How does the distributed link aggregation technology used in IRF provide link redundancy?

How does the distributed link aggregation technology used in IRF provide link redundancy?
A. by enabling the Master to auto-select new forwarding paths if a link fails
B. by enabling virtual link load balancing across all known paths
C. by enabling aggregation groups to include ports on multiple switches
D. by enabling ports in an aggregation group to be placed in backup state

Correct Answer: C
Explanation/Reference:
Uplink/Downlink Backup
IRF uses a distributed aggregation technology to implement uplink/downlink backup. The traditional aggregation technology aggregates multiple physical Ethernet ports (known as member ports) to implement link backup. However, it does not have a backup mechanism for a single-point failure. The new distributed aggregation technology supported by IRF adds the physical Ethernet ports on different devices to an aggregation port group. Even if the device where some ports reside fails, the aggregation link will not become invalid. Other member devices that work normally will manage and maintain the other aggregation ports. This is of great importance to the network environments with core switching systems and having high-quality service requirements. It not only solves the problem of single-point failure of aggregation devices, but also increases availability of the entire network. As shown in Figure 11, the traffic that goes to the core network is distributed evenly on the aggregation links. When an aggregation link fails, the distributed link aggregation technology can automatically distribute the traffic to other aggregation links to implement link backup and increase network reliability.
Figure 11 Uplink/downlink backup diagram

http://www.h3c.com/portal/Products___Solutions/Technology/IRF/Technology_White_Paper/200901/624932_57_0.htm

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