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The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol. DHCP allows for computers to be configured automatically to communicate with each other over an IP network without the need for manual setup by a network administrator. The implementation of DHCP relies on a DHCP server to hand out network configuration information to DHCP-capable clients that request an IP address (and other information required or useful in communicating with other devices on an IP network). In addition to an IP address, common configuration information served over DHCP includes a default gateway, subnet mask and DNS sever(s).

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To complete unqualified domain name system (DNS) names that will be used to search and submit DNS queries at the client for resolution, you must have a list of DSN suffixes that can be appended to these DNS names.

For DHCP clients, this can be set by assigning the DNS domain name option (Option 15) and providing a single DNS suffix for the client to append and use in searches.
In some circumstances it is preferable that a DHCP client be configured by using multiple DNS suffixes, supported with the use of DHCP Search Option 119.

I am having difficutlies configure this option on Linux DHCP server.  I get error emssages when set following for Option 119 or other options for 15.
supersede domain-search “example.com example.net”;  (for Option 119).

Would you be able to tell me what the correct sentax for this option?
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The 14th Annual Expert Award Winners
LVL 7
The 14th Annual Expert Award Winners

The results are in! Meet the top members of our 2017 Expert Awards. Congratulations to all who qualified!

Trust between two domains
We have two domains on our network. Domain A and B. There is one way trust between domain A and B. Recently we have experienced network issues on domain B and i had to reconfigure network cards on one of the hosts. I think that threw off trust relationship between both domains. I fixed the network related issues, but now users on Domain B are experiencing authentication issues.  I checked trust settings on Domain B DC, it seems to be down. Could i have reset the trust after i reconfigured the nics? How to reestablish the trust without further issues? Thank you for your advice in advanced.

Follow up question:
Domain B has a DC with class A DHCP scope. When i reconfigured the nic cards, DHCP role went down. Scope is down. Doesn't seem to want to come back up. Any suggestions how to troubleshoot this issue?
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We have a customer who bought out another company and merged.

Right now we have both companies in the same building. they are both on different routers and different IP' ranges.
192.168.16.0 and the other is 192.168.1.0

They both have their own domain controllers.

We are going to be bringing them on all the same network.

The company that was bought out uses a sql database program called Miracle.
all the client workstations have the Miracle executable and it is pointing to the database of the server using the Host name not the IP of the server.

Our question is is it possible to demote the server which is now a DC and add it to the main network at a child server?.

or can we just bring the server to the other network as a DC but turn off DHCP and DNS server?
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Dear Experts

We have DHCP server in the LAN please suggest on the following
1. would like to reserve few IP's to few users and we allow only those IP's to access the internal application web based server, please suggest the best practice considering the security controls for the dhcp,
2. is there a way that even though the wifi network password is known to the users still there should be one more level of authentication or some controls only if that is accepted then only  the users device gets IP assigned
please suggest, thanks.
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All entries from DNS are disappeared. if I add any new DNS entry, it is getting auto disappear after refresh.
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Exchanger services stuck in starting state  ( info store,  transporting services,  etc)
but all this is cause by my corrupt dns on the dc. The exchange server even takes for ever log in. " applying user setting"
This is probably due to connectivity issues to the dc

I need to rebuild/ reconfigure my  dns,  it's corrupt,  is there a way to do this with AD integrated?
DCdiag:  dns,  fix  etc all gives the same errors


   Testing server: domain\DC
      Starting test: Connectivity
         The host
         d66657ce-1b25-425b-94a9-545dc1eca351._msdcs.mydomain.local
         not be resolved to an IP address. Check the DNS server, DHCP, se
         name, etc.
         Got error while checking LDAP and RPC connectivity. Please check
         firewall settings.
         ......................... domain controller failed test Connectivity


note,  this has nothing to do with the firewall  

We also had a physical DC,  moved to  VM but it seems like the Tech never resolved issues on the previous DC,  corrupt entriesi in the sysvol.
Can  these entries be cleared out

I've done a metacleanup on the new DC but it still feels like old entries exist somewhere.  
On dns:  I thoroughly went through all folders and removed entries of the old DC,  even on sites and services and ADSIedit
but when you reload on  any zone,  it bring back the old DC,  host file.
Scavenge is turned on.  

There are some loopback entries under reverse lookup but I can't even …
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Win 2016 domain with 2 x DC, 2 x DNS Servers, 2 x DHCP servers, 500 x clients.

DHCP and DNS are linked by the Active Directory.

There are some machines in DNS that have the same IP which is obviously causing name resolution errors. can anyone suggest how I troubleshoot this?

