4 Determining IP Addresses
4-10
CJ-series EtherNet/IP Units Operation Manual for NJ-series CPU Unit (W495)
4-3 Private and Global Addresses
There are two kinds of IP addresses, private and global.
Generally, as shown below, global addresses in the intranet are allocated only to IP routers (such as
broadband routers) interfaced with the Internet. All other nodes in the intranet, which includes the Eth-
erNet/IP Unit, are allocated private addresses.
4-3-1 Private and Global Addresses
IP address Description
Global address These are IP addresses that connect directly to the Internet.
Allocated by application to NIC, each address is unique in
the world, and as many as 4.3 billion can be allocated world-
wide.
Private address These are IP addresses for Intranet (LAN) use. Direct con-
nection to the Internet is not possible. Frames that include
private IP addresses are restricted by the router from being
sent outside the LAN.
● Intranet
Personal computer
(e.g., Sysmac Studio)
Ethernet (EtherNet/IP)
Ethernet (EtherNet/IP)
Firewall
● Internet
● Intranet
Firewall
Controller
Controller
Controller
Private address
Personal computer
(e.g., Sysmac Studio)
Private address
Private address
Private address
Global address
IP router
Cannot connect to Internet
Cannot connect to Internet
Global address
Private address
Private address
IP router
(required)
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