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Why do all my IP's on the network resolve to AMontpellier-257-1-113-2.w90-0.abo.wanadoo.fr

Posted on 2008-10-29
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Last Modified: 2010-04-21
I have a network with over 100 users. All IP's, except my firewall, on the network resolve to AMontpellier-257-1-113-2.w90-0.abo.wanadoo.fr, an ISP in Montpellier, France. I am in Canada and have no association with Wanadoo. This issue has been going on longer than I have been at this company and so I have no idea how it started. I have checked my DNS server for any entries to Wanadoo and found nothing. All DNS entries seem fine.

I dont know how specific you need me to be about my setup but I am running three servers, one win2k, and two win2k3. All pcs have computer names and are joined to the domain. When I ping -a any ip I get AMontpellier-257-1-113-2.w90-0.abo.wanadoo.fr as the name, except the firewall which resolves properly.

Please let me know if you need more info than that. Thanks.
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Question by:Plaintree_Systems
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Fred Marshall earned 250 total points
ID: 22832067
That name AMontpellier-257-1-113-2.w90-0.abo.wanadoo.fr  resolves by reverse DNS to 90.0.0.2.

Why do I suspect that somehow you're using *public* IP addresses 90.0.0.xxx inside your LAN?  If so, then any of the LAN addresses reverse DNS to the public hosts.

What is the subnet you're using in the LAN?
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by:BigRat
ID: 22832079
Probably because you are using DHCP with a base IP of 90.0.0.0 which is allocated to wanadoo.fr
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by:Fred Marshall
ID: 22832246
And, this suggests a typo in the DHCP setup where you really meant to use 10.0.0.0 which *is* a private address range.
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Author Closing Comment

by:Plaintree_Systems
ID: 31511210
Thanks for the quick answer.
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Author Comment

by:Plaintree_Systems
ID: 22832279
Yes, that would explain it. It seems the previous IT guy made the mistake.. Anyone know the fastest way to change an entire subnet, including static PC's and printers without manually changing them all?
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by:Fred Marshall
ID: 22832814
Well, if they're static, then they're static - which means manual.
You might consider changing some static addresses to dynamic (DHCP) first.
This may not seem like the "fastest" but in the long run it may be.
I prefer to keep printers static but that's just me.
Routers are generally static.


For all of the hosts on DCHP, I would suggest rebooting them after changing the DHCP server.

Here is what I'd do:

1) plan carefully
.. which static addresses will be changed first / last?
.. when will the DCHP server be changed in the process?
.. are you prepared to wait for the name service to refresh so that My Network Places looks normal?  This can take a long time - so be patient.
..be ready to handle unsuspected "static" configurations that you thought were DHCP.
..look for and plan to change any static *routes* that are in the routers, switches or individual computers.  This is less likely to be present but a big headache if not dealt with!!

["Normally" the only static routes are to things like the identified gateway and this should be dealt with by the DHCP.  However, sometimes there are static routes.  For example, let's say that you have a VPN device that is not also the internet gateway.  Any packets destined for the VPN have to be routed to that device on the LAN.  Either the route will be entered into the routing table on the gateway/router or possibly on any of the client computers themselves:  Command Line: route print
should show you if there are any "persistent routes" which you will want to pay attention to.]

2) implement the plan.  The "big step" will be:
..change the DHCP server settings
..reboot all the hosts so the addresses will renew.  (there may be other ways to do this but under the circumstances this is probably the most direct and reliable).
- reboot all switches, routers, etc.
If you can afford it, just turn off all the client computers, change the DHCP server, reboot the switches and routers and then turn on all the computers.

If you have multiple resources then you might switch a critical few computers to the new subnet first - so you have two address ranges working at the same time.  Then migrate computers one at a time or in bunches to the new range.  The possibilities are endless.
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Author Comment

by:Plaintree_Systems
ID: 22833370
fmarshall: I would like to thank you very much for your help with this. I will follow your advice and plan according. Christmas is coming and we have a planned shutdown, so luck is with us there.

Much appreciated to all.

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