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DES-3326 Layer 3 Fast Ethernet Switch User’s Guide
• Authentication Failure This trap signifies that someone has tried to logon to the
switch using an invalid SNMP community string. The switch automatically stores the
source IP address of the unauthorized user.
• Topology Change A Topology Change trap is sent by the Switch when any of its
configured ports transitions from the Learning state to the Forwarding state, or from
the Forwarding state to the Blocking state. The trap is not sent if a new root trap is
sent for the same transition.
• Link Change Event This trap is sent whenever the link of a port changes from link
up to link down or from link down to link up.
• Port Partition This trap is sent whenever the port state enters the partition mode (or
automatic partitioning, port disable) when more than thirty-two collisions occur while
transmitting at 10Mbps or more than sixty-four collisions occur while transmitting at
100Mbps.
• Broadcast\Multicast Storm This trap is sent whenever the port reaches the
threshold (in packets per second) set globally for the switch. Counters are maintained
for each port, and separate counters are maintained for broadcast and multicast
packets. The switch’s default setting is 128 kpps for both broadcast and multicast
packets.
MIBs
Management and counter information are stored in the Switch in the Management Information Base
(MIB). The Switch uses the standard MIB-II Management Information Base module. Consequently,
values for MIB objects can be retrieved from any SNMP-based network management software. 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 port
and type 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 enters the relationship between destination MAC or IP addresses and the Ethernet port or
gateway router the destination resides on into its forwarding table. This information is then used to
forward packets. This reduces the traffic congestion on the network, because packets, instead of being
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