IP Address conflict - same address as server

I've no idea where to post this, there seems to be no plain vanilla
networking forum, so bear with me.

Someone, presumably with a laptop, plugged it into our network today.  It
appears it had a manually set IP address that was the same as our Groupwise
server.  

Everyone's GW client or WebAccess Connection immediately exited, presumably
because they were suddenly talking to the wrong computer.

I found the TCPIP error messages on the server console when I went to see
what the hell happened.

NW65SP7 

I've got the MAC address and I'll try and track it down.
Any ideas how to stop this sort of thing happening, it resolved almost at
once - or seems to have.  I was able to get back in about 30 seconds later
without a problem.

TIA

 
-- 

Geoff Roberts
Computer Systems Manager
Saint Mark's College
Port Pirie, South Australia
geoffrobxATstmarksxdotppxdotcatholicxdoteduxdotaux
Remove the x's

0
Geoff
2/20/2008 12:19:50 AM
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Hi,

Geoff Roberts wrote:
> Any ideas how to stop this sort of thing happening, 

Outright impossible. 

CU,
-- 
Massimo Rosen
Novell Product Support Forum Sysop
No emails please!
http://www.cfc-it.de
0
Massimo
2/20/2008 12:30:15 AM
>>> On Wednesday, 20 February 2008 at 11:00 am, in message
<47BB7488.EE4FA75E@spamcfc-it.de>, Massimo Rosen<mrosenno@spamcfc-it.de>
wrote:
> Hi,
> 
> Geoff Roberts wrote:
>> Any ideas how to stop this sort of thing happening, 
> 
> Outright impossible. 

Yeah, figured that might be the case.  I certainly couldn't think 
of anything.   

Nice to have it confirmed by a higher intelligence.

Thanks for responding so fast.

cheers


-- 

Geoff Roberts
Computer Systems Manager
Saint Mark's College
Port Pirie, South Australia
geoffrobxATstmarksxdotppxdotcatholicxdoteduxdotaux
Remove the x's

0
Geoff
2/20/2008 5:51:35 AM
If you can disable the ports that aren't normally in use, that would lower 
how often this kind of thing would happen, but you can't eliminate it.

"Geoff Roberts" <geoffrobx@stmarksx.ppx.catholicx.edux.aux> wrote in message 
news:47BC538C.A099.0007.0@stmarksx.ppx.catholicx.edux.aux...
>>>> On Wednesday, 20 February 2008 at 11:00 am, in message
> <47BB7488.EE4FA75E@spamcfc-it.de>, Massimo Rosen<mrosenno@spamcfc-it.de>
> wrote:
>> Hi,
>>
>> Geoff Roberts wrote:
>>> Any ideas how to stop this sort of thing happening,
>>
>> Outright impossible.
>
> Yeah, figured that might be the case.  I certainly couldn't think
> of anything.
>
> Nice to have it confirmed by a higher intelligence.
>
> Thanks for responding so fast.
>
> cheers
>
>
> -- 
>
> Geoff Roberts
> Computer Systems Manager
> Saint Mark's College
> Port Pirie, South Australia
> geoffrobxATstmarksxdotppxdotcatholicxdoteduxdotaux
> Remove the x's
> 


0
Bruce
2/20/2008 12:56:43 PM
A bit extreme, and I'm not 100% sure how to configure it, but if you have a 
2nd NIC on the server, or it's plugged to a level 2 switch, you could create 
a separate LAN segment for the users, and reserve the main one for your 
server equipment.

Example:
- Primary server address is 172.16.10.xxx
- Create another LAN segment 172.16.12.xxx
- Arrange your network so that the users are only plugged into the 
172.16.12.xxx switch / NIC / whatever, and getting DHCP addresses on that 
segment only (no DHCP on the 172.16.10.xxx segment)
- Add routing to allow the 2 to communicate

Unless I'm mistaken, if then one of your users has a static address in the 
172.16.10.xxx range, that they won't be able to communicate at all with 
anybody on the 172.16.12.xxx LAN and vice versa, so they can't interfere 
even if they do have that conflicting address.  I haven't tried this so it's 
worth a test if you're considering it seriously.

