The following are general guidelines for troubleshooting network connectivity and configuration issues.
One of the first signs of trouble on a network is loss of communications by one or more of the hosts. If a host does not to come up the first time it is added to the network, the problem might be a faulty NIC or a problem with network daemon that is managed by SMF.
If a single host that previously was connected to the network suddenly develops a network problem, the problem could be the system's network interface configuration. If the hosts on a network can communicate with each other but not with other networks, the problem could be the router. Another problem could be with the other network.