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Re: The i and DHCP



fixed

The way DHCP leases work is that when they are HALF done, the client begins attempting to negotiate an extension. So long as the DHCP server is still running and the IP addresses the client is using is still a valid IP for the DHCP server the client will simply extend it's lease. During continuous use only if the IP address is no longer valid for the server will the client get a new address. As a consequence a typical device may have the same address for it's entire life!

Think about the consequences of a device simply getting a new IP address at 3:09:18 in the afternoon while transmitting payroll to the bank, or sending a large file to the file server, or downloading a large file from repository, or any HTTPS connection, or SSH connection, or for that matter TN5250 :-)

- Larry "DrFranken" Bolhuis.


On 10/4/2012 2:52 PM, John McKee wrote:
I sent this to our network engineer:

When a lease expires, does it automatically renew? Or, could the
computer get a new IP address even if there was an active connection.


His response:

Yes to both.



Which takes me back to the original premise that a computer, using
DHCP to acquire an IP address, could well have it get changed. I am
thinking there isn't much that could be done. I guess the job could
be disconnected if there was a network break. But, how could the
workstation, potentially with a new IP address, reconnect to the old
job?

As I said at the top, this is dying in about a month. But, doesn't
this happen at other places? What happens when it does?

John McKee

On Thu, Oct 4, 2012 at 12:12 PM, <rob@xxxxxxxxx> wrote:
We used to downgrade to XP also. But with newer laptops having too much
memory for XP we decided to go to W7. I hated using it on my wife's
laptop but now I've gotten a little fond of it.


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: John McKee <jmmckee@xxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
Date: 10/04/2012 11:36 AM
Subject: Re: The i and DHCP
Sent by: midrange-l-bounces@xxxxxxxxxxxx



The "official" stated reason for leaving computers running 24/7 was to
push out various updates. How often is that done? Rarely. We just
had a push install of IE 8, One of my computers is Windows 2000.
Other is XP. Almost no Windows 7 here. New computers get immediately
downgraded to XP. Leaving computers on doesn't make a lot of sense.
Except the pc people get to replace failed hard drives.

AFAIK, no computers are backed up. Just network servers.

John McKee

On Thu, Oct 4, 2012 at 9:59 AM, <rob@xxxxxxxxx> wrote:
We tell all people to leave their desktop's on 24x7. We use TSM to back
them up at times of least usage. And it can't back all clients up at
the
same time so it staggers around. One problem with laptops is that
people
tend to take them home. "Why does my performance suddenly suck?" Reply:
Backup just kicked in. Fixing that with Remote Desktop.


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: John Jones <chianime@xxxxxxxxx>
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
Date: 10/04/2012 10:54 AM
Subject: Re: The i and DHCP
Sent by: midrange-l-bounces@xxxxxxxxxxxx



Unless the DHCP server is misconfigured. The norm is to auto-renew an
address' lease. Say the lease time is 24 hours. When the 24 hours is
up,
does the address lease expire (causing a new address to be assigned) or
does it auto-renew for another lease period (another 24 hours)? I've
never
seen an environment where the lease doesn't auto-renew.

Tell the network person to pay the electric bill if they thinks its
reasonable to leave devices on 24/7.

One other thought: Are the PCs built from an image? If so, are they
being
set up with identical MAC addresses? To track which machines have what
IP
addresses the DHCP server maps IPs to MAC addresses so duplicate MACs
might
cause random issues with DHCP services.


On Thu, Oct 4, 2012 at 9:30 AM, <rob@xxxxxxxxx> wrote:

What we're saying is that we don't suspect it's the DHCP timeout.


Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: John McKee <jmmckee@xxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion
<midrange-l@xxxxxxxxxxxx>,
Date: 10/04/2012 10:16 AM
Subject: Re: The i and DHCP
Sent by: midrange-l-bounces@xxxxxxxxxxxx



Wireless laptops exist here. However, most of the computers I have
dealt with are still wired. Our network person has decreed that all
computers be left on at all times. What I could guess is that a new
DHCP lease could get assigned at 8:20 AM, while somebody was connected
to the i and working well from 7:50AM. Suddenly, a dead connection.
This morning alone, there have been three. User can't reconnect, as
that session is "in use" all because the IP address changed. End the
orphan job, potentially reset the device, and all is well.

Guess what I am wondering is how other systems handle this so that
users are unaware of the IP address switch, and if the i has a way to
deal with this. We are terminal at v5r4.

John McKee

On Thu, Oct 4, 2012 at 8:57 AM, <rob@xxxxxxxxx> wrote:
All of our clients use DHCP. I did
WRKACTJOB SBS(QINTER) SEQ(*NUMBER)

Here's a couple of jobs
Entered system:
Date . . . . . . . . . . . . . . . . . . : 09/22/12
Time . . . . . . . . . . . . . . . . . . : 03:39:00
Entered system:
Date . . . . . . . . . . . . . . . . . . : 09/28/12
Time . . . . . . . . . . . . . . . . . . : 07:49:02
Entered system:
Date . . . . . . . . . . . . . . . . . . : 10/01/12
Time . . . . . . . . . . . . . . . . . . : 05:41:15

You sure they aren't using wireless laptops and roaming through dead
spots
or something?



Rob Berendt
--
IBM Certified System Administrator - IBM i 6.1
Group Dekko
Dept 1600
Mail to: 2505 Dekko Drive
Garrett, IN 46738
Ship to: Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





From: John McKee <jmmckee@xxxxxxxxxxxxxx>
To: Midrange Systems Technical Discussion
<midrange-l@xxxxxxxxxxxx>,
Date: 10/04/2012 09:42 AM
Subject: The i and DHCP
Sent by: midrange-l-bounces@xxxxxxxxxxxx



I haven't checked the countdown clock this morning. Probably 28 days
left. So, this isn't critical.

Corporate mandated switching from static addressing to DHCP. We get
random calls where a 5250 session cannot sign on or just quits
working. The corporate help desk has decided that if they receive
two
such calls, then the i just HAS to be down - despite the fact that we
have several hundred attached and functioning workstations.

Anyway, here is my question: If a DHCP connection is established
with
the i, and then the lease on the workstation IP address expires, and
a
different IP address is subsequently assigned to the workstation
(sorry for the wordiness). is there any way that the i can determine
that address for that session has changed and do something about it?

I know the device description has the IP in it when a connection is
established. But, what happens when that address changes?


BTW, when corporate office sends out a bogus "system down" task, they
are done - task has been assigned. We get the heat for taking "too
long" to resolve the issue.

John McKee
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