Again a bit extreme, but it would effectively lock out user machines from 
interfering with your server addresses.

Ciao
James

"Geoff Roberts" <geoffrobx@stmarksx.ppx.catholicx.edux.aux> wrote in message 
news:47BC05CC.A099.0007.0@stmarksx.ppx.catholicx.edux.aux...
> I've no idea where to post this, there seems to be no plain vanilla
> networking forum, so bear with me.
>
> Someone, presumably with a laptop, plugged it into our network today.  It
> appears it had a manually set IP address that was the same as our 
> Groupwise
> server.
>
> Everyone's GW client or WebAccess Connection immediately exited, 
> presumably
> because they were suddenly talking to the wrong computer.
>
> I found the TCPIP error messages on the server console when I went to see
> what the hell happened.
>
> NW65SP7
>
> I've got the MAC address and I'll try and track it down.
> Any ideas how to stop this sort of thing happening, it resolved almost at
> once - or seems to have.  I was able to get back in about 30 seconds later
> without a problem.
>
> TIA
>
>
> -- 
>
> Geoff Roberts
> Computer Systems Manager
> Saint Mark's College
> Port Pirie, South Australia
> geoffrobxATstmarksxdotppxdotcatholicxdoteduxdotaux
> Remove the x's
> 


0
JJB
2/20/2008 4:35:15 PM
Hi,

JJB wrote:
> 
> A bit extreme, and I'm not 100% sure how to configure it, but if you have a
> 2nd NIC on the server, or it's plugged to a level 2 switch, you could create
> a separate LAN segment for the users, and reserve the main one for your
> server equipment.
> 
> Example:
> - Primary server address is 172.16.10.xxx
> - Create another LAN segment 172.16.12.xxx
> - Arrange your network so that the users are only plugged into the
> 172.16.12.xxx switch / NIC / whatever, and getting DHCP addresses on that
> segment only (no DHCP on the 172.16.10.xxx segment)
> - Add routing to allow the 2 to communicate

ice idea, until then someone comes up with the same static IP as the
router. That's not less likely in any way, and the effect will be as
desastrous. ;-)
 
CU,
-- 
Massimo Rosen
Novell Product Support Forum Sysop
No emails please!
http://www.cfc-it.de
0
Massimo
2/20/2008 9:18:47 PM
True... I have a "USERS TAMER" inflatable hammer in my office for such 
occasions...  ;-)

But depending on the complexity or number of servers or your goals, it would 
still be nice to segregate the user LAN away from the servers LAN, so that 
at the very least the servers don't lose their IP, this way they can 
continue to talk to each other, or (for instance) GWIA can continue to 
operate, or the servers can continue to interact with remote offices on a 
WAN, etc...

Cheers
James

"Massimo Rosen" <mrosenno@spamcfc-it.de> wrote in message 
news:47BC9929.6EC3D917@spamcfc-it.de...
> Hi,
>
> JJB wrote:
>>
>> A bit extreme, and I'm not 100% sure how to configure it, but if you have 
>> a
>> 2nd NIC on the server, or it's plugged to a level 2 switch, you could 
>> create
>> a separate LAN segment for the users, and reserve the main one for your
>> server equipment.
>>
>> Example:
>> - Primary server address is 172.16.10.xxx
>> - Create another LAN segment 172.16.12.xxx
>> - Arrange your network so that the users are only plugged into the
>> 172.16.12.xxx switch / NIC / whatever, and getting DHCP addresses on that
>> segment only (no DHCP on the 172.16.10.xxx segment)
>> - Add routing to allow the 2 to communicate
>
> ice idea, until then someone comes up with the same static IP as the
> router. That's not less likely in any way, and the effect will be as
> desastrous. ;-)
>
> CU,
> -- 
> Massimo Rosen
> Novell Product Support Forum Sysop
> No emails please!
> http://www.cfc-it.de 


