A computer-implemented method, comprising: by a network controller that manages a plurality of logical networks implemented by a plurality of managed forwarding elements 'MFEs' (105, 425, 430) operating on a plurality of host machines (110, 405, 410): receiving, by the network controller, a request from a particular first MFE (105, 425) on a first host machine that an interface (115, 415), such as a virtual network interface card 'VNIC' of a first virtual machine 'VM' or other data compute node 'DCN', corresponding to a logical port of a logical forwarding element 'LFE' has connected to the particular first MFE (105, 425, 805) and has a particular logical network address in a particular logical network; assigning, by the network controller in response to the request, a physical network address to the interface (115, 415) that is unique within a physical datacenter network, wherein each of a plurality of interfaces (115, 415) connected to the particular first MFE (105, 425) is assigned a different physical network address that is unique within the physical datacenter network; storing, by the network controller, a mapping of each particular logical network address to its respective unique physical network address and distributing the mapping to the particular first MFE (105, 425) and to other MFEs including at least to a second MFE on a second host machine, wherein the first and second MFEs (425, 430) both implement the same logical network; at the particular first MFE (105, 425) on the first host machine, replacing source and destination logical network addresses with the respective unique physical network addresses according to the mapping in data messages sent from the particular logical network address to other logical network destinations; processing the data message through the physical datacenter network; and at the second MFE on the second host machine, replacing the physical network addresses with the respective logical network addresses according to the mapping and delivering the data message to a respective destination interface, such as a VNIC of a second VM. by a network controller that manages a plurality of logical networks implemented by a plurality of managed forwarding elements 'MFEs' (105, 425, 430) operating on a plurality of host machines (110, 405, 410): receiving, by the network controller, a request from a particular first MFE (105, 425) on a first host machine that an interface (115, 415), such as a virtual network interface card 'VNIC' of a first virtual machine 'VM' or other data compute node 'DCN', corresponding to a logical port of a logical forwarding element 'LFE' has connected to the particular first MFE (105, 425, 805) and has a particular logical network address in a particular logical network; assigning, by the network controller in response to the request, a physical network address to the interface (115, 415) that is unique within a physical datacenter network, wherein each of a plurality of interfaces (115, 415) connected to the particular first MFE (105, 425) is assigned a different physical network address that is unique within the physical datacenter network; storing, by the network controller, a mapping of each particular logical network address to its respective unique physical network address and distributing the mapping to the particular first MFE (105, 425) and to other MFEs including at least to a second MFE on a second host machine, wherein the first and second MFEs (425, 430) both implement the same logical network; receiving, by the network controller, a request from a particular first MFE (105, 425) on a first host machine that an interface (115, 415), such as a virtual network interface card 'VNIC' of a first virtual machine 'VM' or other data compute node 'DCN', corresponding to a logical port of a logical forwarding element 'LFE' has connected to the particular first MFE (105, 425, 805) and has a particular logical network address in a particular logical network; assigning, by the network controller in response to the request, a physical network address to the interface (115, 415) that is unique within a physical datacenter network, wherein each of a plurality of interfaces (115, 415) connected to the particular first MFE (105, 425) is assigned a different physical network address that is unique within the physical datacenter network; storing, by the network controller, a mapping of each particular logical network address to its respective unique physical network address and distributing the mapping to the particular first MFE (105, 425) and to other MFEs including at least to a second MFE on a second host machine, wherein the first and second MFEs (425, 430) both implement the same logical network; at the particular first MFE (105, 425) on the first host machine, replacing source and destination logical network addresses with the respective unique physical network addresses according to the mapping in data messages sent from the particular logical network address to other logical network destinations; processing the data message through the physical datacenter network; and at the second MFE on the second host machine, replacing the physical network addresses with the respective logical network addresses according to the mapping and delivering the data message to a respective destination interface, such as a VNIC of a second VM.