DHCP

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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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If I want to find out if a ip address is set to DHCP or staticl on a workstation Win7 - remotely.
I can ping and use tracert successfully.

What type of Windows tool can I use at a DOS prompt or CLI from my computer.
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Currently I have Spectrum modem / router . one port has DHCP enable with a dynamic public IP that is connected to a switch and all devices use that.

Anther port on the spectrum modem / router is connected directly to one computer that has a STATIC public IP and is working fine.

I want to use the Ubiquiti Unifi Security Gateway (USG) to be my router and have the specturm be just a Modem.

When I change the router/modem to be just a modem and connect it to the USG the regular network is fine, but that computer that has a static public IP can't get online .

Suggestions ?
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I have a wireless modem/router which manages the main part of my network.  Its LAN IP is 192.168.1.1 and it is a DHCP server.

I have also connected a TP-Link C60 Wireless router via cable to the modem/router.

I am wanting to configure the TP-Link wireless router to give wireless access but then have the DHCP managed by the modem/router.

At the moment I have the TP-Link router getting a WAN IP of 192.168.1.200 from the modem, but then the TP-Link is issuing IPs to wireless clients in the 192.168.0.1 scope.

Does anyone know if I can get it to simply act as a wireless repeater for the modem rather than have its own DHCP scope?
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Hello.

I have 3 VLANs and one DHCP scope on Windows server. I need to make it work together.

Layer 3 Switch config:
int vlan xxx
ip address 192.168.94.1 255.255.254.0
ip helper-address 192.9.102.10
no ip proxy-arp

Any help appreciated.
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What are the steps to add IP address DHCP MAC address reservations to a SonicWALL TZ 600 router?
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A business client of mine has switched internet service providers and the new provider has installed a mikrotik rb2011il-in.

How do I configure DHCP options for Gateway, DNS using Webfig.  I cant find anything on the web about the task that is recent and from I can only assume is a hobby router
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2 x HP laptops Windows 10, unable to connect with Ethernet cable not able to get an address via DHCP. Setting a static IP address does not resolve the issue either.

This happened two months ago in which I was able to fix I'm suspecting Windows update keeps upsetting it
All the cable side of things have been tested I believe updating the BIOS fixed it last time.

Any thoughts or if you have experienced can you please share?

Im going back onsite now to see what else can be done so if you see this and know the answer if you could please share.

thankyou.
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We have a situation were one of the rouge DHCP device was attached in client network. What will be the affect on actual DHCP server, in this situation.
DC is windows 2008

I saw a event id 1046.
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We have a few thousand laptops they all seem to be working fine. I have one windows 10 laptop this morning that can connect to an ssid and gets an ip from DHCP but cannot do anything else.  It cant ping anything or connect to any websites.  I can connect the laptop to another ssid and am able to connect to the internet without issue. I deleted the DHCP entry for the computer and released and renewed the ip on the laptop but still has the same issue. I uninstalled and reinstalled the wifi card in device manager.  Any ideas on what I should do?
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Hi ,
 i was wondering if any one knows the work around to make WDS server communicate with client when Netbios is turned off from DHCP scope settings and Netbios is enabled  on on WDS server.

Thank you
Samso
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Hi, We have a requirement to create additional 150 scopes in our Windows DHCP server (Windows 2012 R2). The file contains IP range (start and end IP), subnet, default gateway, lease duration, scope name and description.

DNS servers (option: 006) and DNS domain name (option:015) are already part of server option.

Kindly note, our DHCP server already have 50+ scopes and we want to add more (i.e. 150 scopes new).

Appreciate help to provider a script  (PowerShell, vbs etc.)to add scopes to the DHCP server.

Regards
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One of my clients has a Telstra DOT phone system. I have had a Telstra Tech onsite for several hours and each time he gets his System working and then plugs in the Server to the network the 3rd line on the Cisco box drops out. When he disconnects the Server and reboots the Cisco box the 3rd line works fine but the 3rd line drops again once the Server is connected to the network...Please explain.

The Server is doing DHCP and Option 66 is enabled and configured in the DHCP scope. Turning off DHCP on the Server and setting it on the router doesn't make a difference

Hope this makes sense
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I have 3 DNS servers. Each server is in its own subnet. It appears that the Primary DNS server is not deleting old records. We have duplicate IPs on one particular DNS server. I have scavenging turned on.  
Select the Enable automatic scavenging of stale records check box is checked. The Enable Aging and Scavenging for DNS  is checked. The other 2 DNS servers are removing old records.

