[ILUG] Class C Addresses

[Justin Mason]

Chris Higgins said:

> > Can you name some other things that use the approach you mention?
> 
> Most half decent telnet clients I've seen will step through the 
> available IP addresses if multiple exist and one doesn't respond...

That could be more due to multi-homed host support.

It's a good trick for dealing with multi-homed hosts; if you have
2 parallel networks, one superfast and one slower, and a few
hosts on both nets, you can give them hostnames like

--------------+----------------------+------------- SUPERFAST NET
              |                      |
         host1-fast		host2-fast	   	(interfaces)
              |                      |
         HOST: host1            HOST: host2		(host)
              |                      |
         host1-slow		host2-slow	   	(interfaces)
              |                      |
--------------+----------------------+------------- SLOW NET

so e.g. host1 has interfaces "host1-fast" and "host1-slow", and the DNS A
records look like

	host1-fast	10.1.1.1
	host1-slow	10.1.2.1
	host1		10.1.1.1, 10.1.2.1

This now allows good TCP/IP clients to send packets to "host1", and cycle
through the addr list until they get a connection.  So the sysadmin
in that setup can block packets from "slow" IPs, which are connected
also to the fast network; as they know the clients will failover to
the much faster "fast" network.

Works well for connection-oriented protocols (not really HTTP).  Not great
for load balancing (as Ciaran said); much more of a win for reliability
and multi-homed host support.

--j.