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

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• When the primary interface fails (in DOWN state), the strict active/standby mode applies. Only
one backup interface can forward traffic.
The upper and lower thresholds are user configurable.
NOTE:
• "Traffic" on an interface refers to the amount of incoming or outgoing traffic, whichever is higher.
• If two backup interfaces have the same priority, the one configured first has preference.
As shown in Figure 2, Serial 2/1/0 on Router A is the primary interface, and Serial 2/1/1 (with a
priority of 30) and Serial 2/1/2 (with a priority of 20) are its backup interfaces.
• When the amount of traffic on Serial 2/1/0 exceeds the upper threshold, Serial 2/1/1 is activated,
because it has higher priority than Serial 2/1/2. If the amount of traffic on Serial 2/1/0 still
exceeds the upper threshold, Serial 2/1/2 is activated.
• When the total amount of traffic on all load-shared interfaces decreases below the lower threshold,
Serial 2/1/2 is first deactivated, because its priority is lower than Serial 2/1/1. If the total amount
of traffic on Serial 2/1/0 and Serial 2/1/1 is still below the lower threshold, Serial 2/1/1 is
deactivated.
Figure 2 Load sharing mode
Configuration restrictions and guidelines
When you configure interface backup, follow these restrictions and guidelines:
• The device supports up to 10 primary interfaces.
• An interface can be configured as a backup only for one interface.
• An interface cannot be both a primary and backup interface.
• For correct traffic forwarding, make sure the primary and backup interfaces have routes to the
destination network.