hi,
some users have IP conflict. Ip address are destrubuited dynamicaly
by DHCP. why these users have this problem in my netwrok. do u think a
virous cause this problem. how can I prevent it.
thank for help.
suad wrote:
> hi,
> some users have IP conflict. Ip address are destrubuited dynamicaly
> by DHCP. why these users have this problem in my netwrok. do u think a
> virous cause this problem. how can I prevent it.
> thank for help.
>
if a users changes his address manually to one, that has been given to someone else by dhcp,
this will also happen.
make sure they don't have admin rights.
or you are running out of addresses, check your dhcp server settings for
free asddresses and leases.
suad wrote:
> hi,
> some users have IP conflict. Ip address are destrubuited dynamicaly
> by DHCP. why these users have this problem in my netwrok. do u think a
> virous cause this problem. how can I prevent it.
> thank for help.
>
No virus has caused this problem. Either the DHCP server is not working
right wherever it's at on the network or some machines are using static
IP(s) in the range of the DHCP IP(s) that can be issued.
Post removed (X-No-Archive: yes)
I dont know if i fully agree with the lease running out while the
machines are turned off
If a lease was to run out while a pc was turned off and then
consequently this lease was given to another computer, the original
computer when it is turned on should be requesting a new lease as it
knows that its lease has run out
Below is a url to dhcp guide
http://www.tcpipguide.com/free/t_DHCPLeasesLeaseLengthPolici esandManagement-3.htm
It is still obviously a good idea to work out a good lease time that
suits your needs but the dhcp server should handle the machines leases
running out while turned off without problems
I would be looking to see that you dont have any pcs or printers or any
other devices with static ip addresses and, if you are still having
problems i would look at your pool of addresses and see if it is big
enough for all your pcs and devices
Also I would check to see that you dont have 2 devices setup for dhcp,
ie if you have a broadband modem/router it would most likely be by
default setup for dhcp.
Spender wrote:
> On 5 Dec 2006 02:21:31 -0800, "suad"
>
> > some users have IP conflict. Ip address are destrubuited dynamicaly
> >by DHCP. why these users have this problem in my netwrok. do u think a
> >virous cause this problem. how can I prevent it.
>
> Virus? Why does everyone think everything is caused by a virus? Most
> computer problems are caused by Microsoft, not viruses. Oh well.
>
> A problem like this can be caused by the IP address lease running out, as
> far as the DHCP server is concerned, while the system that owns the lease
> is turned off. The DHCP server then hands out that IP to another system.
> The first system is then turned on, and bing, bang, boom you have an IP
> address conflict.
>
> Check the DHCP server and extend the length of the IP address lease
> lifetime. Chances are it is too short for your needs. Then do an "ipconfig
> /release" on all systems, followed by an "ipconfig /renew".
I should have said "" I dont know if i agree that the problem would be
caused by the lease running out while the machines are turned off ""
On Dec 6, 2:11 pm, "cmw"
> I dont know if i fully agree with the lease running out while the
> machines are turned off
>
> If a lease was to run out while a pc was turned off and then
> consequently this lease was given to another computer, the original
> computer when it is turned on should be requesting a new lease as it
> knows that its lease has run out
>
> Below is a url to dhcp guide
>
> http://www.tcpipguide.com/free/t_DHCPLeasesLeaseLengthPolici esandMana...
>
> It is still obviously a good idea to work out a good lease time that
> suits your needs but the dhcp server should handle the machines leases
> running out while turned off without problems
>
> I would be looking to see that you dont have any pcs or printers or any
> other devices with static ip addresses and, if you are still having
> problems i would look at your pool of addresses and see if it is big
> enough for all your pcs and devices
>
> Also I would check to see that you dont have 2 devices setup for dhcp,
> ie if you have a broadband modem/router it would most likely be by
> default setup for dhcp.
>
>
>
> Spender wrote:
> > On 5 Dec 2006 02:21:31 -0800, "suad"
>
> > > some users have IP conflict. Ip address are destrubuited dynamicaly
> > >by DHCP. why these users have this problem in my netwrok. do u think a
> > >virous cause this problem. how can I prevent it.
>
> > Virus? Why does everyone think everything is caused by a virus? Most
> > computer problems are caused by Microsoft, not viruses. Oh well.
>
> > A problem like this can be caused by the IP address lease running out, as
> > far as the DHCP server is concerned, while the system that owns the lease
> > is turned off. The DHCP server then hands out that IP to another system.
> > The first system is then turned on, and bing, bang, boom you have an IP
> > address conflict.
>
> > Check the DHCP server and extend the length of the IP address lease
> > lifetime. Chances are it is too short for your needs. Then do an "ipconfig
> > /release" on all systems, followed by an "ipconfig /renew".- Hide quoted text -- Show quoted text -
Post removed (X-No-Archive: yes)
Spender
> On 5 Dec 2006 02:21:31 -0800, "suad"
>
>> some users have IP conflict. Ip address are destrubuited dynamicaly
>>by DHCP. why these users have this problem in my netwrok. do u think a
>>virous cause this problem. how can I prevent it.
>
> A problem like this can be caused by the IP address lease running out, as
> far as the DHCP server is concerned, while the system that owns the lease
> is turned off. The DHCP server then hands out that IP to another system.
> The first system is then turned on, and bing, bang, boom you have an IP
> address conflict.
