DHCP problem

  • Thread starter Thread starter jojo
  • Start date Start date
J

jojo

Dear all,
In our office has a DHCP server (win2000) and DHCP lease set to never
expired. However, some of users often has a problem with IP
confliction.
1) The users have IP conflict problem ususally are the XP user and
didn't join to our domain. Both machines set to get IP dynmatically.
For example, PC A report have IP confliction and I found that the other
machine(PC B) that conflicted with A through MAC address. I found PC B
also get IP dynmatically. Any reason will make this happen?

2) My DHCP server also have some strange problem, some IP didn't show
in address lease list. I try to run reconile and refresh the list.
However, they didn't show. Until I restart the client's PC.

3) I have a question about the dhcp data file (dhcp.mdb). The modified
date is the time I restart the DHCP server. Is it normal? Will the dhcp
data be modified periodically?

4) Will the XP fire wall blocks the ping from DHCP if the client is
not in the same domain?

5) If I have a NB connects to our network and DHCP assigns an IP to
it. Some reason I turn off and leave the office. Then next time I come
back and connect to our network. Will conflict detection run?

Thank you. Any suggestion will be appreciated.
Thanks

Regards,
Chi
 
Hi Ben,
Yes, we only have 1 DHCP server in our network. We have around 20
workstation and 80 ip in lease pool. We had set the expire not to be
never before( but not sure is it every 10 days). It still had the same
problem.
Like just now, we have IP conflict again. There are 2 PC (A,B). A was
hibrinated with ip 192.168.9.133(I recorded yesterday) and B was turned
off. B is not in our domain. Both PC are set DHCP. When PC B turn on
and connect internet then suddenly has IP conflict. I check it and it
conflicts with A (I guess since User of A turn on the PC). Any ideas?

And I also have another quest. Will the XP firewall affect the
confliction attempt in DHCP server? will the firewall block the ping
when DHCP try confliction attemption?

Thank you very much

Jojo

Ben M. Schorr - MVP ¼g¹D¡G
 
jojo said:
Hi Ben,
Yes, we only have 1 DHCP server in our network. We have around 20
workstation and 80 ip in lease pool. We had set the expire not to be
never before( but not sure is it every 10 days). It still had the same
problem.
Like just now, we have IP conflict again. There are 2 PC (A,B). A was
hibrinated with ip 192.168.9.133(I recorded yesterday) and B was turned
off. B is not in our domain. Both PC are set DHCP. When PC B turn on
and connect internet then suddenly has IP conflict. I check it and it
conflicts with A (I guess since User of A turn on the PC). Any ideas?
Click to expand...

I would suggest to set the lease expire to 8 hours or so. It works very well
here with about 300 leases (+/- 80% domain workstations, 20% non-domain
laptops).
If you set the lease expire too long, a workstation can use its previous IP
without requesting a new one. This is against the rules of DHCP, but it
happens. When the lease is expired, the workstation will always request a
new IP. Therefore: short lease time is better.
And I also have another quest. Will the XP firewall affect the
confliction attempt in DHCP server? will the firewall block the ping
when DHCP try confliction attemption?
Click to expand...

DHCP request come from the workstation itself, so the firewall should not be
the problem (but can be, check the rules to be sure).

About your question concerning the mdb file: all DHCP server settings are
stored in the registry while running. When the service is stopped, it
writes its info into the mdb file. At start, it reads it out.
So if you want to backup your DHCP server settings (reservations, scopes,
etc), export HKLM\Software\Microsoft\DhcpServer.

Hope this helps.
 
Toni Van Remortel said:
About your question concerning the mdb file: all DHCP server settings are
stored in the registry while running. When the service is stopped, it
writes its info into the mdb file. At start, it reads it out.
So if you want to backup your DHCP server settings (reservations, scopes,
etc), export HKLM\Software\Microsoft\DhcpServer.
Click to expand...

Interesting, I didn't realize that.
It will probably work either way since you would stop the DHCP Service
before copying the MDB file somewhere which would cause it to write itself
out to the MDB before you copied it, so it would be "up-to-date". I moved
mine to a new server that way and never lost any data.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed are my own (as annoying as they are), and not those of
my employer or anyone else associated with me.
-----------------------------------------------------
 
Phillip said:
Interesting, I didn't realize that.
It will probably work either way since you would stop the DHCP Service
before copying the MDB file somewhere which would cause it to write itself
out to the MDB before you copied it, so it would be "up-to-date". I moved
mine to a new server that way and never lost any data.
Click to expand...

Microsofts docs say that you should use both registry export/import and file
copy to transfer a DHCP server ...
Good to know there are more options to it :-)
 
Toni Van Remortel said:
Microsofts docs say that you should use both registry export/import and
file
copy to transfer a DHCP server ...
Good to know there are more options to it :-)
Click to expand...

I guess by doing that you have the data stored in two forms and have a
backup method incase one method fails.

--
Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

The views expressed are my own (as annoying as they are), and not those of
my employer or anyone else associated with me.
-----------------------------------------------------
 
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