5 GENERIC FUNCTIONS FOR REDUNDANT ETHERNET BOARDS
The following functions apply to all redundant Ethernet protocols.
5.1 FORWARDING
The MiCOM ALSTOM Ethernet switch products support store and forward mode. The switch forwards
messages with known addresses to the appropriate port. The messages with unknown addresses, the
broadcast messages and the multicast messages are forwarded out to all ports except the source port.
MiCOM ALSTOM switches do not forward error packets, 802.3x pause frames, or local packets.
5.1.1 PRIORITY TAGGING
802.1p priority tagging is enabled on all ports.
5.2 SIMPLE NETWORK MANAGEMENT PROTOCOL (SNMP)
Simple Network Management Protocol (SNMP) is a network protocol designed to manage devices in an IP
network. SNMP uses a Management Information Base (MIB) that contains information about parameters to
supervise. The MIB format is a tree structure, with each node in the tree identified by a numerical Object
Identifier (OID). Each OID identifies a variable that can be read or set using SNMP with the appropriate
software. The information in the MIB is standardized.
Each system in a network (workstation, server, router, bridge, etc.) maintains a MIB that reflects the status of
the managed resources on that system, such as the version of the software running on the device, the IP
address assigned to a port or interface, the amount of free hard drive space, or the number of open files. The
MIB does not contain static data, but is instead an object-oriented, dynamic database that provides a logical
collection of managed object definitions. The MIB defines the data type of each managed object and
describes the object.
The SNMP-related branches of the MIB tree are located in the internet branch, which contains two main
types of branches:
● Public branches (mgmt=2), which are defined by the Internet Engineering Task Force (IETF).
● Private branches (private=4), which are assigned by the Internet Assigned Numbers Authority (IANA).
These are defined by the companies and organizations to which these branches are assigned.
The following figure shows the structure of the SNMP MIB tree. There are no limits on the width and depth of
the MIB tree.
Chapter 8 - Redundant Ethernet MiCOM P747
252 P747-TM-EN-1
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