0
JJB
2/20/2008 10:24:05 PM
>>> On Thursday, 21 February 2008 at 8:54 am, in message
<9M1vj.3199$Ec7.3165@kovat.provo.novell.com>,
JJB<103REMOVE-THIS267.1555@compuserve.com> wrote:
> True... I have a "USERS TAMER" inflatable hammer in my office for such 
> occasions...  ;-)

I have something similar.  But it's not inflatable ;^)
 
> But depending on the complexity or number of servers or your goals, it 
> would still be nice to segregate the user LAN away from the servers LAN,
so 
> that at the very least the servers don't lose their IP, this way they can

> continue to talk to each other, or (for instance) GWIA can continue to 
> operate, or the servers can continue to interact with remote offices on 
> a WAN, etc...

Sounds nice, but not sure how to achieve it. 

The servers are in a 10.0.0.x address range on the 'inside' network.
They also have an 'outside' NIC that is in the 30.0.0.x range that is NAT to
the 
real internet IP address (except for the OES1/Linux server, NAT doesn't play
well
on that for some reason so it has the real IP bound to the outside NIC.

Yes, this makes for some interesting configuration issues but it seems to
work pretty well now.

Each area or room is in a 10.0.x.x range ie printers are 10.0.1.x, Room7 is
10.0.7.x
and so on. Fixed IP addresses are provided by Novell DHCP by MAC address.
(some printers
are hard coded, and a couple of workstations that temporarily require direct
gateway access.
Since our gateway blocks ALL internet traffic to anything not in the
10.0.0.x subnet, all other
ip addresses are forced to use the proxy server at 10.0.0.7 which requires
them to pass through
the ContentKeeper bridge, which authenticates them to eDirectory for
filtering and tracking.
We also have a 'nointernet' Group in eDirectory so that, ahem, naughty boys,
can be locked out of
the internet without denying them access to the files on the server and
intranet.

We currently use a 255.0.0.0 mask so everything can see everything and there
are no routers.

There is a 'generic' 10.0.20.x dynamically assigned subnet for anything that
hasn't got a fixed
IP.  Wireless is assigned by the main DHCP server as well, by MAC address in
a couple of subnets
in the 10.0.51-53 range depending on whether they are staff or student etc.

Hardwired laptops get similar treatment in a subnet in the 41-43 range.

So there are no DHCP addresses being applied in the 10.0.0. subnet and
certainly not 10.0.0.2 which is
not managed by DHCP at all.  Dynamic addresses ONLY come from the 10.0.20.x
subnet range, all others are
fixed by MAC address.

As Massimo suggests, probably not going to help, it only moves the problem
around a little, and I don't have
a router anyway.  The only solution I can think of is to change the server
IP addresses to something a little less likely to come out of a home DSL
boxes DHCP server.
If it becomes a serious issue I'll consider changing them to something in a
10.0.99.x subnet instead.

I'm guessing a bit here, but I suspect that what actually happens is that
the laptop is
in use at home, probably on Bigpond whose in home router/modems use the
10.0.0.x IP address range with the 
modem being 10.0.0.138, so pcs connected to it and it's embedded DHCP server
would get IP addresses starting
with 10.0.0.1 etc, so 10.0.0.2 for someone's laptop is probably quite
likely.

Then they bring it to school and the machine pops up, possibly from standby
*still on the assigned IP from the home DHCP server*
It then asks our DHCP server for it to be renewed.  Our DHCP server
naturally says no and assigns it a new IP from the dynamic subnet.
The IP changes and the conflict disappears almost as soon as it occurs. 
Seconds at most.
I'm not heavily clued on how exactly how DHCP server/client works to that
level so this may or may not
be quite the case, but given that it vanishes almost as soon as it appears,
I think it may be something like that.

Thanks to all.
-- 

Geoff Roberts
Computer Systems Manager
Saint Mark's College
Port Pirie, South Australia
geoffrobxATstmarksxdotppxdotcatholicxdoteduxdotaux
Remove the x's

0
Geoff
2/20/2008 11:14:07 PM
Reply:

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