One thing is I have recently changed a DHCP server to a new name, will DNS need to be told about this change?
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Exchanger services stuck in starting state  ( info store,  transporting services,  etc)
but all this is cause by my corrupt dns on the dc. The exchange server even takes for ever log in. " applying user setting"
This is probably due to connectivity issues to the dc

I need to rebuild/ reconfigure my  dns,  it's corrupt,  is there a way to do this with AD integrated?
DCdiag:  dns,  fix  etc all gives the same errors


   Testing server: domain\DC
      Starting test: Connectivity
         The host
         d66657ce-1b25-425b-94a9-545dc1eca351._msdcs.mydomain.local
         not be resolved to an IP address. Check the DNS server, DHCP, se
         name, etc.
         Got error while checking LDAP and RPC connectivity. Please check
         firewall settings.
         ......................... domain controller failed test Connectivity


note,  this has nothing to do with the firewall  

We also had a physical DC,  moved to  VM but it seems like the Tech never resolved issues on the previous DC,  corrupt entriesi in the sysvol.
Can  these entries be cleared out

I've done a metacleanup on the new DC but it still feels like old entries exist somewhere.  
On dns:  I thoroughly went through all folders and removed entries of the old DC,  even on sites and services and ADSIedit
but when you reload on  any zone,  it bring back the old DC,  host file.
Scavenge is turned on.  

There are some loopback entries under reverse lookup but I can't even …
0
in an Active Directory environment, is there any advantage over using Windows DHCP server over any old DHCP service (let's say setting it up on a Linux box or on a Cisco device for instance)?  is it simply a case of using it because it is there?  or is using it a best practice in a Microsoft AD/DNS environment?  reason i'm asking is, we're planning an AD migration to a centralized domain from what we currently have which is a distributed series of AD environments.  there's some debate on whether DHCP should even be included in the scope of the discussions, let alone how it should be implemented.  AD is being centralized, but as a site IT support person, i'm trying to build an argument in favour of my insisting i still have some local management of DHCP (reservations what not).

i guess i'm asking two questions.  1) is Windows DHCP a no-brainer in a fresh or migrated AD environment, and 2) even though i will (in the end) have only OU Admin level access over my local site, is there a way to still allow me DHCP management at my local site?  question 1 is most important to me as i don't know why the Project Managers are treating this aspect of the project lightly.
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Hi Guys

Environment:
Small environment (40 x VMs, Single building)
Cisco 3750 Series Core switch x 2 (24-port) Stacked

We have one IP Helper Address assigned to our Primary Domain Controller for DHCP purposes.
We have a secondary Domain Controller which I have configured to Load Balance IP addresses (50/50 split) for HA. However, this is not going to work as the Core Switch will only see the single IP Helper Address.

How do I add a secondary IP Helper Address on the Core Switch to include the secondary Domain Controller?

In advance thank you for your support.
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Free Tool: Subnet Calculator
LVL 12
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.

I have an OpenMesh WiFi network attached to an OpenMesh 24port switch.  I have it setup with ATT using their Modem/router to do DHCP.  I  got WOW internet (cable - nice and fast) but when I try to switch to the WOW internet, my network fails.  the devices don't get a new IP address and they fail.  I can plug a laptop into the switch/modem that came with WOW and have configured it to do DHCP and passthrough DNS.  but when I go from their switch to the OpenMesh switch it doesn't work.  lights flash but no one is home.
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Does anyone know why some DHCP entries show blank names?  IP, Lease expiration, MAC address, etc.  Just missing a name.  
Would that be some sort of an appliance/hw that without a hostname assigned?
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Background

My company uses VoIP phones. When I setup the phones (approx 15) I gave each phone a fixed IP address by means of creating a DHCP reservation on our Windows 2008 R2 server.

This has worked fine and each phone had a standard IP address on the system. This allowws me to organise the phones for the purposes of QOS and so on.

The problem

I find today that all the phones (bar one) have the wrong IP address.

Looking at the DHCP it seems that the MAC codes assigned to each reservation have been changed - almost randomly reshuffled !!

Now they all work, using a mixture of the wrong reservation and standard DHCP leases, but why and how has this happened ?

The is no possibility that anyone else has worked on the server and done this by intent or accident.

I have no idea when this happened (as I only found it out due to looking into another issue). How can I look and see when the reservations where changed ?

Is there any way a device can update the MAC code assigned to a reservation for a specific IP ?

Any suggestions would be greatly appreciated,
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Folks, do you know what icons mean on DHCP clients.  Some shows a clock and others some sort of checkmark or strike.

This is for Windows Server 2016
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We have just setup a DHCP server in our domain for the first time but it doesn't seem to be dishing out IP addresses. No idea what went wrong as we followed a similar process in another domain and it worked fine. The only difference was the Server OS version.

The OS im using is Win Server 2016 standard and set up with the following config. Please can you advise what could be going wrong.

I can confirm I can ping the router (core switch) address and both DNS servers. Please advise

dhcp1
dhcp2
dhcp3
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I am setting up a test VMware ESXi 6.5 environment via VMware Workstation.
I configured a ESXi host.
Initial setup for vSwitch0 is set for DHCP and obtains an IP address from my ISP server.

ISP vSwitch0
On my other VMs in VMWare Workstation I have 2 NICs on each machine:  Internal (10.1.1.x) & External (DHCP from ISP).

