Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win

x
?
Solved

DHCP failover not working

Posted on 2016-09-19
13
Medium Priority
?
328 Views
Last Modified: 2016-10-19
I have to 2012 R2 server configured for DHCP Failover, and it was working fine.  Lately they haven't been communicating with each other.  If I set an IP address through the DHCP server only one sees it and the other just ignores it.  This leads to some confusion between the servers.  They are both Domain Controllers and DNS configured on both.  How can I force them to communicate with each other.  I tried doing the replicate failover scope option in the DHCP  and it works for the secondary one but the primary one tells me that they are already in sync.  
How do I get them to work together again?
0
Comment
Question by:lcfrederickson
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 7
  • 6
13 Comments
 
LVL 59

Expert Comment

by:Cliff Galiher
ID: 41805660
"If I set an IP address through the DHCP server "

Failover *only* syncs leases. It does not, and never has, done automatic syncing of reservations or scope options. Those must be set per server.
0
 

Author Comment

by:lcfrederickson
ID: 41805737
The way I had it set up both DHCP servers shared the same scope and addresses.  When one went down the other would take over the full load.  It was working fine until the became disconnected somehow and aren't communicating anymore.
0
 
LVL 59

Expert Comment

by:Cliff Galiher
ID: 41805746
Scope? Yes.
Scope OPTIONS? No.

Address leases? Yes.
Reserved addresses? No.

DHCO failover in 2012/R2 *never* supported syncing the things I listed above. So if you think you remember it doing so, you are misremembering.
0
Veeam Disaster Recovery in Microsoft Azure

Veeam PN for Microsoft Azure is a FREE solution designed to simplify and automate the setup of a DR site in Microsoft Azure using lightweight software-defined networking. It reduces the complexity of VPN deployments and is designed for businesses of ALL sizes.

 
LVL 59

Expert Comment

by:Cliff Galiher
ID: 41805752
Official technet page:

https://technet.microsoft.com/en-us/library/dn338983(v=ws.11).aspx

Note the "important" box:

"If changes are made to a failover-enabled scope, you must manually replicate these changes to the partner server in order to synchronize scopes on both DHCP servers."

Changes must be MANUALLY replicated. Automatic replication of reservations and scope options DOES NOT OCCUR. This is official Microsoft documentation.
0
 

Author Comment

by:lcfrederickson
ID: 41805762
OK so I set up both server with the same scope but as I added reservations they couldn't  communicate that?  If I have reservations am I better off not using the failover?  It sounded really good and like I said it seems to work for awhile.  The reservations were seen in both servers.
0
 

Author Comment

by:lcfrederickson
ID: 41805764
What does the replicate failover scopes do?  Not sure I understand
0
 
LVL 59

Expert Comment

by:Cliff Galiher
ID: 41805773
A failover scope will share lease information. But scope options and reservations are not automatically replicated. Not sure how else to repeat that. What specific question do you have?
0
 

Author Comment

by:lcfrederickson
ID: 41805785
I'm not trying to be a problem but I did ask 2 specific questions.  If I use reservations am I better off not using using the DHCP Failover?  Number 2, what does the replicate failover scopes options do if the scopes won't replicate?   I did set up the scopes on each server but if they can't share the reservations then do I just not do reservations?  That would be pretty difficult.
0
 
LVL 59

Expert Comment

by:Cliff Galiher
ID: 41805787
If you *only* use reservations, DHCP failover may be of limited value. That depends on if you also use standard dynamic leases.

Replicate failover scopes does a one-time point A to point B copy of settings. It doesn't combine them. It doesn't copy from point B back to point A. It does no conflict avoidance or resolution. It is a manual replication point in time.
0
 

Author Comment

by:lcfrederickson
ID: 41805789
The vast majority of addresses and standard dynamic.  Most of the reservations are for NAS Backups and computers that I want to let through our SonicWall firewall.  If I can't use the reservations do I need to have 2 DHCP servers for the DHCP Failover and another one to do the reservations?  I'm not trying to be a pain, I just don't understand if I can't use reservations on the DHCP Failover servers what is the solution?
0
 

Author Comment

by:lcfrederickson
ID: 41805790
Would I be better off just keeping a backup of the reservations and a backup DHCP ready in put them in in case of a failure of the DHCP server?  That would mean down time.
0
 
LVL 59

Accepted Solution

by:
Cliff Galiher earned 2000 total points
ID: 41805796
You can certainly use DHCP failover. And if you use standard dynamic leases, it is probably worth it to do so. As to your reservations, you just have to get in the habit of making changes on both servers or always using one server to make edits as a "master" server and then forcing a manual replication whenever you make changes. It is a workflow issue,  not a technical one.
0
 

Author Comment

by:lcfrederickson
ID: 41807341
Thanks!  Learned alot!
0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Resolve DNS query failed errors for Exchange
A procedure for exporting installed hotfix details of remote computers using powershell
In this Micro Tutorial viewers will learn how to restore their server from Bare Metal Backup image created with Windows Server Backup feature. As an example Windows 2012R2 is used.
This tutorial will walk an individual through the steps necessary to join and promote the first Windows Server 2012 domain controller into an Active Directory environment running on Windows Server 2008. Determine the location of the FSMO roles by lo…

636 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question