RAD Data comm LRS-24 - Manual (Page 100)

Appendix C SNMP Management LRS-24 Installation and Operation Manual
C-6 IP Environment
Net and Subnet Masks
Net and subnet masks are used to help filter the relevant traffic more efficiently:
the function of the net and subnet mask is to specify how many of the IP address
bits are actually used for the net identifier and for the subnet number.
The mask is a 32-bit word that includes ones in the positions used for net and
subnet identifications, followed by zeros up to the end of the IP address.
Therefore, a subnet mask can be specified by its length (the number of ones).
Assignment of Addresses
The CM-2 module and the I/O modules installed in the LRS-24 must be assigned
consecutive IP addresses: the first (lowest) address must be assigned to the CM-2
module, and the following 12 IP addresses must be reserved for the I/O modules
(the first address is associated with I/O slot 1, and the last address with slot 12).
Unused addresses must be skipped: that is, when an I/O module with internal
SNMP agent is configured, it must be assigned the IP address corresponding to the
slot in which it is installed, even if previous addresses are not assigned.
Default Gateway
When the CM-2 module and the network management station are both
connected to the same IP network, the network identifier part of the CM-2 IP
address must be identical to the network identifier part of the management station
IP address.
However, the CM-2 module and the management station can also be on different
IP networks, and therefore each one will be assigned IP addresses according to its
IP network. In this case, it is necessary to define a default gateway (IP router) for
the CM-2 module, to handle the transfer of management traffic between the CM-2
and the management station.
Handling of Management Communication
The handling of the management communication within the CM-2 module
depends on the type of management communication (ASCII terminal, SLIP, or
UDP/IP) and the type of modules (with or without internal SNMP agent) which are
addressed by the external management function.
Modules with Internal SNMP Agent
This section describes the handling of the SNMP management communication
when this communication is related to modules with internal SNMP agents.
For such modules, the management communication is internally transferred using
SNMP over SLIP. The SNMP management communication is handled as follows:
• SNMP messages over UDP/IP (the protocol used when a network management
station is connected through the dedicated management interface on the
Ethernet interface modules) are converted to the SLIP protocol.
• SNMP messages over SLIP (the protocol used when a network management
station is connected through the serial supervisory port of the CM-2 module),
are routed to the addressed module.
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