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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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I have a domaincontroller in my network that also acts as a DNS server for my clients. DNS server is given out by the DHCP server.

Of course when the DNS server is down, our clients can't connect to the internet anymore.

I tried in the past to add a second google DNS to the DHCP, but that caused more problems than solutions.

Is there a way to enable a setting so the clients only connect to the internal DNS server when needed (like logging in) and use the google DNS for internet only?
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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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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.
0
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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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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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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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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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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We are having to manually assign the "preferred IP" manually in order to get the clients to connect to the network.  The DHCP scope has 15 IP's available, according to the manager console.  What would cause IP's to stop being assigned?  we're on a Windows Server 2008R2 network.

Thanks for your help.

Damian
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Hello everyone,

After a long electrical lost, the server (windows 2012R2 ) of my client lost power.

After that the Nic team received an address like : 169.x.x.x  here is the steps I take :

1. Remove a nic from the team and put it in DHCP : It receives an ip and can ping google or 8.8.8.8.
2. Once I set an address manually on the card, it loses the connectivity.
3. So I recreate the NIC team from scratch and the problem persist :
No connectivity once I set the IP adress, but once in DHCP, it works

Other info :

I am sure of the gateway, dns, and address,
Do you have any idea where I should check ?

Thanks for your help,
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hello everybody,
I have a DHCP server installed on Active Directory, and second DHCP server installed in additional Active Directory, failover activated between two servers in standby mode, the partner take percentage 5%,
the status is " active" on the active one, and "standby" on the second one.
BUT, DHCP will not work if two servers are up, and works fine if the " standby" server is up and the other one is down


what is the issue and how I can resolve it?




thank you
1
Hi all,

I have recently configured OpenVPN on Ubuntu 16.04.

I can connect OK using my Windows client after transferring the OVPN config file across. I get an IP address via DHCP from the server, but I cannot access any internet pages - DNS PROBE NO INTERNET.

I have noticed from an 'ipconfig /all' that I am not getting a default gateway on the 'TAP Windows Adaptor'

Within the server.conf file, I have the following perimeters:

push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 8.8.4.4"
push "dhcp-option DNS 8.8.8.8"



And within the ufw/before.rules file, I have added the following line:

-A POSTROUTING -s 10.8.0.0/8 -o eth0 -j MASQUERADE


I also have the following defined within my ufw file:

DEFAULT_FORWARD_POLICY="ACCEPT"



I am at a loss, I just cannot seem to route my client internet traffic through the VPN link.

Any help would be greatly appreciated.
0
We are currently having an issue with a 2008R2 server handing out DHCP addresses. It hand out records but then on a  seemingly random basis it stops handing addresses out to a specific client when it tries to renew. To get it working we need to create an exclusion for that specific IP (no MAC) and then try to renew and magically it works.

Some things to note.
- We changed the subnet
- It's a single DC/Server on the network
- We reinstalled DHCP
- We renamed the DC

Error form the client-
Your computer was not assigned an address from the network (by the DHCP Server) for the Network Card with network address 0x10604B5AD366. The following error occurred: 0x79. Your computer will continue to try and obtain an address on its own from the network address (DHCP) server.
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My church has a C2851 that has 3 vlans.  It provides DHCP to 2 of those.  The other dhcp is provided by a windows server.  The server vlan never loses connection to the internet but the other 2 access the internet for a day or two then stop until I reboot the router. Below is the interface setup & dhcp pool.  Am I doing something wrong?

ip dhcp pool guests
   network 10.10.0.0 255.255.252.0
   default-router 10.10.0.1
   dns-server 8.8.8.8
   lease 0 12
!
ip dhcp pool Employees
   network 172.28.0.0 255.255.252.0
   default-router 172.28.0.1
   dns-server 8.8.8.8
   lease 0 12
!
!





interface GigabitEthernet0/1.100
 description Admin vlan 100
 encapsulation dot1Q 100
 ip address 192.168.1.1 255.255.255.0
 ip nat inside
 ip virtual-reassembly in
!
interface GigabitEthernet0/1.110
 description Employees vlan 110
 encapsulation dot1Q 110
 ip address 172.28.0.1 255.255.252.0
 ip nat inside
 ip virtual-reassembly in
!
interface GigabitEthernet0/1.200
 description Guest vlan 200
 encapsulation dot1Q 200
 ip address 10.10.0.1 255.255.252.0
 ip nat inside
 ip virtual-reassembly in
0
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Hi all,

