Linksys SRW224G4P - Manual (Page 46)

Chapter Configuring the Switch
42 24-Port 10/100 + 4-Port Ggabt Swtch wth WebVew and Power over Ethernet
Spanning Tree > MSTP Interface Settings > MSTP Port Setting Detail
Desgnated Cost The cost for a packet to travel from this
port to the root in the current Spanning Tree configuration .
The slower the media, the higher the cost .
Desgnated Port The port priority and number of the
port on the designated bridging device through which the
Switch must communicate with the root of the Spanning
Tree .
Desgnated Brdge The bridge priority and MAC address
of the device through which this port must communicate
to reach the root of the Spanning Tree .
Path Cost This parameter is used by the STP to determine
the best path between devices . Therefore, lower values
should be assigned to ports attached to faster media, and
higher values assigned to ports with slower media . (Path
cost takes precedence over port priority .) Note that when
the Path Cost Method is set to “short,” the maximum path
cost is 65,535 .
Range –
Ethernet: 200,000-20,000,000
Fast Ethernet: 20,000-2,000,000
Gigabit Ethernet: 2,000-200,000
Default –
Ethernet – Half duplex: 2,000,000; full duplex: 1,000,000;
LAG: 500,000
Fast Ethernet – Half duplex: 200,000; full duplex: 100,000;
LAG: 50,000
Gigabit Ethernet – Full duplex: 10,000; LAG: 5,000
Interface Prorty Defines the priority used for this port
in the Spanning Tree Protocol . If the path cost for all ports
on a switch are the same, the port with the highest priority
(i .e ., lowest value) will be configured as an active link in
the Spanning Tree . This makes a port with higher priority
less likely to be blocked if the Spanning Tree Protocol is
detecting network loops . Where more than one port is
assigned the highest priority, the port with lowest numeric
identifier will be enabled .
Default: 128
Range: 0-240, in steps of 16
Multicast
The Internet Group Management Protocol (IGMP) runs
between hosts and their immediately adjacent multicast
router/switch . IGMP is a multicast host registration
protocol that allows any host to inform its local router that
it wants to receive transmissions addressed to a specific
multicast group .
A router, or multicast-enabled switch, can periodically ask
their hosts if they want to receive multicast traffic . If there
is more than one router/switch on the LAN performing IP
multicasting, one of these devices is elected “querier” and
assumes the role of querying the LAN for group members .
It then propagates the service requests on to any adjacent
multicast switch/router to ensure that it will continue to
receive the multicast service .
Based on the group membership information learned
from IGMP, a router/switch can determine which (if any)
multicast traffic needs to be forwarded to each of its ports .
At Layer 3, multicast routers use this information, along
with a multicast routing protocol such as DVMRP or PIM,
to support IP multicasting across the Internet .
NOTE: IGMP neither alters nor routes IP
multicast packets . A multicast routing protocol
must be used to deliver IP multicast packets
across different subnetworks .