The best way to approach this problem is to query each possible IP address on the LAN to see if a host responds. There are several utilities that will do this for you. First, of course, is the venerable ping utility. Most ping implementations can query only a single host at a time, so a completely automated search would require calling ping from a script. Fortunately, there are more convenient solutions. The fping utility can send a ping to a range of addresses or to a whole subnetwork with a single invocation. For example, to ping every address on the 192.168.3.X subnet, we would invoke fping as
fping -g 192.168.3.0/24or
fping -g 192.168.3.1 192.168.3.254
Another, more flexible, tool is nmap. Because it is intended primarily as a security testing tool, nmap is adept at finding hosts on a network. To query the same subnet as in the fping example, we would invoke nmap as
nmap –sP 192.168.3.0/24
All of the utilities that we discussed above are open source and available for Unix/Linux, MAC, and Windows. Because many system administrators configure network firewalls to filter ICMP ping packets, it is best to run these tools from a host on the LAN you are testing.
Dig Deeper on Campus area networks and services
Related Q&A from Jon Snader
Learn how to set an IP address on the network interface of a FTP/Web/mail server when a client has only one public IP address. Continue Reading
To connect to a WAN remotely, your client can use a VPN client or a leased line. Learn the pros and cons of WAN connectivity with each option, such ... Continue Reading
When using ISA 2000, some users can lose connection to the network and experience packet loss even if the VPN client is still connected. Learn how ... Continue Reading
Have a question for an expert?
Please add a title for your question
Get answers from a TechTarget expert on whatever's puzzling you.