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 Cisco Aironet 1602i-e-k9, I have configured it (attached config) and I wanted to assign the DHCP pool Wifi (created in the config) to assign it to the users. It works if I put the IP address in manually but I wanted to have the AP do the DHCP leases.


Thanks in advance
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I Need help for cabling. I do not know whichcables connect  to trunk

Plan: i wan to connect my HP Switch to 2xesxi Servers. I have a 2x ESXI Server each 3 physical NICs

esxi1 -         vmnic0,vmnic1,vmnic2
esxi2 -         vmnic0,vmnic1,vmnic2
on HP 3400cl Switch:

ip Routing enabled
dhcp helper on vlan 10,20 enabled

Vlan 1 -   DEFAULT                   port 1-4
vlan 10-   ISCSI                         port 6-12
vlan20-    MS DHCP Server    port 13-18
TRK1 port 19-21
TRK2 port 22-24

I am stuck here , which cable should i connect to esxi1 and 2
I have this unusual problem in a Virtual Box Server...  For some reason the 2nd networking device does not connect on boot up and there is an error when I issue the command:
sudo /etc/init.d/networking restart

However if I use:   sudo ifconfig enp0s8 down  followed by sudo ifconfig enp0s8 up  
then I am magically connected.

I know I'm good because I can or can't ping the gateway  (and the host computer can ping back the Virtual Machine)

I would also appreciate any info on how you went about diagnosing the problem.

Here is my interfaces file
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# To restart interfaces sudo /ect/init.d/networking restart

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto enp0s3
iface enp0s3 inet dhcp

# The secondary network interface
auto enp0s8
iface enp0s8 inet static

and here is the  pertinant section from journalctl -xe
-- Subject: Unit networking.service has begun start-up
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
-- Unit networking.service has begun starting up.
Feb 07 20:17:58 personalserver1 ifup[1462]: RTNETLINK answers: File exists…
This is an addendum to an old ticket which can be seen here:


The problem described in the old ticket is still occurring. Random devices will pull a 192.168.0.X address. I put in a new Unifi network (With a new Sonicwall) but the exact same thing is happening. The DNS server changes as well. The DNS server on the firewall is listed as, which is exactly what devices that pick up the CORRECT 192.168.1.X subnet read. However, those that get the wrong 192.168.0.X subnet read the DNS server as, which is the old TW/Spectrum DNS. I have no idea how it's grabbing this.

This "wrong subnet" problem only appears to occur with the wireless devices, as no hardwired device has shown this error so far. That leads me to believe it's either a setting in the Unifi setup (For which I've kept all of the defaults) or the way the Unifi is talking to the Sonicwall. To combat this problem with laptops I've gone in and set static IP addresses from the PC side, which seems to have corrected the problem.  However, with the Nest devices, this isn't an option, as there is no way to manually enter network info.

Instead, I created a  static IP for the Nest devices on the firewall. If I reboot the devices they SOMETIMES pick up on the correct subnet, and when they do, it's the static IP I gave them in the firewall. However, after a few days of working properly they …
Best way to provide a users read only access for below
AD Groups
DNS entries
DHCP scopes
I am new to managed switches.  I have never had to set one up.  So I am not asking for the answer directly, but maybe some guidance/online tutorials.  I have printed out the manual and I attempted this setup yesterday.  After 18 hrs and still not internet and me not getting anywhere, I am now going to reach out and see if I can get some guidance.  I have setup a DLINK DES-3528, and it is currently in production, but only default VLAN can get DHCP and I there is no intercommunication between VLANS.  I have drawn up a network map on what I am trying to accomplish.  I am still going to write out what I am trying to accomplish, but the network map will help with a visual.  I will say that I have successfully set up the firewall with VLANS and static routing.  So I do have basic knowledge.  

Port 1 on NMD Setup

Internet -----> Firewall from ISP.  IP is a static assignment.
VLAN 1 -----> Public Access (
VLAN 100 ------> Phone only (

I do have access to this firewall, but I do not change any settings on it due to the ISP manages this firewall.  The ISP is a smaller ISP and I have a good name with the company so they gave me access to the firewall.

Port 2 on NMD setup

Internet ---> Fortigate 60E WAN.  IP is a static assignment.
Fortigate Port 1 -----> Cisco switch.  Port 1 has a total of 5 VLANS configured on it.
Port 28 assigned to VLAN 1 (Default ----> No DHCP
Port 1-8 assigned to VLAN 100 (Domain …
Wi-Fi not connecting. I get a message that says Wi-Fi is on limited connection but cannot get to the internet. I take this to my house and the Wi-Fi pops right on. In trouble shooting I get errors Wireless does not have valid ip configuration. I checked the properties of the network and it is DHCP and set to auto config when I do an ipoconfig /all? I know the password is correct?
I have setup an RDS Personal Virtual Desktop Collection using a nested Hyper-V server (Windows 2016) under Azure. Azure is using Azure Active Directory Domain Services, which can provide DHCP addresses to any Virtual network created within Azure. However, in the Hyper-V nested server, I have had to setup an internal virtual network for the RDS Desktop Collection (5 x Windows 10 Pro workstations). In an non-Azure AD Domain Services network, it would be simple to set up a DHCP server on the Hyper-V hosting server to provide IP Addresses to the virtual network. However Azure AD Domain Services will not allow a DHCP server to be activated as no AAD DC Administrator has Domain Admin privileges.

