchangeable.
When using the UP and DOWN ports, the DeviceMaster 4/8/16 is classified as a switch. When using the UP
port only, it is a simple end node device.
The maximum number of daisy-chained DeviceMaster 4/8/16 units, and the maximum distance between units
is based on the Ethernet standards and will be determined by your own environment and the conformity of
your network to these standards.
Comtrol has tested with seven DeviceMaster 4/8/16 units daisy-chained together using 10 foot CAT5 cables,
but this is not the theoretical limit. You may experience a performance hit on the devices at the end of the
chain, so it is recommended that you overload and test for performance in your environment. The OS and the
application may also limit the total number of ports that may be installed.
Following are some quick guidelines and URLs of additional information. Note that standards and URLs do
occasionally change.
• Ethernet 10BASE-T Rules
- The maximum number of repeater hops is four.
- You can use Category 3 or 5 twisted-pair 10BASE-T cables.
- The maximum length of each cable is 100m (328ft).
Note: Category 3 or 5 twisted pair cables look the same as telephone cables but they are not the same.
The network will not work if telephone cables are used to connect the equipment.
• Fast Ethernet 100BASE-TX rules
- The maximum number of repeater hops is two (for a Class II hub). A Class II hub can be connected
directly to one other Class II Fast Ethernet hub. A Class I hub cannot be connected directly to another
Fast Ethernet hub.
- You must use Category 5 twisted-pair 100BASE-TX cables.
- The maximum length of each twisted-pair cable is 100m (328ft).
- The total length of twisted-pair cabling (across directly connected hubs) must not exceed 205m (672ft).
Note: Category 5 twisted pair cables look the same as telephone cables but they are not the same. The
network will not work if telephone cables are used to connect the equipment.
• IEEE 802.3 specification: A network using repeaters between communicating stations (PCs) is subject to
the 5-4-3 rule of repeater placement on the network:
- Five segments connected on the network.
- Four repeaters.
- Three segments of the 5 segments can have stations connected. The other two segments must be inter-
repeater link segments with no stations connected.
Additional information may be found by searching the web.
166 - Troubleshooting and Technical Support DeviceMaster Installation and Configuration Guide: 2000594 Rev. F