Networking Basics; Ip Addressing; About The Subnetwork Mask - Acuity Controls nLight ECLYPSE User Manual

IPv4 Communication Fundamentals

Networking Basics

When manually configuring the TCP/IP interface on an ECLYPSE IP controller (the DHCP option is not used), an IP ad-
dress, subnetwork mask, and a default gateway are required in the Network Settings.

IP Addressing

The most widely used internet addressing scheme is IPv4. It codes an IP address in 32 bits.
An IPv4 address is made up of two parts defined by a subnetwork mask; the network portion (which identifies a specific
network or subnetwork) and the host portion (which identifies a specific device).

About the Subnetwork Mask

Devices on the same sub-network can address IP packets to each other directly without routing. The range of IP ad-
dresses available in a sub-network is defined by the subnetwork mask. This is also called the subnetwork mask's 'address
space'. The subnetwork mask is coded in 32 bits as follows.
An IP packet addressed to a device on another network portion will have to be routed through the router's WAN port as
such an address is not local. BACnet/IP broadcast discovery messages such as "Who-Is" do not pass through network
routers that separate subnetworks. This means that BACnet/IP controllers on different subnetworks will not normally com-
municate with each other.
BBMD allows broadcast message to pass through a router: on each subnet, a single device has BBMD enabled. Each
BBMD device ensures BACnet/IP connectivity between subnets by forwarding broadcast messages found on its subnet-
work to each other, and then onto the local subnetwork as a broadcast message. See BBMD Settings.
Network Class CIDR
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nLight ECLYPSE
Subnetwork Mask Block
Size
255.0.0.0 256
255.128.0.0 128
255.192.0.0 64
255.224.0.0 32
255.240.0.0 16
255.248.0.0 8
255.252.0.0 4
255.254.0.0 2
255.255.0.0 256
255.255.128.0 128
255.255.192.0 64
255.255.224.0 32
255.255.240.0 16
255.255.248.0 8
255.255.252.0 4
255.255.254.0 2
255.255.255.0 256
255.255.255.128 128
255.255.255.192 64
255.255.255.224 32
255.255.255.240 16
255.255.255.248 8
255.255.255.252 4
Number of Subnetworks
according to the Network Type
Class A Class B Class C
1
2
4
8
16
32
64
128
256 1
512 2
1024 4
2048 8
4096 16
8192 32
16384 64
32768 128
65536 256
131072 512
262144 1024
524288 2048
1048576 4096
2097152 8192
4194304 16384
Number of Hosts
according to the Network Type
Class A Class B
16777214
8388606
4194302
2097150
1048574
525286
262142
131070
65534 65534
32766 32766
16382 16382
8190 8190
4094 4094
2046 2046
1022 1022
510 510
1 254 254
2 126 126
4 62 62
8 30 30
16 14 14
32 6 6
64 2 2
Class C
254
126
62
30
14
6
2
14