Private And Global Addresses - Omron CJ1W-EIP21 - 10-2010 Operation Manual

Private and Global Addresses

5-3

Private and Global Addresses

5-3-1 Private and Global Addresses
Intranet
Global address
IP router
Firewall
Communications Services
That Require Global
Addresses for EtherNet/IP
Units and built-in
EtherNet/IP ports
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There are two kinds of IP addresses, private and global.
• Global addresses: These are IP addresses that connect directly to the
• Private addresses: These are IP addresses for Intranet (LAN) use, and
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.
Intranet
Firewall
IP router
Internet
Private address
Ethernet (EtherNet/IP)
PLC
Private address
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
Internet. Allocated by application to NIC, each
address is unique in the world, and as many as
4.3 million can be allocated worldwide.
cannot connect directly to the Internet. Frames that
include private IP addresses are restricted by the
router from being sent outside the LAN.
Personal computer,
CX-Programmer, etc.
Ethernet (EtherNet/IP)
PLC
Private address
Global address
(required)
Personal computer,
CX-Programmer, etc.
PLC
Private address
Section 5-3
Private address
Not output to Internet
Not output to Internet
Private address