So has anybody achieved either setting up a DHCP server in Azure AD Domain Services or have you managed to link the nested Hyper-V virtual network back to an Azure virtual network/subnet so DHCP addresses can be provided to the nested virtual network and therefore the 5 workstations connected to it?

It does work using the Hyper-V virtual network switch configured with a static address and NAT'd with a Class-C subnet but each workstation has to be configured manually with an IP static address.

Any suggestions or solutions would be gratefully appreciated.
DHCP Server Logs stop logging when the file reaches 10MB in size and at the end of it states "Audit Log Paused"

I've manipulated the registry value here: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\DHCPServer\Parameters\DhcpLogFilesMaxSize and set it to 125 in decimal format.

Regardless of what size i've set -- the log caps out at 10MB and then pauses.

Any ideas?
I am attempting to configure a DHCP failover using server 2012. I am receiving an error that reads

"The specified DHCP client is not a reserved client. Configure failover failed. Error 20018. The specified DHCP client is not a reserved client."

Any ideas why I am receiving this?
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1 DHCP server running Server 2016
1 Master name server - not a DC
4 DCs all running DNS - both active directory integrated and regular DNS

I'm helping troubleshoot an issue with DHCP failing to register DNS updates.

I'm pretty sure DHCP is setup to register DNS on behalf of the clients. See my screenshots below of IPv4 Properties. I have also configured the update registration credentials -- the account used there is a member of the DnsAdmins group. I have also placed the DHCP server in the DnsUpdateProxy group.

Here are some errors I'm seeing in Event Viewer:

PTR Record registartion for IPv4 address [] and FQDN test-fqdn.test.net failed with error 9005 (DNS operation refused).

PTR record registration for IPv4 address [] and FQDN test-fqdn.test.net failed with error 9004 (ENS request not supported by name server).

I've researched these errors but haven't had much luck.

Here are some error's i'm seeing in the DHCP logs:

DNS Update Request,,test-fqdn.test.net,,,0,6,,,,,,,,,0
DNS Update Failed,,test-fqdn.test.net,,,0,6,,,,,,,,,2

Any help is much appreciated and thank you in advance.
I just added a new 2016 DC.  It has DHCP and DNS, Global Catalog and is the PDC
Went through all the steps to properly remove the old DC.  Moved FSMO and ran Dcpromo (2008 R2).  The old server removed without problems.

When I try to access computers via the domain name, sometimes I can, sometimes I cannot.
If I use the IP address it works fine.

It has been 3 days since the new DC was added.
I've checked DHCP and DNS and do not see a problem.   However, I must be missing something.
Other than not being able to access the computers by name, there are not any reported problems.

Where do I start looking to solve this.  It seems to be a DNS problem, but I cannot identify it.
Is the "Split Scope" going to AUTOMATICALLY start issuing IPs from the down server's range (i.e. 151-200) when the only working server's "DHCP" (i.e. 100-150) range is "100%" in-use or do I need to MANUALLY expand the working server's range when the other server dies to be able to use the entire range on one server ?

I currently have two test DHCP servers setup on a "Split Scope" that work fine, issuing IPs when the other server is down

 1. 1st "DHCP" server's - range is down
 2. cliet IP gets issued from 2nd "DHCP" server's - range
 3. 2nd "DHCP" server's - range is down
 4. cliet IP gets issued from 1st "DHCP" server's - range
I had this question after viewing DHCP Find is picking up a rogue server.

I am experiencing the exact same issues as the gentleman in the posted link. I'm seeing DHCP offers from a IP address (which when looked up originates from China) Here's the caveat...The offers are IP addresses in the range configured in our regular DHCP server. There is no traffic captured in Wireshark from the IP address and there are no ARP entries anywhere with that IP address. I also have that IP blocked at the firewall. The accepted answer to that post was to see if there was a BLU phone connected to the network somewhere. There was no confirmation that this was actually the case. Anyone out there have any thoughts or ideas that they can send my way? I'm at a loss here...
we are finding  on DHCP server below

Windows successfully diagnosed a low virtual memory condition. The following programs consumed the most virtual memory: mcshield.exe (1776) consumed 311754752 bytes, svchost.exe (1324) consumed 179965952 bytes, and svchost.exe (964) consumed 99065856 bytes.

