RE: Finding a specific PC IP address when dynamically assigned

Thought I'd jump in here:

If you're iSeries does the DHCP and DNS an is running at least
v5r1...Dynamic DNS is easy:
http://publib.boulder.ibm.com/iseries/v5r2/ic2924/index.htm

Prior to that, to do dynamic or "pseudo-dynamic" DNS for a network you
needed to handle DCHP and DNS on a Windows or Unix/Linux box.

Windows offered a "pseudo-dynamic" DNS at least as far back as Windows NT 4.
0  I say "pseudo-dynamic" because it was really a DNS/WINS integration that
did dynamic DNS (WINS really) updates only for Windows based PC.

Windows 2000s Active Directory allowed for true dynamic updates.


HTH,
Charles



> -----Original Message-----
> From: Scott Klement [mailto:klemscot@xxxxxxxxxxxx]
> Sent: Wednesday, March 03, 2004 1:05 PM
> To: Midrange Systems Technical Discussion
> Subject: Re: Finding a specific PC IP address when 
> dynamically assigned
> 
> 
> 
> On Wed, 3 Mar 2004, Ian Patterson wrote:
> 
> > We have an application using Scott's Socktut examples to 
> exchange data
> > between an iSeries program and our own PC program.
> > Works a treat when we know the IP address of the specific 
> PC that runs our
> > program.
> >
> > In a network where the PC's have dynamically assigned IP 
> addresses (from the
> > iSeries), is there any way to identify the IP address of a 
> particular PC ?
> 
> Well, first you have to decide how you're going to refer to 
> the PCs when
> you don't know their IP address...  obviously you can't say to the
> computer "hey, what's the address of that PC over by the 
> water cooler?"
> 
> I can think of two ways to refer to a PC when you don't know it's IP
> address, you can give it a name via DNS, or you can refer to it by MAC
> address.
> 
> The better of the two is to use dynamic DNS.  Dynamic DNS 
> means that your
> DHCP server updates the DNS server each time an IP address 
> changes.  If
> you have a computer called "Ian" (for example) and the DHCP 
> server changes
> Ian's IP address, it also tells the DNS server about the 
> change so that
> the DNS server will return the new IP address.
> 
> Then, your programs don't have to worry about what the IP 
> address is, they
> just call gethostbyname() on the word "Ian" and the system 
> does the work.
> 
> Unfortunately, I've never used an iSeries for DHCP or DNS, so 
> I don't know
> what the exact configuration directives to set up DHCP & 
> dynamic DNS are.
> 
> The second alternative is to look up the MAC address of the PC in the
> iSeries' ARP cache.   This is a much uglier solution, and 
> will only work
> if all of the PCs are on the same physical network with the iSeries.
> (Though, presumably they are if the iSeries is providing DHCP)
> 
> There's an API that can be used to list out the ARP cache, I 
> know I posted
> a sample program that uses that API somewhere...  you might 
> try searching
> the web.
> 
> Good Luck
> 
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