Allied Telesis AR450S Uživatelský manuál stáhnout pdf (Strana 15)

Switching on the AR440S, AR441S and AR450S 3-15

Software Release 2.6.6

C613-03079-00 REV A

transmit frames with a destination MAC address matching the entry in the

station map.

To display the contents of the Forwarding Database, use the command:

SHOW SWITCH FDB [ADDRESS=macadd][PORT={port-list|ALL}]

[STATUS={STATIC|DYNAMIC}]

To display general router settings, including settings for switch learning and

the ageing timer, use the command:

SHOW SWITCH

The Forwarding Process

The Forwarding Process forwards received frames that are to be relayed to

other ports in the same VLAN.

The destination address is then looked up in the Forwarding Database for the

VLAN. If the destination address is not found, the router floods the frame on

all ports in the VLAN except the port on which the frame was received. If the

destination address is found, the router discards the frame if the destination

address is on the same port as the source address.

The Forwarding Process provides storage for queued frames to be transmitted

over a particular port(s). More than one transmission queue may be provided

for a given port. The user priority tag in the Ethernet frame and the Quality of

Service mapping (see Quality of Service on page 3-15) determine the transmission

queue where a frame is sent.

Quality of Service

The router hardware has a number of Quality of Service (QOS) egress queues

that can be used to give priority to the transmission of some frames over other

frames on the basis of their user priority tagging. The user priority field in an

incoming frame (with value 0 to 7) determines which of the eight priority levels

the frame is allocated. When a frame is forwarded, it is sent to a QOS egress

queue on the port determined by the mapping of priority levels to QOS egress

queues. All frames in the first QOS queue are sent before any frames in the

second QOS egress queue, and so on, until frames in the last QOS egress queue,

which are sent only when there are no frames waiting to be sent in any of the

higher QOS egress queues.

The mapping between user priority and a QOS egress queue is configured

using the command:

SET SWITCH QOS=P0,P1,P2,P3,P4,P5,P6,P7

The router has four QOS egress queues. The router has a default mapping of

priority levels to QOS egress queues as defined in IEEE 802.1q (see Table 3-5 on

page 3-15).

Table 3-5: Default priority level to queue mapping for four QOS egress queues .

Priority level QOS Egress Queue

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 47 48

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