All my machines can communicate with each other except for this ESXi Host, via the Internal NIC.

I am having problems configuring a 2nd NIC for Internal use only.   Meaning there is no GW needed.  My internal network has no Gateway, because it is just within this private network.

How do I setup a second NIC on the ESXi host, so it can communicate with my internal VMs?

Thanks
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What's the best way to switch to another DNS in DHCP server?  
Lower lease -
Change scope options 006 DNS Servers  - reboot
Sounds right?

Is there a way to do it transparently without a boot?
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In the DHCP scope options 006 DNS Servers.  
Is it required to put all AD DNS servers there?  I got two in this case.
Also, is it a good idea to put google dns as 3rd option 8.8.8.8 ?
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I am trying to use per session IPs in an RDS 2012 R2 server (as described here).

My understanding is that this feature will allow each user on the server to have a distinct IP, which might be very useful (for instance) when using a filtering proxy that otherwise might have a hard time to identify the specific users on a single server.

I have implemented the GPO settings as per the article but it does not seem to work so far.

Before going further into troubleshooting I'd like to understand how this feature works. My understanding is that the server will request an IP via DHCP from the local DHCP server at each connexion and assign the IP to the user session. Is that correct ? Or will it actually "self assign" IP without going through the DHCP server ?

If so do we need some "collaboration" from the DHCP server ? Otherwise I presume it will see a DHCP request from a given, non changing, MAC and re-issue the same IP ?!

Also, assuming I manage to have the feature working, is there any way to display all the "User" to "IP" mappings ?
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Free Tool: SSL Checker
LVL 12
Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

How does DHCP work with VoIP phones?  Do they phones need to get restarted every time the DHCP lease expires?  Or it works no different than a regular computer client?
For the first time phones need to be booted to obtain IP addresses.  Also when DHCP or DNS server changes.  What about a regular DHCP refresh at the end of the lease duration?
We use Polycom ip phones over poe.
Please advice.
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I am having machine A hostname responding with IP of B. Same user.  And vice-versa.  In DHCP is other way around.
Tried to sudo dhclient, etc.  Restart, nothing helps.
Both ubuntu machines.
What troubleshooting steps take here?
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How to grab list of DHCP scope, reservation details into excel or notepad in windows 2008
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I just want to disable network adapter by index 27.
PS C:\Users\ad> Get-NetIPInterface

ifIndex InterfaceAlias                  AddressFamily NlMtu(Bytes) InterfaceMetric Dhcp     ConnectionState PolicyStore
------- --------------                  ------------- ------------ --------------- ----     --------------- -----------
21      vEthernet                                      IPv6                  1500               5 Enabled  Connected         ActiveStore
27      Local Area Connection* 12       IPv6                  1300                5 Enabled  Connected         ActiveStore
1       Loopback Pseudo-Interface 1     IPv6            4294967295       50 Disabled Connected       ActiveStore

In network center there is no such adapter Local Area Connection* 12. Get-Netadapter also do not show this Local Area Connection* 12 also.
Wmic  get name, index shows index  27 with name Hyper-V Virtual Ethernet Adapter #2. SO IT IS ACTUALLY 21 index. I cannot disable it with wmic, because i will lose connectivity
How to disable using Get-NetIPInterface, because it is the only place where it is shown.
Thanks
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I'm trying to use a Draytek Vigor 2760Vn to extend a network using WDS. I am trying to use the Draytek router as a AP to extend the current network without having to use extra cables. The network using a BTHub 6 for its main wirless network. The Draytek router is in another room that will have some computers connected the the physical ethernet portds.
BTHub 6 - IP addresss 192.168.1.254, DHCP range 192.168.1.64 -192.168.1.253/24
DrayTek - IP Address 192.168.1.1 using the same SSID as the BTHub

When I configure the DrayTek using the WDS configuration, I scan for the BTHub SSID. Under the AP Discovery, It is found and I click the BTHub SSID selct the Add To button and select it as a bridge.
My goal is to keep all devices on the same network and use the Draytek to replace a VOIP router.
What am I doing wrong?
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Linux DHCP was able to give out DNS search domains.  Windows doesn't.
Cannot resolve by short names after migrating DHCP to Windows AD Servers 2016.
Option 119 DNS Search List not working.  Even though says it design for non-windows client.  Domain names with semicolon.   Still not resolving.
Group Policy wont work because the clients aren't joined the Domain.  

So the only option to tell the users to use a FQDN (long names) from now on.  Some unhappy.  Oh well.  

Any other options?
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DHCPSponsored by Flatiron School

10K

Solutions

14K

Contributors

The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol. DHCP allows for computers to be configured automatically to communicate with each other over an IP network without the need for manual setup by a network administrator. The implementation of DHCP relies on a DHCP server to hand out network configuration information to DHCP-capable clients that request an IP address (and other information required or useful in communicating with other devices on an IP network). In addition to an IP address, common configuration information served over DHCP includes a default gateway, subnet mask and DNS sever(s).