S Layer 2 Managed Switch User Manual
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MaxAge to FwdDelay (Notice: In default, MAC address item MaxAge is 300 seconds). This mechanism intend enable switch
clear old MAC address item (there might be some MAC addresses items are not correct due to network change) and let
switch learn new MAC address item when network changes.
4.7.2 Spanning tree’s ports status
In terms of there is some delay when BPDU message transfer in the network, if some interface status in spanning tree
changes from non-involved role to direct forwarding status, it might brings temporarily data loopback. Thus the interface
must wait to forward data frame until new topology message is transferred to the whole network.
There are statuses below for every second level interface in every Spanning tree:
Blocking—after the interface is in use, it enter Blocked status first before listening network. Interface drops data frame
from some network section or other ports but receives BPDU message and submit it to STP for processing. It will not
send BPDU message, receive and process network management message.
Listening—when STP determines the interface should be involved in data forwarding, listening is the first status.
Interface drops data frame that comes from some network section or other port. It does not learn MAC address but
receives and processes BPDU message and network management message. Switch accomplishes three tasks during this
process: 1) elect root bridge; 2) elect root port in Non-root Bridge; 3) Assign port to every network section. The ports
those are elected as root port, designated port turn to learning status while other ports return to blocking status.
Learning—interface prepares for data forwarding. Interface drops data frame from some network section or other port
but learns MAC address; it receives and processes BPDU message and network management message. Switch processes
and generates BPDU message in this status.
Forwarding—Interface forwards data frame that comes from some network section or other port, learns MAC address,
receives and processes BPDU message and network management information.
Disabled—Interface is not involved in spanning tree (the reason might be interface is closed, there is no interface in the
chain or there is no STP running on the interface etc.).
Notice: To STP Bridge’s parameters configuration, we must follow the rules below:
MaxAge<=2X (forwardDelay-1)
MaxAge>=2X (he1)
4.8 SNMP and RMON management
4.8.1 SNMP protocol
SNMP is simple network management protocol. It is the most widely used network management protocol including 5 main
functions: malfunction management, billing management, configuration management, performance management, security
management. It provides the format of communication between network management application software and network
agent.
There are four factors in SNMP protocol: management station, management agent, management information store, network
management protocol. Management agent is the server when management station visits switch. Management station visits
switch through network management protocol while the entity that management station visits switch is management
information store. Management information store organizes in switch as MIB mode.
Management station:
Generally there is network management software running on management station. Some popular general network
management tools are HP openview, Snmpc etc. In addition, every network device manufacturer would provide its own
network management tools in order to management network equipments.
S
supports general SNMP network
management tool.
