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A. Technical appendix
A-4
Festo P.BE-SBO-Q-EN en 1602e
A.2 Addressing in the Ethernet (basics)
Due to the separation into logical and physical protocol layers
(Ethernet and TCP/IP ), there are two types of addresses in a
network:
– a fixed Ethernet address (MAC ID) for each device and
– an IP address which is assigned to every device in the
network.
From the application, data are always sent to or received from
an IP address. In order that the data reach the receiver, a link
must be created between the logical IP address and the
physical Ethernet address. The Address Resolution Protocol
ARP is used for this purpose: An ARP table is saved in each
network PC. This table lists the relevant physical Ethernet
address for each IP address in the network. If an Ethernet
address is not listed in the ARP table, the IP driver can
ascertain it with the aid of an ARP request.
Ethernet address (MAC ID) The unchangeable, globally unique Ethernet address
(MAC-ID) of the Compact Vision System can be found on the
type plate. In this way you can clearly distinguish between
the different Compact Vision Systems.
IP address An IP address as per the IPv4 standard is usually expressed
as 4 decimal numbers separated by dots (each 1 byte).
Example of an IP address: 192.168.2.10
An IP address addresses both a network and an individual
slave in the network. The IP address therefore contains:
– the net ID (specifies the address of a network) and
– the host ID (specifies the address of an individual slave
in this network).