
HOSTID.EXE is an executable program designed to handle 
changing which of your IP addresses are sent out to one
of your interfaces to a particular domain DNS
for resolution of your hostname on THAT domain.
In a multi-homed environment, where you have multiple interfaces
each leading to a different domain, (which are NOT connected to each other
in any way) In order for the HOSTNAME command to get your hostname from 
the DNS of a particular domain..you need to ensure that the IP
address (in that domain) is the one you send to that DNS; otherwise
the DNS can't resolv hostnames for IP's it doesn't know about.

Case in point: You ar at your business LAN which is NOT internet-connected.
1.) You have a lan0 address of 44.44.44.44 on the domain mycompany.com
2.) You SL/IP or PPP address of 191.22.2.2 on the domain internetprovider.com
3.) These two domains are NOT connected in any way...(no way of one of them
    to resolv names or IP's for the other) each with separate DNS's...

When you dial into the domain "internetprovider.com" and you change your 
default route to that domain's router..you can now call hostid.exe (with args)
to change which interface's IP address is used by the stack to retrieve your
machine's authoritative hostname from the domain where your default route points.
(This is the IP your machine will send to the domain nameserver to get your hostname).

The reason for this is SOME server applications do not "trust" a client to tell the
server what it's hostname is...the server must be able to resolv the hostname of the client
machine from a DNS (to prevent "forgery")
and it must agree with what the client says his hostname is..or else "access denied" situation
arises...or simple application failure because the client could not get his hostname,
or presented the wrong hostname to the server.

Useage:
HOSTID <ENTER>
will return your present "primary" IP. (The one presented to the DNS by SENDMAIL, and other apps)
to change your primary IP to one of your other interfaces..:
HOSTID xx.xx.xx.xx 
where: xx.xx.xx.xx is the IP of the interface to make Primary.

It is suggested that you only use this if, and when it becomes necessarry:
That is: a situation arises where a remote
server asks your client to identify itself via DNS, and then checks what you
send him against the DNS himself to make sure you are a "legitimate" machine.

It is ONLY when you are in a multi-homed environment 
(connected to multiple domains each on it's own interface)
that this situation will arise.

Otherwise, you can ignore the useage of HOSTID.EXE as you will not need it.

People most likely to need this:
People who are using SENDMAIL in multi-homed environments.
People running IRC clients connecting to an IRC server in mutli-homed environments.
People running ANY clients whose remote servers demand authoritative hostname resolution
of that client.
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