Multicast

Chapter 5 Configuring the Switch

Spanning Tree > MSTP Interface Settings > MSTP Port Setting Detail

Designated Cost The cost for a packet to travel from this port to the root in the current SpanningTree configuration.. The slower the media, the higher the cost..

Designated 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..

Designated Bridge 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 Priority 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

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..

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