User manual
43
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Switch priority:
As the bridge priority
，
the bridge priority and bridge MAC address combine bridge ID, the
smallest ID bridge will become the root bridge on the network.
Polling interval:
How often send BPDU packet at one time.
Forwarding delay:
The port state of switch remains a forward delay time over the listening and learning.
The maximum aging time
: After one switch receives a packet from other switches, how long the packet
is valid.
The port concepts of RSTP:
Port path overhead:
Port link cost compared with port priority and port ID.
Port priority:
Port priority among the net bridge compared with port priority and port ID
Point to point network connection:
Directly connect with switches port each other, the port is P2P,
which adopted negotiation mechanism, RSTP can achieve port state rapid conversion RSTP
Directly connect terminal:
Connect the edge of network switch with terminal devices with configuration
Edge port, which can achieve port state rapid conversion without the processing Discarding, Learning,
Forwarding
Don’t join RST structure:
Don‟t participate in RSTP running
Four situation of RST:
Blocking:
Can receive BPDU packets to change the listening state, if the period did not receive BPDU.
Listening:
Can receive packets, after the connection to it, switches stay max age=20s in the blocking, so
judge whether switch port can become root port or designated port, the port state will convert listening
(the state remains 15 ms) if it works, receive and forward packets during this time to achieve the selection
of root for RST, structure and the direction of port. The decision is root port or specified port to convert
learning state, otherwise to convert the blocking state.
Learning
: remain forward delay (equal 15s), continue to be calculated to determine the port can become
a root port or designated port, MAC address learning function. If you decide to convert to the forwarding
state.
Forwarding:
can receive and send BPDU packet
6.4.4 IGMP-Snooping
6.4.4.1 IGMP-Snooping
IP host applies to join (or leave) multicast group to the neighboring router through IGMP (Internet Group
Management Protocol) protocol. IGMP Snooping is multicast constraining mechanism. It manages and
controls multicast group by snooping and analysis of the IGMP messages between the host and the
multicast device.
Work process of IGMP Snooping: the switch snoops messages between the host computer and the router
and tracks multicast information and the port applied for. When the switch snoops IGMP Report message
sent from the host computer to the router, the switch would add this port to multicast forwarding list; when