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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rpi3b,  Stretch, used this tutorial for setup:


Except that I added an entry in /etc/dhcpcd.conf to make br0 ip address static (found that in another post):

interface br0
static ip_address=

Open in new window

ifconfig output on rpi:
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet  netmask  broadcast
        inet6 fe80::a8b1:dbf2:1ff6:c1d9  prefixlen 64  scopeid 0x20<link>
        ether b8:27:eb:8b:27:c0  txqueuelen 1000  (Ethernet)
        RX packets 684  bytes 112300 (109.6 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 302  bytes 33198 (32.4 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet  netmask  broadcast
        ether b8:27:eb:8b:27:c0  txqueuelen 1000  (Ethernet)
        RX packets 384  bytes 62532 (61.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 631  bytes 97466 (95.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet  netmask
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 260  bytes 22236 (21.7 KiB)
I have to switch my LAN to a new ip range. I am using DHCP service for most workstations. If I plan on using say for example .2-.50 as static addresses is it best practice to configure the pool as .51-.100 or configure the pool as .1-.100 and exclude .1-.50?

Also, what are the advantages and disadvantages to reservations as opposed to static ip's?
I have two file servers running server 2012 R2, Server1 and Server2.  They are both configured as AD, DHCP, DNS servers.  Server2 hold the FSMO records. DFSR is deployed.

I have DHCP configured for failover  if either server should go down for some reason.  The Options replicate from Server2 to Server1, but the leases and Reservations do not seem to update, and I cannot add a reservation to server1.

When first set up, the list of leases and reservations seemed to update from either server.  

The mode is Hot standby.

What are the best practices for DHCP failover?  There are up to 50 users connected to the network

Obviously this will not function as a hot standby because if Server2 failed,  Server1 would not have the reservations necessary.  Creating reservations is necessary to accommodate the network scanner that directs scans to a specific IP address.
Simple WAN - 3 sites, one main and two remote sites connected via a MetroE with Cisco routers.  IP address of cisco router is at a particular site...

Each site has sonicwall to ISP internet.  For this example, sonicwall is  DHCP is handled by sonicwall and default gateway for network is  

Is there anyway to have the default gateway change automatically should the internet go down at a remote site.  For example, Internet goes out at the 1.x network.  If I manually change the default gateway to 1.253, then devices would use MetroE to access Internet at main site plus all other devices over the MetroE.

I need this to happen automatically.  I could make the internal MetroE cisco router as the default route but again, on the fly how would I route "unknown" traffic across the MetroE should the local Internet go down?

Experts out there , I have a question about DHCP server and hope someone shed the light on it.
We have a DHCP server running on Windows 2012 server (not fail over mode).  The lease is set to one month.
What will happen to client PC's  IP if the DHCP server unavailable?
Will the client PC keep the IP remain same when we reboot the PC?
it will loose the IP since the DHCP is not available to validate ?
On two separate projects in two separate companies I have become aware of an issue where AD information from a long time ago, seems to revert back into AD.  In case A, a DC had been removed several months prior, and then Bam!   it looked like there references in AD to the "flying dutchman" AD server.  In case b, the event seems to revolve around a switch reboot.   In this case AD information from YEARS ago returned (We think the information coincides to the point when the systems were imaged and first brought into the domain (like 6 years ago))  I did note that one of the DC was not responding to dns queries via nslookup, and workstations on a specific subnet seemed to revert from DHCP subnet IP to a 169 address.  Immediately after the event rebooting the workstations still left the system with the 169 addresses.  The switches involved are Cisco switches and the subnet has an IP helper for the interface.

I don't have specifics on what happened, I am just trying to understand what causes an event like this.
Hi Experts,

We are planning to demote a server running Windows Server 2012 R2 which is also a Domain controller. (i.e removing AD domain services etc and shutting down the server).
This server is also a DHCP server and was wondering if it’s possible to replicate the DHCP scopes configuration and DHCP scope options configuration onto another server? (ie. So that this service is setup on an alternative server so that the DHCP service is not disrupted)

In Windows 2012 R2 DHCP Scope policies, what is the difference between Vendor Class and Client Identifier? I have some devices that I need to setup a separate policy for and got the vendor id  from the vendor yet when I select vendor class, it has a drop down with only Microsoft options. Client Identifier does let me type information in though.

