Right now I have two DHCP servers on one subnet mask. A client can only get an IP address from either server if they have a reservation on that server (based on their MAC). The odd thing that I'm seeing is, let's say user 1 gets an IP address, gateway, dns and dns suffix from server 1 because they have a ip address reservation on that server. A few hours later, that same user's dns suffix will change from the suffix that server 1 assigns them to the suffix that server 2 usually assigns. If I do a simple ipconfig /renew, the network info is renewed and the dns suffix changes back to the suffix that server 1 is supposed to assign. Why is this happening? The user only has a reservation on server 1 but for some reason their dns suffix keeps changing to server 2 information.
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2 DHCP Servers on same network
- Thread starter EST7745
- Start date
Why are you using two DHCP servers for a single subnet? I would recommend reducing to one server, or if you need different pc's to use different gateways, etc. I would suggest creating a VLAN and putting the second DHCP server on the second VLAN along with the pc's that need to use it.
- Thread starter
- #3
You should only have a single DHCP server if you're in an unrouted network with a single subnet. When you're ready to segregate the machines onto different subnets, you can create the DHCP pool for the second subnet then.
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WhoKilledKenny
MIS
The reson it is happening is that a reservation reserves only the IP portion to Mac and not the scope options.
It is ok to have two DHCP servers on one subnet for redundancy, I believe Micosoft recommends an 80/20 split.
What scope option are you using for DNS suffix? 015 DNS Domain Name? From what you described it looks like you are trying to define the suffix based on which DHCP server the client get its reservation. If the scope option is 015 DNS Domain Name, you would not be able to accomplish this, as you can only define one entry for entire network.
It is ok to have two DHCP servers on one subnet for redundancy, I believe Micosoft recommends an 80/20 split.
What scope option are you using for DNS suffix? 015 DNS Domain Name? From what you described it looks like you are trying to define the suffix based on which DHCP server the client get its reservation. If the scope option is 015 DNS Domain Name, you would not be able to accomplish this, as you can only define one entry for entire network.
- Thread starter
- #6
WhoKilledKenny
MIS
Here is how I would set it up. (Two DHCP servers on One subnet).
For Example:
Take the scope as a whole - Say 10.0.1.1 thru 10.0.1.254 with a subnet of 255.255.255.0. Create one scope on each server for this subnet.
Then I would exclude the following addresses on each DHCP server. 10.0.1.1 - 10.0.1.24 (for network resources). 10.0.1.25 - 10.0.1.74 (for printers and other deivces that are required to use static IP). Then let's say I do a 50/50 scope for redundancy. On DHCP2 I would exclude 10.0.1.75 thru 10.0.1.165 (as these are address that DHCP1 will give out). On DHCP1 I would exlcude 10.0.1.166 thry 10.0.1.254 (as these address are given out by DHCP2.
Address Pool is know set up.....
Now Options.
The only scope option I would set up is "003 Router" as this would be the default gateway for the client and this will be different for new subnet scopes you may create in the future.
Server options would be as follows:
015 DNS Domain Name
044 INS/NBNS Servers - if using a WINS Server
046 WINS/NBT Node Type - if using a WINS Server
In your case set the 015 DNS Domain Name option to Yourdomain.com on both DHCP servers. This way the client will always get the same DNS Domain Name no matter which DHCP server services the request.
For reservations, Create the reservation in the scopes on both DHCP servers. This way if DHCP1 is not available to complete the request, DHCP2 is aware that the clients MAC address is using a reservation. Even if the IP for the reservation is in the exclude list on DHCP2.
Again, The entry for 015 has to be the same on both servers.
Hope that answers your question and help to resolve the issue you are seeing.
For Example:
Take the scope as a whole - Say 10.0.1.1 thru 10.0.1.254 with a subnet of 255.255.255.0. Create one scope on each server for this subnet.
Then I would exclude the following addresses on each DHCP server. 10.0.1.1 - 10.0.1.24 (for network resources). 10.0.1.25 - 10.0.1.74 (for printers and other deivces that are required to use static IP). Then let's say I do a 50/50 scope for redundancy. On DHCP2 I would exclude 10.0.1.75 thru 10.0.1.165 (as these are address that DHCP1 will give out). On DHCP1 I would exlcude 10.0.1.166 thry 10.0.1.254 (as these address are given out by DHCP2.
Address Pool is know set up.....
Now Options.
The only scope option I would set up is "003 Router" as this would be the default gateway for the client and this will be different for new subnet scopes you may create in the future.
Server options would be as follows:
015 DNS Domain Name
044 INS/NBNS Servers - if using a WINS Server
046 WINS/NBT Node Type - if using a WINS Server
In your case set the 015 DNS Domain Name option to Yourdomain.com on both DHCP servers. This way the client will always get the same DNS Domain Name no matter which DHCP server services the request.
For reservations, Create the reservation in the scopes on both DHCP servers. This way if DHCP1 is not available to complete the request, DHCP2 is aware that the clients MAC address is using a reservation. Even if the IP for the reservation is in the exclude list on DHCP2.
Again, The entry for 015 has to be the same on both servers.
Hope that answers your question and help to resolve the issue you are seeing.
WhoKilledKenny
MIS
Also,
Sorry not sure if I am understanding the question... Is it your intention to have two different DNS Domain Names? or are you trying to fix a problem where you want the client to have the same DNS Domain Name, but the second server is giving out the wrong name? If the second DHCP server is giving out the wrong name than changing 015 will resolve the issue.
Sorry not sure if I am understanding the question... Is it your intention to have two different DNS Domain Names? or are you trying to fix a problem where you want the client to have the same DNS Domain Name, but the second server is giving out the wrong name? If the second DHCP server is giving out the wrong name than changing 015 will resolve the issue.
- Thread starter
- #9
My intention is to have two different DNS Domain Names. The clients that have their reservation with DHCP Server 2 will eventually be on a completely separate network and therefore using a different DNS server, router etc etc. But we haven't quite gotten to the point where we have separated the networks yet. I'm beginning to think that maybe I should separate the networks first, and then allow the second DHCP server to assign its own separate dns domain name?
WhoKilledKenny
MIS
With what you are trying to do, that looks like the direction you should take. Are you doing a migration from NT to AD? Is that the reason for the two different DNS Domain names?
- Thread starter
- #11
Actually, we have a company within our company that has been using our network resources for several years. Finally, they have decided to kick them off and make them get their own network, servers etc. I am attempting to help them get set up. Thanks for all the suggestions!
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