Techniques are described for managing communications for a managed computer network by using a defined pool of alternative computing nodes of the managed computer network that are configured to operate as intermediate destinations to handle at least some communications that are sent by and/or directed to one or more other computing nodes of the managed computer network. For example, a manager module associated with a source computing node may select a particular alternative intermediate destination computing node from a defined pool to use for one or more particular communications from the source computing node to an indicated final destination, such as based on a configured logical network topology for the managed computer network and/or on one or more other selection criteria (e.g., to enable load balancing between the alternative computing nodes). The manager module then forwards those communications to the selected intermediate destination computing node for further handling.