For example if we have 2 (or more) physical interfaces how to connect them to different network segments and, if one of the segments fails, the second network interface to step in automatically?
Remark: You may need to read the article 5480 (How to set up the redundant network connection for a NetApp array?) first.
A single-mode VIF contains a single active link and a number of links in passive mode. All links in the single-mode VIF share a single MAC address. Only one link is active and sending data therefore there is never a duplicate MAC address on the network. A single-mode VIF is configured with two links connected to redundant switches. Only link e0 is active, while the e1 is in standby mode. If e0 fails (signalled by the link status of the interface going down), the remaining link will take over. In the case of multiple standby interfaces, the storage device will randomly pick one to bring up as the active link. This is commonly known as active passive mode. (source NetApp Technical report TR3802).