R0106-HP MSR Router Series High Availability Configuration Guide(V7)

1
Configuring interface backup
Overview
Interface backup enables you to configure multiple backup interfaces for a Layer 3 interface to increase
link availability. When the primary interface fails or is overloaded, its backup interfaces can take over or
participate in traffic forwarding.
Compatible interfaces
The interface backup feature is configurable for the interfaces in Table 1.
Table 1 Interfaces that support interface backup
Cate
g
or
y
Interfaces Remarks
Ethernet
Layer 3 Ethernet interfaces/subinterfaces
Layer 3 VE interfaces
N/A
WAN
AM interfaces
ATM interfaces
ISDN BRI interfaces
POS interfaces
Serial interfaces (asynchronous, synchronous)
An AM interface can only work as
the backup interface. All the other
interfaces can work as both
primary and backup interfaces.
An ISDN BRI interface can work as
the primary interface only when it
is configured to provide leased line
services.
An asynchronous serial interface
cannot work as the primary
interface if DDR is configured on it.
Others
AUX ports
Dialer interfaces
MP-group interfaces
Tunnel interfaces
A dialer interface can be used as
the primary interface only when it
is a PPPoE client in permanent
session mode.
Backup modes
The primary interface and its backup interfaces can operate in strict active/standby mode or load
sharing mode.
• Strict active/standby mode—Only one interface transmits traffic. All the other interfaces are in
STANDBY state.
• Load sharing mode—Backup interfaces participate in traffic forwarding when the amount of traffic
on the primary interface reaches the upper threshold. They are activated and deactivated
depending on the amount of traffic.
In strict active/standby mode, traffic loss occurs when the active interface is overloaded. Load sharing
mode improves link efficiency and reduces the risk of packet loss.