Citrix Systems 6 manual Active-Active Bonding

This illustration shows how two NICs in a bonded pair use the same network settings, as represented by the networks in each host. The NICs in the bonds connect to different switches for redundancy.

Active-Active Bonding

Active-Active, which is the default bonding mode, is an active/active configuration for guest traffic: both NICs can route VM traffic simultaneously. When bonds are used for management traffic, only one NIC in the bond can route traffic: the other NIC remains unused and provides fail-over support.

For VM traffic, active-active mode also balances traffic. However, it is important to note that "balance" refers to the quantity (MB) of data routed on the NIC. When XenServer rebalances traffic, it simply changes which VM's traffic (more precisely, which VIF's traffic) is carried across which NIC.

While NIC bonding can provide load balancing for traffic from multiple VMs, it cannot provide a single VM with the throughput of two NICs. Any given VIF only uses one of the links in a bond at a time. As XenServer rebalances traffic, VIFs are not permanently assigned to a specific NIC in the bond. However, for VIFs with high throughput, periodic rebalancing ensures that the load on the links is approximately equal.

The illustration that follows shows the differences between the three different types of interfaces that you can bond.

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