We have two DHCP servers, the OLD server and the NEW server.  We'd like to migrate to the NEW server, but we cannot get it consistently deliver IP addresses to our various subnets.

We have all of the appropriate IP-Helpers in our switches.  The behavior is as follows:

We are using Microsoft Server 2016 with Microsoft DHCP Server.  The server sits on ESXi host.  (different host)

1.  We turn off the OLD DHCP server and turn on the NEW DHCP server.  Scopes are enabled.
2.  In some cases, users will get new IPs right away.\
3.  In some cases, users never get an IP, they get a 169.254.x.x address.
4.  In all cases, if we switch NICs on the user's computer, they will get an IP.  For example switching from the docking station NIC to the laptop NIC will always give an IP from the NEW server.
5.  We can usually find the following message in the logs: "Your computer was not assigned an address from the network (by the DHCP Server) for the Network Card with network address 0xF4D108E45BA6.  The following error occurred: 0x79. Your computer will continue to try and obtain an address on its own from the network address (DHCP) server."

Any suggestions?
having recently had problems on our windows 2012 r2 dc, we carried out quite a lot of troubleshooting and resetting if things. one of them was to remove the virtual nic and add it back in again.

since then, when we reboot a client it cannot pull through ip addresses using dhcp. if i configure the ip manually, it works fine.

can anyone advise whether replacing the vm nic should affect dhcp, and if so how can i resolve this?

any suggestions much appreciated.
What is a better design regarding a company wireless network?

At my work we have 2 Guest Wireless Networks.  

1.  Guest Wireless (SSID) (
2.  BYOD Wireless (SSID) (

These 2 SSIDs are not routed to our company network in any way.  We have 2 wireless routers/controllers for high availability, our corporate network SSIDs provide DHCP from our internal DHCP server; but, both guest wireless SSIDs use the controllers for the DHCP server.  The only problem is that

Controller 1 has 1/2 of each individual DHCP scope and it has the default gateway of 102.1 and 103.1

Controller 2 has the other 1/2 of each individual scope and it has the default gateway of 102.127 and 103.127.

The Wireless Guest Lans work great and they have no connection to the corporate network; but, I noticed that if either controller is off-line the guest users must do an ipconfig /release to clear out the IP settings (default gateway for that SSSID in order to receive the correct IP settings from the other controller (Controller 2).  Hence the guest access is not a seamless fail-over process.  If you are connected to a controller 2 ( a unique gateway IP address) and already have controller 1's Default gateway ip address cacahed in memory … you will not be able to connect to the internet from controller 2 until you perform an ipconfig /release.  

Is there a better way to design the Guest Wifi Access for these 2 x GUest SSID's?  Currenlty we have 1 older WiFi …
Good Evening All,

This is my first post to Exchange Experts. I always tried to find my way by trying different solutions to the issues I had however I ma now facing DHCP issue on our new site with sonicwall product I have never used. Never used sonicwalls at all.

So I have below interfaces set:
Sonicwall Interfaces Config
At this site corporate WLAN on X2:V20 is our corporate WIFI with DHCP served from SonicWall with range 10.0.3.xxx to
X0 with subnet is a Corporate LAN with DHCP served from Widnows Server 2016 deployed by me with subnet range 10.0.0.xxx to

Now I have to merge those so the WLAN network take DHCP from the Windows server instead of sonicwall.
Sonicwall Model: NSA 2600

Any suggestions please?
Dear Experts,

I have a question regarding to the Window 2012 R2 server DNS, AD, and DHCP setup. Say I have a server setup with the these services DNS, AD, and DCHP. If I wish to configure a failover or a copy of this server, what will be a good way to setup? If I do need to setup another server will I need to keep it up all the time so in case the main server fails the backup can take over? How will I know if the user are on the main or the backup? Will the backup server cause conflict with the main server? Thanks. (sorry that I have so many question in one)
I have setup a failover DHCP server configuration in Hot standby mode between two Windows 2012 R2 servers in the same subnet. The Max Client Lead Time is 5 minutes and the State Switchover Interval is 15 minutes. The addresses reserved for standby is 0% because we don't have enough addresses.

