Seamless split-horizon flooding of layer two (L2) network traffic on non-native and mixed architectures

A forwarding component of a routing node floods copies of a packet to a plurality of next hops associated with the same layer two (L2) network as an interface on which the packet was received. The plurality of next hops excludes a next hop that corresponds to the interface that received the packet. The forwarding component requires that forwarding information installed by a control unit specify the plurality of next hops to which to flood the copies of the packet, and the forwarding component is not capable of deriving the plurality of next hops to which to flood the copies of the packet from a single flooding next hop identifier after the packet is received. Prior to receiving the packet, a flooding next hop control module derives the plurality of next hops based on the flooding next hop and installs the derived next hops into the forwarding information.