ENSURING ANY-TO-ANY REACHABILITY WITH OPPORTUNISTIC LAYER 3 FORWARDING IN MASSIVE SCALE DATA CENTER ENVIRONMENTS

Techniques are provided for updating routing tables of switch devices. At a first switch device of a first rack unit in a network, information is received about addresses of host devices in the network. The addresses are stored in a software cache. A packet is received from a first host device assigned to a first subnet and housed in the first rack unit. The packet is destined for a second host device assigned to a second subnet and housed in a second rack unit in the network. The packet is forwarded using the subnet entry and it may remain sub-optimal during a period before which an entry can be installed form a software cache. The software cache is evaluated to determine the address of the second host device. The packet is then forwarded optimally. This will ensure any-to-any communications in the network initially sub-optimally and subsequently optimally.