SI-Ethernet User Guide 19
Issue: 3
Safety
information
Introduction
Mechanical
installation
Electrical
installation
Getting started
Parameters
Key features
and Protocols
PC Tools
Applications
Security Diagnostics
Glossary of
terms
Index
5.6.1 The IP address
The IP address is made up from four 8 bit decimal numbers (octets) and is written as follows:
w.x.y.z for example192.168.0.1 (class c)
5.6.2 The subnet mask
The subnet mask defines what part of the address constitutes the subnet within the IP address and
what part of the address constitutes the host address. The subnet mask is bit-wise ANDed with the
address to give the subnet to which the host belongs. A typical class C subnet mask would be
255.255.255.0, this may alternatively be written as ‘/24’ as in the example below, showing an IP
address of 192.168.0.1 with a subnet mask of 255.255.255.0. This alternative notation indicates the
number of bits representing the subnet part of the address, starting from the most significant bit.
Alternative subnet mask notation: 192.168.0.1 /24
5.6.3 Completing the address
To determine which part of the address constitutes the network address and which part constitutes
the node address, the IP address is bit-wise ANDed with the subnet mask. Figure 5-1 shows how
the IP address and subnet mask are used to determine the subnet address and the host address.
Figure 5-1 Completing the address
5.7 DHCP considerations
5.7.1 Using fixed IP addressing
Using fixed IP addresses (manually configured) means that if a module fails, the IP address can be
restored to a replacement module without the need to reconfigure the DHCP server. Using fixed
addresses also prevents the DHCP server from changing the address. When using fixed IP
addresses, it is vital that the IP address is reserved on the DHCP server to prevent duplicate
addressing.
If using manual IP address configuration please note that the IP address subnet mask
and the default gateway must also be set manually. For more information on manual
configuration see section 7.2.6 Network on page 22.
IP Address
Subnet Mask
Subnet Address
Host
Address
bit-
To Next Page
Loading...
Need help?
General