>
No, that should not cause any problems: if a device with an expired lease
is switched on, it does a DHCPREQUEST for its old IP, but the DHCP server
rejects if the IP has already been granted to another device. If the IP
address has not been given to another device, it'll deliver a DHCPACK.
I've seen several causes for this problem:
1. a PC with 'internet sharing' switched on will act as a DHCP server
2. I've seen (very long ago) a switch (Cisco IIRC) to assign IP addresses
to its own ports when given by a DHCP server
3. The pool is too small
4. like already suggested: someone is fiddling with fixed IP addresses
Peter
--
http://www.boosten.org
Mail: peter at boosten dot org
In article <1165374705.291574.32470@j44g2000cwa.googlegroups.com>,
mailcmw@gmail.com says...
> I dont know if i fully agree with the lease running out while the
> machines are turned off
>
> If a lease was to run out while a pc was turned off and then
> consequently this lease was given to another computer, the original
> computer when it is turned on should be requesting a new lease as it
> knows that its lease has run out
>
> Below is a url to dhcp guide
>
> http://www.tcpipguide.com/free/t_DHCPLeasesLeaseLengthPolici esandManagement-3.htm
>
> It is still obviously a good idea to work out a good lease time that
> suits your needs but the dhcp server should handle the machines leases
> running out while turned off without problems
>
> I would be looking to see that you dont have any pcs or printers or any
> other devices with static ip addresses and, if you are still having
> problems i would look at your pool of addresses and see if it is big
> enough for all your pcs and devices
>
> Also I would check to see that you dont have 2 devices setup for dhcp,
> ie if you have a broadband modem/router it would most likely be by
> default setup for dhcp.
There can be weird issues with Windows and DHCP.
I work from home, and use a software VPN to connect to work. At night, I
turn off the computer and the router (Linksys BEFSX41, the VPN on it is
no longer used) and the modem (Motorola 5120). The router is set up with
standard DHCP, using 192.168.3.xxx. The usual .1.xxx and .2.xxx
addresses are set up for my backup DSL connection which has it's own
modem and router (an identical Linksys BEFX41, but configured
differently due to issues trying to communicate with the Siemens 4100
DSL modem). I don't use both simultaneously, but wanted to keep the
routers separate.
For weeks, I had issues where the computer (running Win2K) would sit at
'Preparing Network connections' for as long as 2-3 minutes. I originally
though this was due to it being part of a corporate domain and trying to
look for something.
Also, every once in awhile, my VPN would drop and pop up the VPN login.
A clue came when I looked at the VPN log, and saw a note that it had
dropped because the IP address had changed to 0.0.0.0. I also realized
that this once happened exactly 24 hours after having turned on the
computer at an odd time one day. The router is set to a standard 24 hour
lease.
I changed the computer to use a fixed IP (outside the DHCP range), and
all my problems disappeared. It boots up fast and hasn't dropped the
VPN.
--
If there is a no_junk in my address, please REMOVE it before replying!
All junk mail senders will be prosecuted to the fullest extent of the
law!!
http://home.att.net/~andyross
I agree fully with what you have said, just one more point i would like
to add,
I have seen this problem on a few occasions in a company that I
previously worked for.
It happened at 2 different sites, we were getting ip conflicts with
just 2 machines.
One of the problems was with a laptop and everytime it connected at a
particular site it would give an ip conflict with another pc.
I traced the problem to this laptops network card having the same MAC
address as one of the PC's network cards.
I know that every network card should have a unique MAC address but it
happened a couple of different times at this company and each time it
was the fact that the MAC address on 2 different NICs was the same.
I haven't seen this problem since though so I guess its fairly rare.
Peter Boosten wrote:
> Spender
> > On 5 Dec 2006 02:21:31 -0800, "suad"
> >
> >> some users have IP conflict. Ip address are destrubuited dynamicaly
> >>by DHCP. why these users have this problem in my netwrok. do u think a
> >>virous cause this problem. how can I prevent it.
> >
> > A problem like this can be caused by the IP address lease running out, as
> > far as the DHCP server is concerned, while the system that owns the lease
> > is turned off. The DHCP server then hands out that IP to another system.
> > The first system is then turned on, and bing, bang, boom you have an IP
> > address conflict.
> >
>
> No, that should not cause any problems: if a device with an expired lease
> is switched on, it does a DHCPREQUEST for its old IP, but the DHCP server
> rejects if the IP has already been granted to another device. If the IP
> address has not been given to another device, it'll deliver a DHCPACK.
>
> I've seen several causes for this problem:
> 1. a PC with 'internet sharing' switched on will act as a DHCP server
> 2. I've seen (very long ago) a switch (Cisco IIRC) to assign IP addresses
> to its own ports when given by a DHCP server
> 3. The pool is too small
> 4. like already suggested: someone is fiddling with fixed IP addresses
>
> Peter
>
> --
> http://www.boosten.org
>
> Mail: peter at boosten dot org
Post removed (X-No-Archive: yes)
"cmw"
news:1165547641.831582.255840@f1g2000cwa.googlegroups.com...
>
> One of the problems was with a laptop and everytime it connected at a
> particular site it would give an ip conflict with another pc.
>
> I traced the problem to this laptops network card having the same MAC
> address as one of the PC's network cards.
>
> I know that every network card should have a unique MAC address but it
> happened a couple of different times at this company and each time it
> was the fact that the MAC address on 2 different NICs was the same.
>
> I haven't seen this problem since though so I guess its fairly rare.
>
Are you sure that this conflict was not due to either party using software
to spoof the MAC address?
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