How to configure HA/load-balancing at L3 for multiple NICs with quagga route injection and loopback addr (centos 7)

In a previous post this was mentioned by @Celada in the Enhanced version section: https://unix.stackexchange.com/questions/255923/use-nic-bonding-with-independent-switches My situation: one centos 7.2 host with 4 100G NICs - all connected to ToR: NIC1: 10.0.2.1/24 NIC2: 10.0.2.2/24 NIC3: 10.0.2.3/24 NIC4: 10.0.2.4/24 Requirement: How to configure an extra loopback addr on the centos host and publish it as a single IP for HA/LB access for client machines within the rack, for iSCSI data-path access for storage.