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Private and Global Addresses Section 5-3
5-3 Private and Global Addresses
5-3-1 Private and Global Addresses
There are two kinds of IP addresses, private and global.
• Global addresses: 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 million can be allocated worldwide.
• Private addresses: These are IP addresses for Intranet (LAN) use, and
cannot connect directly to the Internet. Frames that
include private IP addresses are restricted by the
router from being sent outside the LAN.
Generally, as shown below, global addresses in the intranet are allocated only
to IP routers (such as broadband routers) interfacing with the Internet. All
other nodes in the intranet, including the EtherNet/IP Unit or built-in EtherNet/
IP port, are allocated private addresses.
Communications Services
That Require Global
Addresses for EtherNet/IP
Units and built-in
EtherNet/IP ports
A global address is required for the IP addresses of the EtherNet/IP Units and
built-in EtherNet/IP port when the following communications services are
used over the Internet.
• FINS communications services
• Explicit message communications services
Intranet
Personal computer,
CX-Programmer, etc.
Ethernet (EtherNet/IP)
PLC
Firewall
IP router
Private address
Internet
Global address
(required)
Intranet
Private address
IP router
Global address
Private address
Firewall
Ethernet (EtherNet/IP)
PLC PLC
Private address Private address
Not output to Internet
Personal computer,
CX-Programmer, etc.
Not output to Internet
Private address