Could the db be corrupt? Should I delete the duplicate records? That would be a time consuming task.

DLH
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We have recently taken over a clinic. They have their own Windows SBS server that handles DNS, DHCP, AD, etc. They have other servers that they need to continue to access. Temporary I've added a firewall and established an OpenVPN connection with our data center. The users have been given domain accounts for our network. Now my boss wants to add their computers to our domain.  The goal is to for the computers to have access to both networks and users login with their new domain credentials. My initial idea was for computers to keep the local DHCP address and change the DNS to point to our servers. I also configured a NAT for each computer (10) on the tunnel. I can add the computers to the domain but it takes users 10 minutes to login. How do I get around this without adding an additional NIC?
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Our DHCP servers host multiple scopes for ip address leasing.   I am not very familiar with the newer iterations of DHCP server 2008, 2012, etc.  I noticed that if I right click on a lease I can apply a deny filter to the device.   Does that filter only apply for that particular scope, or will it deny  access to DHCP lease entirely?
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One of my client computers is giving us difficulty when trying to RDP into it.  I can ping the machine & get a response, where I'm confused is the IP that's returned doesn't match the host name.  I ran ping -a to check this, which returned a host name that was joined to a domain that has been decommissioned for well over 4 years.  Ran nslookup of IP it returned the same odd host name joined to the current domain.  Then I ran nslookup using the odd host name it then returned the odd host name, joined to old domain.
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We have a Class C network and are running out of IP addresses.  We have multiple switches throughout our company and don't want to incur the expense of upgrading all of them to be VLAN capable.  In order to expand our addresses, is it possible to only upgrade one of our switches to a VLAN capable switch and configure it as follows:
1.) The DHCP server is plugged into one of its ports which is configured to be on the default VLAN.  
2.) Any other switch plugged into it will be plugged into a port configured to be on the default VLAN.  
3.) Any other device (printer, computer, etc.) plugged directly into it will be plugged into a port that is configured to be on a secondary VLAN.
4.)  The DHCP server is configured to hand out a different scope of addresses for devices on the secondary VLAN.
5.) The switch is configured so the VLAN's can communicate with each other.

Again, if all we need to do is expand out addresses, is it necessary that any of the other switches are VLAN capable?  Does anyone have a alternate, perhaps simpler way of expanding the addresses?  We could convert to a Class A or B network.  Please advise, and thanks in advance.
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I am trying to document the steps to restore the DHCP server to another in an emergency in case if the existing server fails.
I read few kb articles and found it looks simple procedure, they are about restoring the backup and authorizes the new DHCP. We have NAP server in place and DHCP is running on a DC also.
Should we have to give new DHCP server with the same IP as the old server? I am the concerned here because if the existing DC went down then the AD will still have the information about that server. In an emergency, I would not have time to clean the metadata, I guess  I should not give the same IP as the old DC's. Does the old IP matter to DHCP clients?
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Trying to narrow down issue with machines getting DHCP leases. Could be machine, or DHCP relays.

Is there a way to test the DHCP server itself to make sure its part is working correctly? I checked logs, and everything seems to be working fine but is there something like dcdiag that could verify? I dont manage the other parts, just the DHCP server itself so I have to make sure its working correctly. Thanks
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Folks,

I'm migrating from SBS 2011 to standalone Windows 2016 servers.  I have migrated mailboxes to O365, added 2 additional DCs, file and print servers etc and moved across file shares etc.

I have also added a DHCP role on DC1 and disabled the service on the SBS. It has remained this way for over 7 weeks.

The other day, I uninstalled Exchange 2010 from the SBS as part of the migration process and left it like that for 2 days.  I got a call to say all stations were unable to connect to the network with 'unidentified network' errors.  I discovered that DHCP was unauthorised on DC1 and reactivated on the SBS.

I checked the DHCP log on the SBS and the last entry was on the day that I disabled the service,

How could this have happened?  I've done loads of these migrations from SBS and never seen this happen before.

