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Gigabit Ethernet Switch User's Guide
MIBs
The information stored in the Switch is known as the Management Information Base (MIB). The Switch uses
the standard MIB-II Management Information Base module. Consequently, MIB values inside the Switch can
be retrieved from any SNMP-based network manager. In addition to the standard MIB-II, the Switch also
supports its own proprietary enterprise MIB as an extended Management Information Base. These MIBs may
also be retrieved by specifying the MIB's Object-Identity (OID) at the network manager. MIB values can be
either read-only or read-write.
Read-only MIBs variables can be either constants that are programmed into the Switch, or variables that
change while the Switch is in operation. Examples of read-only constants are the number of ports and types
of ports. Examples of read-only variables are the statistics counters such as the number of errors that have
occurred, or how many kilobytes of data have been received and forwarded through a port.
Read-write MIBs are variables usually related to user-customized configurations. Examples of these are the
Switch's IP Address, Spanning Tree Algorithm parameters, and port status.
If you use a third-party vendors' SNMP software to manage the Switch, a diskette listing the Switch's
propriety enterprise MIBs can be obtained by request. If your software provides functions to browse or modify
MIBs, you can also get the MIB values and change them (if the MIBs' attributes permit the write operation).
This process however can be quite involved, since you must know the MIB OIDs and retrieve them one by one.
Packet Forwarding
The Switch looks at the network configuration to forward packets. This reduces the traffic congestion on the
network, because packets, instead of being transmitted to all segments, are transmitted to the destination
only. Example: if Port 1 receives a packet destined for Port 2, the Switch transmits that packet through Port
2 only, and transmits nothing through Port 1.
Filtering Database A Switch filters frames, i.e., does not relay frames received by a Switch port to
other ports on that Switch, in order to prevent the duplication of frames. Frames transmitted between a
pair of end stations can be confined to LANs that form a path between those end stations.
The functions that support the use and maintenance of filtering database information are:
1. Permanent configuration of reserved addresses.
2. Explicit configuration of static filtering information.
3. Automatic learning of dynamic filtering information through observation of Switched Local Area
Network traffic.
4. Aging out of filtering information that has been automatically learned.
5. Calculation and configuration of Switched Local Area Network topology.
Aging Time
The Aging Time is a parameter that affects the auto-learn process of the Switch in terms of the network
configuration. Dynamic Entries, which make up the auto-learned-node address, are aged out of the address
table according to the Aging Time that you set.
The Aging Time can be from 10 to 1,000,000 seconds. A very long Aging Time can result with the out-of-date
Dynamic Entries that may cause incorrect packet filtering/forwarding decisions.
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