@param context - sender context, to match reply w/ request
@param is_add - 1 to add neighbor, 0 to delete
@param is_ipv6 - 1 for IPv6 neighbor, 0 for IPv4
+ @param rx_sw_if_index - specify the original RX interface of traffic
+ that should be redirected. ~0 means any interface.
@param tx_sw_if_index - the TX interface to which traffic shoulde be
redirected.
@param nh - The next-hop to redirect the traffic to.