Hope there are some die-hard APC fanatics on this forum :-)

Baught a second hand APC SMT1500I with AP9619 NMC1 network card in it for a very nice price.
Hooked it up and found out quickly that it has an assigned IP adress  (green solid network led).
Tried to set up a connection with hyperterminal and TeraTerm as well in order to reset the IP-settings and password of the previous owner.
Built a RJ45 to DB9 serial cable (http://pinoutguide.com/UPS/apc_0625_cable_pinout.shtml) and bought an USB to RS232 converter.
Hyperterminal tells me there is a connection between my pc (even without being connected to the AP9619) but I get no login prompt, even after many enters and the reset button on the network card (green/orange flashing). So I setup and old XP pc with Tera Term with the same results.

I tried many settings (2400baud 8n1 no flow in each setting, changed pin number 2 and 3 for nullmodem configuration and all the possible varieties. I also connected the PC directly to the network card, changed the network card into static in the same 10.100.0.xxx range (thanks to wireshark network sniffing software that pointed out the adress 10.100.0.55) browsed to this adress and got a message, there had to be logged in via a ssl connection. (of course this didn't worled out well.....). Half a day later I am really stuck...

Does APC needs qualified rocket scientists in order to achieve a simple network card?

Hope that there is a whizkid between all the …
0
I will soon be migrating our AD domain controllers to Server 2016. We have a few DC's in the 1 forest but the one that holds the FSMO also has a lot of other services like DHCP and its a certification authority. I've come up with a very high level list of the process involved, id like to see if I am on the right track by the experts on here. My main concerns are over keeping the same IP and Name as the old DC and moving the certification authority.

The server I'm looking to migrate initially is ADC1

1.      Move services to ADC2
   a.          Move RD Licensing Server
   b.          Move DHCP (or test if we can use the failover DHCP (ADC3) server)
   c.          Migrate FSMO roles
2.      Backup Certification authority on ADC1
3.      Find out what KMS keys are used on ADC1
4.      Remove Certification authority services from ADC1
5.      Turn off ADC1 and test connectivity and logons.
6.      Turn ADC1 back on.
7.      Demote ADC1
8.      Remove all entries for ADC1 from DNS and AD schema
9.      Create new 2016 server (with same IP and name as removed DC) and promote to DC
10.      Upgrade forest schema to 2016
11.      Install certification authority on new DC and restore from backup
12.      Reinstall KMS and keys on new server
13.      Move DHCP back to ADC1 and ensure failover is still working to ADC3
14.      TEST DNS and AD replication.
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Hi all,

Hope you doing good,

I enable the dhcp relay in checkpoint firewall, user are connecting to SSID but not getting the ip address from the DHCP server.
0
Greetings !
     I have a hybrid environment with vmachines running locally and on the web (Rackspace).  With my current configuration I have a VPN tunnel between both environments.  The problem is when I lose power, my internal servers and peripherals crash and when they are brought back up it is hard to get DHCP services back online, bring up the tunnel,  etc.   Is it possible to set it up where my internal servers fail over to another DHCP server I could set up at Rackspace?  The advantage being that once power is restored they could instantly get leases, etc.  Is this something covered in the 2012 MS server DHCP functionality?  Ultimately I would like to set something up which "takes care of itself".

Thanks,

Eric
0
Hi,

I have interview at microsoft GTSC. can some one please share me case scenario and troubleshooting questions on below topics.

I know the basics, just looking for troubleshooting scenario based questions on the below topics. thank you.

1)  FSMO Role
2)  Active directory site, service and replications.
3)  DNS
4)  DHCP
5)  Group policies
6)  Replications issues, log analysis,
7)  migration Ad
8)  authentication policies like  kerbros, LDAP
0
Customer has an Arris DG3270 (cablemodem/4-port router) with a switch connected to one of the 4 LAN ports on the Arris router.  Symptom is occasional (random, a few times per day) the devices connected through the switch lose connectivity (yellow triangle shows).  Devices are CC terminal, Win7 POS term, Mac, Win7 PC.  Devices connected directly to the router retain connectivity.  We can restore connection to switch devices by unplugging the Cat5e cable between the router and switch and reconnecting it.  We've tried changing the switch (Netgear, DLink, TPLink), but the symptom persists, so it seems likely the problem originates with a device connected to the switch.  I've run RogueChecker to see if there's more than one DHCP source, run IP Scanner to see what it finds on the LAN.  Nothing looks out of the ordinary.  Any suggestions on what else we can try or check?
0

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).