Techniques are described herein for optimizing communications in a network. At a router in a virtual private network, a packet is received from a device in a subnetwork protected by the router. The router examines the packet to determine a source address that identifies the device and a destination address that identifies a destination network device for the packet. The router also analyzes the packet to determine a size of the packet and determines whether or not the size of the packet is larger than a maximum transmission unit size. If the size of the packet is larger than the maximum transmission unit size, the router encapsulates the packet with a header that includes the destination address and a new source address that identifies the router.