Jump to content


Register a free account to unlock additional features at BleepingComputer.com
Welcome to BleepingComputer, a free community where people like yourself come together to discuss and learn how to use their computers. Using the site is easy and fun. As a guest, you can browse and view the various discussions in the forums, but can not create a new topic or reply to an existing one unless you are logged in. Other benefits of registering an account are subscribing to topics and forums, creating a blog, and having no ads shown anywhere on the site.

Click here to Register a free account now! or read our Welcome Guide to learn how to use this site.


DHCP serving wrong Gateway address (due to reservation?)

  • Please log in to reply
1 reply to this topic

#1 bmeGT


  • Members
  • 1 posts
  • Local time:05:44 PM

Posted 20 September 2016 - 10:47 AM



We have two DCs servers on campus handling DHCP. Both are running Server 2008 R2.


  • DC-1 (physical) – scope that takes care of all clients with the exclusions of 10.1.46 and 10.1.47 IP addresses. Serves a gateway address of our firewall on campus ( The clients that are on our internal campus VLAN network (our primary network) look to this DC first.


  • DC-2 (virtual) - scope that takes care of all clients with a 10.1.46-10.1.47 address. It is set to deny anyone else. Serves a gateway address of a different firewall on campus. The clients that are on a different internal campus VLAN network look to this DC first.


For all intents and purposes, the clients that pull DHCP from DC-1 should not care about DC-2 in anyway shape or form. DC-2 should be ignoring anything that is not a 10.1.46 or 10.1.47 device.




Lately all clients that are on our internal campus VLAN (that should look to DC-1 for an address) have been receiving a gateway from DC-2. Since the gateway that is being served from DC-2 is configured to allow only 10.1.46 and 10.1.47 traffic (as it should), none of our clients are able to get on the internet. A simple release renew fixes the problem. We have over 1000 devices on primary internal campus VLAN.


My question is why are our clients being served the wrong gateway address?


It is also important to note that the only clients that are having these issues are clients that have recently gone through a DHCP reservation change (10.1.2.x have been changed to 10.1.6.x, 10.1.3.x have been changed to 10.1.7.x and 10.1.4.x have been changed to 10.1.8.x). This results in about 300 devices campus wide. The existing reservations that were changed had been in place since 2013.


Any advice or ideas as to why a reservation change could cause this? Or is that just a simple coincidence?


TIA and please let me know if there is any further info you need from me. 




-------EDITS BELOW THIS LINE---------


The DHCP server which serves 90% of campus (DC-1) has the correct DNS and Router entries under the server options configuration tab.

The DHCP server which serves 10% of campus (DC-2) has the correct DNS and Router entries under the server options configuration tab.

Edited by bmeGT, 20 September 2016 - 10:58 AM.

BC AdBot (Login to Remove)


#2 memphizen


  • Members
  • 6 posts
  • Local time:04:44 PM

Posted 03 October 2016 - 03:46 PM

What was your process was for changing those reservations?  Sounds like they pulled down the incorrect gateway address during the process.  Release/renew fixing it makes me think they pulled incorrect info from somewhere/something else.  I've seen this happen when for example a newly installed device on the network had a DHCP server built in and enabled by default (but wasn't intended to handle DHCP,) leading to incorrect IP info being pulled. 

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users