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Home > Archive > Unix administration > January 2004 > static / dymamic IP interplay - DHCP question, ntwk 101
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static / dymamic IP interplay - DHCP question, ntwk 101
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| There are two PCs on a win2k network, PCs and PCd.
PCs has a static ip. PCd uses DHCP.
Say PCd has obtained IP address 101, then someone cuts the network cable.
In otherwords, PCd leaves the network in some irregular fashion.
Now PCs fires up. Its static address is 101. What will happen?
Will it run into the "lease" or will it enjoy the resources of the
network? How long, if at all, will this address be unavailable?
Thanks
PS - previous response to this in other another group resulted in
'why are you doing this' and so on. This is a question about how
DHCP works. I want to understand the process. Yes, this
is a w2k network, but don't unix and windows implement most tcp/ip
utilities the same? (have two years of unix as a user and light
c programmer)
Thanks again.
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| Davide Bianchi 2004-01-23, 5:11 pm |
| woof <drubnone@yahoo.com> wrote:quote:
> Say PCd has obtained IP address 101
> Now PCs fires up. Its static address is 101.
If you have a machine with static IP that his also in the same
dhcp pool it's an error. If PCs has IP 101, that IP should be
outside the IP pool of the DHCP server.
quote:
> Will it run into the "lease"
No it wont. If the DHCP server si half-smart it will expire the
lease of the 'dead' machine, but the IP will be signed as 'free'
and it could be re-assigned to another machine, but when that will
happen the machine will complain about the fact that the IP is
alredy in use.
quote:
> 'why are you doing this' and so on. This is a question about how
> DHCP works. I want to understand the process.
Then read the documentation of DHCP.
quote:
> but don't unix and windows implement most tcp/ip
> utilities the same?
Yah! Sure! Like hell!
Davide
--
| Life is like sendmail: you're not sure you know how to handle it, but
| you know it'll end in tears. -- Malcolm Ray
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| In article <bt6nq6$3sbsp$1@ID-18487.news.uni-berlin.de>, Davide Bianchi wrote:quote:
> woof <drubnone@yahoo.com> wrote:
>
> If you have a machine with static IP that his also in the same
> dhcp pool it's an error. If PCs has IP 101, that IP should be
> outside the IP pool of the DHCP server.
Indeed.
quote:
>
> No it wont. If the DHCP server si half-smart it will expire the
> lease of the 'dead' machine, but the IP will be signed as 'free'
> and it could be re-assigned to another machine, but when that will
> happen the machine will complain about the fact that the IP is
> alredy in use.
Some dhcpds mark the ip as ``abandoned'' and then refuse to touch it.
At least isc-dhcpd 3 (don't know about 2, never dealt with it) can.
This has the side-effect of certain releases of winxx slowly making
the dhcpd abandon the entire pool because they already answer a ping
to the address they expect to get from the dhcpd before it is assigned.
For that reason you can turn the behaviour of ping-first off.
--
j p d (at) d s b (dot) t u d e l f t (dot) n l .
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| I assume, given your "like hell", this description of DHCP
is the unix implimentation? If not, what document would I
read that applies to Windows stuff. Is there one document that
discusses the difference between the two ports? Do "smart"
DHCPs exists in only unix, or both? What's is smart? If
static machine shows up, does DHCP go and ping the previous
lease owner?
Thanks like hell. :-)
Davide Bianchi <davideyeahsure@onlyforfun.net> wrote in message news:<bt6nq6$3sbsp$1@ID-18487.news.uni-berlin.de>...quote:
> woof <drubnone@yahoo.com> wrote:
>
> If you have a machine with static IP that his also in the same
> dhcp pool it's an error. If PCs has IP 101, that IP should be
> outside the IP pool of the DHCP server.
>
>
> No it wont. If the DHCP server si half-smart it will expire the
> lease of the 'dead' machine, but the IP will be signed as 'free'
> and it could be re-assigned to another machine, but when that will
> happen the machine will complain about the fact that the IP is
> alredy in use.
>
>
> Then read the documentation of DHCP.
>
>
> Yah! Sure! Like hell!
>
> Davide
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| Davide Bianchi 2004-01-23, 5:11 pm |
| woof <drubnone@yahoo.com> wrote:quote:
> I assume, given your "like hell", this description of DHCP
> is the unix implimentation?
DHCP is described by some well-know RFC, of course, since
Microsoft can't implement a protocol 'as is', they have their
own quirks.
quote:
> read that applies to Windows stuff.
Why should they document something for someone else? Hell! They
haven't yet documented how their crappy disk sharing works after
ten years they started with it. And they have based _everything_
on that crap! Not to speak about other 'interesting' things like
the format of their word processor documents file...
quote:
> static machine shows up, does DHCP go and ping the previous
> lease owner?
It depends by the client and the server. If the server is dumb
and send an IP that is in use but the client is smart enough to
check it will refuse the IP and ask for another. On the other
end, if the server is smart enough and check _before_ handing
out the IP the client can be dumb. Dumb client are likely to be
found in very dumb or memory-restricted devices (handheld and
the like), while smart servers are likely to be found in Unixworld.
AFAIK Microsoft is quite dumb in both side. The server won't give
a damn and if the client can't get the IP he wants he will assume
a generic IP that won't connect to anything, so you ends up with a
non-networked machine... veeeeery clever Redmond...
Davide
--
| The relative speed of a computer, regardless of CPU architecture, is
| inversely proportional to the number of Microsoft products installed.
| -- From a Slashdot.org post
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