Using PING <address> you can see if an address is reachable on your network, assuming the firewall allows the echo.

What functions could I use to write a network monitor which would alert me when one of a list of interfaces became unreachable? Raw sockets are required here, right? Or am I off track already?

Windows 2000 would be the platform for the utility.

Raw sockets would work. You just need to use the regular winsock functions, they work much like an udp socket except that you include the headers in your buffer.

There's also a special DLL that handles only the special case of sending / receiving ICMP for pings. It has long been undocumented by Microsoft, but highly compatible between operating systems. It might be documented somewhere now.

Iphlpapi lets you send pings. Incidentally it's interface is the same as icmp.dll's.

It seems to me that the only way of doing it is polling with ping, or something similar to ping.

If you don't get a good solution by Monday, I'll find out from the guys at work how they tell. We have a really cool siren that goes off when one of our servers goes down :-D

[quote author=iago link=board=5;threadid=8588;start=0#msg79598 date=1094861200]
It seems to me that the only way of doing it is polling with ping, or something similar to ping.

If you don't get a good solution by Monday, I'll find out from the guys at work how they tell. We have a really cool siren that goes off when one of our servers goes down :-D
[/quote]

If there's a cheapo package out there already, I'm interested. Otherwise I'll throw something together using IPHLPAPI.

I finally remembered to ask about this.  We use a program called "What's Up".  I have no idea how it works or if it costs anything to license, but it can be found here:

http://www.cns.yorku.ca/comnews/unixtools.htm

[quote author=iago link=topic=8588.msg82426#msg82426 date=1096391149]
I finally remembered to ask about this.  We use a program called "What's Up".  I have no idea how it works or if it costs anything to license, but it can be found here:

http://www.cns.yorku.ca/comnews/unixtools.htm
[/quote]
The NOC here uses it.  I believe IPSwitch is the manufacturer.

I used to have WhatsUpGold for Windows 2000, but deleted/lost it a year or two ago.