Supermicro AOC-XEH-IN2 Uživatelský manuál stáhnout pdf (Strana 86)

Superblade Network Modules User’s Manual

6-22

root switch will set a Topology Change flag in its normal BPDUs. This flag is propagated

to all other switches to instruct them to rapidly age out their forwarding table entries.

Port Transition State

When a device is connected to an RTSP or STP enabled switch port for the first time, it

will not immediately start to forward data. Instead, it will go through a number of states

while it processes BPDUs and determines the network topology.

There are five port states in the legacy 802.1d STP: disabled, blocking, listening,

learning and forwarding. The RSTP combines the disabled, blocking and listening states

used in 802.1d STP and creates a single state: Discarding. Table 6-7 lists the

comparison of port states between 802.1d STP and 802.1w RSTP.

RSTP Port Roles

RSTP will assign port roles for each port during the process receiving the BPDUs.

Based on its port role, a port can either send or receive BPDUs and forward or block

data traffic.

• Root – the port that provides the lowest cost path when the switch forwards packets

to the root switch.

• Designated – the port closest to the root switch and forwarding traffic toward the

root switch and sending BPDUs in a link segment. Each designated port is in a

forwarding state.

• Alternate – this port provides an alternate path to the root bridge. This path is

different than using the root port. The alternate port is in a blocking state.

• Backup – the port provides a backup/redundant path to a link segment to which

another switch port already connects. This is a special case when two or more ports

of the same switch are connected together.

• Disabled - Not a strictly part of RSTP, a network administrator can manually disable

a port.

To configure the R

APID SPANNING TREE, click the SPANNING TREE folder on the left-hand

side bar. There are two portions to configure: RSTP S

WITCH SETTINGS and RSTP PORT

ETTINGS, as shown in the RAPID SPANNING TREE screen (Figure 6-18).

Table 6-7. Comparison of Port States

State Displayed 802.1d STP 802.1w RSTP

Discarding Disabled Discarding

Discarding Blocking Discarding

Discarding Listening Discarding

Learning Learning Learning

Forwarding Forwarding Forwarding

1 2 ... 81 82 83 84 85 86 87 88 89 90 91 ... 391 392

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