This section describes issues regarding IP services and starts with a discussion about IP addressing. Even when Layer 2 connectivity is intact, failures at Layer 3 prevent communication.
IP addresses identify interfaces, not devices. The principal IP parameters are address, subnet mask, and (except on routers) default gateway. Addresses are unique, but a mask and gateway should be common on a subnet. Address information can be either statically assigned or obtained from Dynamic Host Configuration Protocol (DHCP).
When troubleshooting IP connectivity, refer to the following steps:
Step 1. Use traceroute to test connectivity or (if broken) the last point working in the path.
Step 2. ...