these events are generated every 5 mins once it reaches its maximum state that is when server goes in to the soft hang mode

an event 7031 generated which is below,

The DHCP Client service terminated unexpectedly.  It has done this 2 time(s).  The following corrective action will be taken in 300000 milliseconds: Restart the service

we noticed the 7031 event for dhcp server service terminating at 10:01:18am and we saw the 7036 event saying dhcp server service entered running state automatically at 10:01:31AM. So in the traces also MS saw that dhcp server is serving client requests after 10:01:31AM. But as per our observation, the clients did not get IPs from dhcp server until 10:13AM when we manually restarted the service again. We are not sure why the clients were not able to get the IP address while MS clearly states In the trace that dhcp server is responding to the client queries.

any reason  as to why clients were not getting the ip's
Hi, I created a scope in dhcp server, the scope have configured an address pool for distribution of 55 IPS.
the statics show total address 55 and in use 55, the scope is full used, but the Adress leases show only 10 IPS.
why not show the total ips in use?
any ideas?
We have a Fortigate 101E Security Appliance.  Port 1 is connected to a LAN with a DHCP Server running on a Windows Server 2008 R2 computer.  The DHCP server hands out addresses from a subnet.  Port 10 is configured with a DHCP Server enabled that hands out an address from a subnet to a laptop connected to that port.  There are static routes and IPv4 policies entered so we can successfully be on one subnet and ping an address on the other subnet.  However, there is no name resolution yet.  The DHCP server enabled on port 10 is handing out the address of the DNS server on the other subnet ( but when the laptop gets handed a 172.16.X.X address (and the address of the DNS server 192.168.X.X) that address is not registering on the DNS server of the subnet.  How can I get addresses on the network to register on the DNS server of the network?
Hi all,

I'm looking for a bit of help getting started with my HP 1820-24g switch .

my network plan :

sophos router eth1(lan and i configured the sophos router so : new interface eth4 ( mit VLAN ID :10 function.

i also sophos router configured dhcp scopes for to 200

so i connected sophos eth4 lan cable  -->switch port 1

so i have the native vlan 1, and  vlan 10(port 1-10 tagged) for lan  on the router.

my problem are:
1. if i change sophos interface(eth4)  Vlan funtion to only ethernet and i connect my laptop port 7 then get my laptop IP from sophos router dhcp server.

2.if i change sophos inteface (eth4) only Vlan fuction (vlan 10),then my laptop gets no ip from sophos dhcp server.

any idea and help?
Thank you
i have a HP ProCurve 3400cl .I factory reseted ,but now i can reach switch any more . I thought it get automatically IP from my DHCP server. If i connect one of switch port my laptop,my laptop gets automatically IP from dhcp server, but i need to configure switch.
there is a serial port DB9 on the switch but unfortunatly i have no cable for it.

i looked arp and my dhcp server releases  but no clue of switch.

what can i do ?
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The problem occurs when the computer is restarted or turned on, causing loss of IP. It is reviewed and there is an IP that starts with "169. ..." or that is duplicated.

This problem occurs with both static and dynamic IP addresses (dhcp).

It is solved by disabling and re-enabling the network or reconnecting the network cable.

The problem occurs in different computers, especially in win7.

The DHCP server is a Cisco 3650x

We await your help, thanks.
Hello everyone,
I just had and issue with a client where I ended up having to change the DHCP scope and network id.  I have changed the DVR to match the network and then after that it is now prompting me any anyone else to tries to log into it or make any changes with an admin username and password and I know I did not configure it to do that.  Also no one knows who this was purchased from which makes this even more challenging.  I have reached out to a camera company to see what could be done and then he recommended that I do a firmware upgrade to default factory reset it and the website he directed me to did not have any firmware for that device.  Does anyone know where I can either find  a firmware update or somehow default factory reset it.
I have 2 DC's running win 2008 32bit also Running DNS, DHCP with Domain Functional Level of Windows Server 2008.
I want to introduce a Windows Server 2012 as a DC and transfer the FSMO but I still want to keep running DNS and DHCP on th eolde 2008 32bit servers. ANY recommendation as of what steps should I take and should I also move DNS and DHCP to the new server?
Looking for a script that will go out and check if DNS is SET to DHCP. The script will run against all the computers in the network.  The output should only contain the name of Computers that are not using DHCP Option for DNS.

Thanks in advance
Hey guys,
I am dealing with a client that has been down all yesterday as well as today with conflicting IP addresses.  I worked with Microsoft and they were able to find the mac address of another device that was giving out DHCP.  I have tried arp on various servers and could not find that mac even after pinging the broadcast address.  I have tried this command: show ip arp vlan (vlan number) | include (mac address) and all that it can really tell me is what the originating port is.  This lead me to two HP switches which also have the mac address but that list the trunk port as the originating source. I am getting absolutely no where with finding this.  Please help!!!!
I have Windows Server 2012 and I've been planing to install DHCP server in Windows since I have DNS and Domain in that server, but my networks utilizes switch's DHCP and I am wondering what is the best practices to manage DHCP is it to use core switch's DHCP or Windows Server DHCP?






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).