Thanks
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Hi There,
DHCP fail over not assigning addresses when 1 x off dhcp is turned off
Here my set up

2 x networks
-> First Network
192.168.1.0/24
DC & DHCP role installed

-> Second Network
192.168.2.0/24
DC & DHCP role installed

Site are in different physical location & connected via site to site VPN
Ping between both network OK

I have setup my DHCP failover exactly like here:
https://technet.microsoft.com/en-us/library/hh831385(v=ws.11).aspx

When I turn off on of my DHCP server for testing purposes, the DHCP orange appears, but that is about all that happen. No ips are assigned.
Any ideas?
Thanks
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At my office all of the computers plug into a central Dell switch that connects to the X0 LAN port and should be getting DHCP address from the 100 subnet.  On Monday we had a computer that got an DHCP address from the 180 subnet so we put that computer on a static IP and thought the issue was resolved.  Tuesday we got 2 more computers that recieved IP addresses from the 180 subnet so we just removed the DHCP hoping that would resolve the issue.  Wednesday we had two more computers get incorrect DHCP addresses.  On my computer I got an 160 subnet address, then I reset it and I got a 99 subnet address.  Finally, I put in a static IP so I could work.   Once I was able to, I set my computer back to DHCP and yesterday afternoon and again today I got the correct 100 subnet address but today another computer got the 99 subnet IP address.

I am using a TZ600 with Firmware Version SonicOS Enhanced 6.2.7.0-19n.   I do not have any portsharing set up (I did contact sonicwall support to confirm this).   On Sunday we copied the settings from an NSA 250 which had 5 ports and an expansion card with 5 additional ports.  We did need to change the port number for the last five from M0X1 to X5, MOX2 to X6, etc, and then change the zone names in the FireWall Access Rules. Here are the listing of what is on what port:

X0 - primary LAN 192.168.100.1 (has own DHCP)
X1 - WAN
X2 - Separate LAN (used connect a separate sonicwall in a location without internet)
X3 - WLAN (sonicpoint) …
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Here is our setup two Windows 2012 R2 DHCP servers in a fail-over relationship both of which are active. Our DNZ zone is set to secure and non-secure DNS Updates. When I view the owner of a client DNS record I see it listed as system which from my research "should" be the DHCP server. We are currently not using DHCP option 081. If a client is handled out a lease then is powerd of or moved to another location we have seen issue where the clients DNS record is not update with the new IP.

If DHCP option 081 required to all the DHCP server to full main and clean up DNS records for clients?
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Hi, I am working at a site and am having active directory and DNS issues. I found a script that ran a lot of diagnostics on the AD server. The output is attached. I am far from a AD / DNS server expert so any help I can get would be much appreciated.

A number of changes have been made in this environment by a number of individuals so I am a little concrened with the current state.

Here's what I know about the site:
Ths site has AT&T business DSL service for internet connection. They are running Server 2012 R2. The server was setup with AD/ DNS and DHCP initially, but someone uninstalled DHCP because they could not get the internet and DNS working without the users getting DHCP from the Watchguard firewall device. Like I said, a number of foiks have had their hands in the pot, and I am coming in trying to figure out what they did.

The company has moved to a new site. The configuration is the same as above, except now they are not using the watchguard firewall device and are all connected via direct connect, a switch and wireless to the AT&T modem/router. They are also getting DHCP from the AT&T device. I am seeing a number of issue with devices and the server not resolving to nslookup. I upgraded a Windows 10 Home laptop to Windows 10 Pro, but I don't get the Join a Domain option. Not sure if this is because the domain is off, or there is another with the OS on the Laptop.

They have purchased a Dell SOHO firewall device that I need to install, My thoughts are to …
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Hello,

We've recently deployed the CIS L1 computer benchmarks for windows 7 and 10.  I've run into an issue on a subset of machines receiving ip addresses.  Occasionally, they will not grab an ip address via dhcp on wireless or wired.  It doesn't matter if the user is at home or in the office.

I ran wireshark to see what is happening during the dhcp process.  The discovery and offer occurs, but I never see the workstation send the request.  The discovery and offer occurs a few times then ultimately times out.

Has anyone seen this behavior before?  I'm assuming this is an issue with one of the gpos we pushed out for CIS since it coincides with the CIS deployment and occurs in and out of the office.
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DHCP

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).