3Com MSR 50 Series, Руководство по настройке

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HAPTER
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ACKUP
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ENTER
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ONFIGURATION
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When a dialer interface acts as the PPPoE client and the PPPoE session works in
permanent on-line mode, it can be configured as the main interface.
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When a BRI interface is used for the ISDN leased line, it can be configured as
the main interface.
Backup interface
Backup interfaces are those functioning as backups for main interfaces (For
example, interfaces Serial 2/1 and Serial 2/2 in
Figure 578 ), which are generally
idle. A backup interface can be any physical interface.
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One backup interface can only back up one main interface.
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One main interface can be configured up to three backup interfaces.
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Up to 10 main interfaces can be configured on a device at one time.
How the Backup Center
Works
The following is how the backup center works:
Interface backup
As shown in Figure 579 , interface Serial 2/0 on Router A acts as the main interface
and interfaces Serial 2/1 and Serial 2/2 act as the backup interfaces.
Figure 579 Diagram for main/backup mode
In interface backup mode, at any given time, only one interface takes on data
transmission.
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When the main interface is operating normally, even if the traffic is overloaded,
the backup interface is in a backup state. All traffics are transmitted through
the main interface.
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Only when the main interface cannot transmit data because of interface
failure, the backup interface with a higher priority will take the main interface
instead and take on all traffic transmission.
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After the failed main interface restores, data transmission will be switched over
to the main interface. At any given time, only one interface takes on data
transmission.
Load sharing
As shown in Figure 580 , interface Serial 2/0 on Router A acts as the main
interface, and interfaces Serial 2/1 and Serial 2/2 act as the backup interfaces.
S2/1
S2/0
S2/2
Router A
Router B
LAN
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