Providing logical networking functionality for managed computer networks

A computer-implemented method for providing logical networking functionality for computer networks, the method comprising:

• receiving configuration information for a first virtual computer network that includes multiple computing nodes arranged via a specified network topology, the multiple computing nodes each having a distinct virtual network address for the first virtual computer network, the configuration information indicating one or more specified networking devices that interconnect the multiple computing nodes and that are each associated with one or more of the multiple computing nodes;
• and
• under control of one or more configured computing systems, automatically providing the first virtual computer network in accordance with the received configuration information by overlaying the first virtual computer network on a distinct substrate network and by emulating the specified network topology for multiple communications between the multiple computing nodes without physically implementing the specified network topology, the multiple communications each being sent from a sending one of the multiple computing nodes to one or more of the multiple computing nodes that are each a destination computing node for the communication, each communication including a virtual network address corresponding to the one or more destination computing nodes and including a virtual hardware address associated with one of the specified networking devices that is an initial intermediate destination of the communication, the emulating of the specified network topology including, for each of the multiple communications:
• identifying the one or more destination computing nodes based on the virtual network address included in the communication;
• and
• for each of the one or more destination computing nodes,
• forwarding the communication over the substrate network to a location of the destination computing node;
• modifying the communication to include information corresponding to the communication having been forwarded via the specified network topology from the sending computing node to the destination computing node by the specified networking device whose associated virtual hardware address is included in the communication;
• and
• providing the modified communication to the destination computing node.

A computer-readable medium whose contents enable a computing system to provide logical networking functionality for computer networks, by performing a method comprising:

• obtaining information regarding a specified logical network topology for a first virtual computer network that includes multiple computing nodes, the first virtual computer network being overlaid on a distinct substrate network that interconnects the multiple computing nodes, each of the multiple computing nodes having an associated virtual network address for the first virtual computer network and having a distinct associated substrate network address that corresponds to a location of the computing node in the substrate network;
• and
• automatically managing multiple communications sent between the multiple computing nodes so as to virtually implement the specified logical network topology for the first virtual computer network, the multiple communications each being sent from a first computing node and including the virtual network address for a destination second computing node, the managing of each of the multiple communications including:
• using the substrate network address associated with the second computing node to forward the communication over the substrate network to the location of the second computing node in the substrate network;
• and
• before providing the communication to the second computing node, modifying the communication to include information emulating forwarding of the communication from the first computing node to the second computing node via the logical network topology.

A system structured to provide logical networking functionality for computer networks, comprising:

• one or more processors of one or more computing systems;
• and
• one or more communication manager modules that are each configured to, when executed by at least one of the one or more processors, provide logical networking functionality for a first virtual computer network that is implemented using one or more intermediate networks, the one or more intermediate networks including multiple physical networking devices that physically interconnect multiple computing nodes of the first virtual computer network, each of the multiple computing nodes having an associated first virtual network address for the first virtual computer network and having a distinct associated second network address that corresponds to the one or more intermediate networks, the providing of the logical networking functionality including:
• obtaining configuration information regarding one or more specified logical networking devices of the first virtual computer network that logically interconnect the multiple computing nodes and that are distinct from the physical networking devices of the one or more intermediate networks;
• and
• automatically managing multiple communications sent between the multiple computing nodes so as to implement functionality of the specified logical networking devices, the managing of each of the multiple communications including using the second network address of a destination computing node for the communication to forward the communication via at least one of the physical networking devices of the one or more intermediate networks to the destination computing node, the managing of each of the multiple communications further including modifying the communication to include information emulating forwarding of the communication by one or more of the specified logical networking devices that logically interconnect the multiple computing nodes.