H3C Technologies H3C MSR 50 - Manual (Page 20)

12
Configuring interface backup
Overview
Interface backup increases network reliability. The active interface transmits services, and the standby
interfaces are in the backup state. When the active interface fails or the link fails, or when the traffic on
the active interface exceeds the configured threshold, a standby interface is activated to transmit
services.
As shown in
Figure 4 , interfaces Serial 2/0, Serial 2/1, and Serial 2/2 on Router A back up each other.
Serial 2/0 transmits data, and Serial 2/1 and Serial 2/2 are standby interfaces that have different
priorities.
Figure 4 Diagram for interface backup
When interface Serial 2/0 or its link to Router B fails, or when the traffic on Serial 2/0 exceeds the
configured threshold, the standby interface with the highest priority is activated, ensuring uninterrupted
data transmission.
Active and standby interfaces
In interface backup, an interface can be an active interface or standby interface. Interfaces that can
serve as active or standby interfaces are: Layer 3 Ethernet interfaces, Layer 3 Ethernet subinterfaces,
synchronous serial interfaces, asynchronous serial interfaces, AM interfaces, AUX ports,
WLAN-ETHERNET interfaces, dialer interfaces, ISDN BRI interfaces, Layer 3 VE interfaces, ATM
interfaces, POS interfaces, Tunnel interfaces, USB 3G Modem interfaces, and MP-group interfaces.
Active interface—An active interface transmits data, and can be configured with up to three standby
interfaces (for example, Serial 2/0 in Figure 4 ). Up to 10 active interfaces can be configured on a
device.
• When a Dialer interface acts as the PPPoE client and the PPPoE session operates in permanent
on-line mode, it can be configured as the active interface.
• When a BRI interface is used for the ISDN leased line, it can be configured as the active interface.
Standby interface—Standby interfaces function as backups for active interfaces (for example, interfaces
Serial 2/1 and Serial 2/2 in Figure 4 ), which are generally idle. One standby interface can only back
up one active interface.