Abstract: A communication system includes a data network that is coupled to various nodes, including routers. In one example arrangement, a first router is part of a first local network and a second router is part of a second local network. Each router includes a security gateway module and a keep-alive module. The security gateway module is capable of establishing a secure link, such as one according to an Internet Protocol Security (IPsec) protocol, over the data network. The keep-alive module sends one or more ping messages over the secure link to the remote router (or a node coupled to the router), which responds with appropriate ping replies to indicate that a link is alive.