When I stop de DHCP server on the primary server after 15 minutes the hot standby server switches the scope over to partner down and 5 minutes later it's serving out IP-addresses. Only now comes the problem / fun part. The stand-by server is leasing out correct ip-addresses from the scope, but it does it with the 5 minutes lease time as configured in the MCLT. He does this for the entire time the Primary server is down. So every 5 minutes it leases the same ip-adres to the client for an other 5 minutes. over and over again.

Is this normal behavior? I thought that after 15 minutes of switchover interval plus the 5 minutes of MCLT it takes over the complete scope and acts like it's the primary server.
Ive a new netgear jgs524PE switch and a netgear orbi rbk50 I would like help to setup correctly.

Currently the isp router is giving a gateway on one port of that runs to the Netgear orbi, The orbi in turn has created its own network on, my switch is connected to the orbi with an ip

I have nas connected to the switch, previously it was on but I guess that now needs to be changed?

What is the best way to set up here? The Orbi provides netgear circle which allows me to control the kids devices with devices on the orbi network. So I think the switch has to stay as currently connected.

I am not sure if I should have the Router providing dhcp.

Your advice would be welcome.

This is a home setup but I do require 1gb cable speeds as I zoom a lot. The  synology nas server needs to be accessible from outside.
I have a server that has an IP address that was static but somehow changed after reboot was done on it.  The address was reserved on another DHCP server to prevent it from being used.  I am finding when I change the IP back to the static address it had, I get an IP conflict error showing up. I pinged the IP address on the LAN and I confirmed it is not being used by another device.  I was thinking DHCP is probably preventing me from using that address at this point so I tried disabling DHCP temporarily so I could then change that server IP back to it's static but I am still getting the conflict error.  

Any ideas what is causing this?
Spanning tree and working production environment.

Greetings, my work place has spanning tree and I have limited experience with Spanning tree.  I was charged with setting up new Wireless controllers and to route internet only traffic through a specific "Internet Only" VLan.  I have setup the configuration how the vendor suggested.  Basically:

- Create DHCP scope and assign the DHCP Gateway to a VLAN on the controller (created for the Guest VLan).  
- Then create a Vlan for Internet Only and assign an IP address to that VLAN(From the DHCP Scope).  
- Then assign that Internet Only VLAN to an available untagged port on the Wireless Controller.
- The assign an available IP address from the Internet only VLAN on teh wireless controller.
- Then connect that port (0/0/3) to the Internet Only VLAN with its own separate connection.

The problem, is that the Wireless controller is showing that port 0/0/3 is blocking.  Port 0/0/3 is the port connected to the Internet Only VLan.

Port Status
Slot-Port  PortType  AdminState  OperState  PoE  Trusted  SpanningTree  PortMode  Speed   Duplex  PortError
---------  --------  ----------  ---------  ---  -------  ------------  --------  -----   ------  ---------
0/0/0      GE        Enabled     Down       N/A  Yes      Disabled      Trunk     Auto    Auto    -
0/0/1      GE        Enabled     Up         N/A  Yes      Forwarding    Trunk     1 Gbps  Full    -
0/0/3      GE        Enabled     Up         N/A  Yes  …
I have two 3750 switches that are connected and working but here is my only issues. By the way I am very new to networking so please excuse me being naïve .

My issue is when I have a machine on a different subnet other than the main one 10.46.72.x DNS does not resolve even though I manually add and with a DHCP scope that I removed will not work. Can someone please tell me what  am doing wrong. Here is a copy of the config


User Access Verification

Base-sw1>show running
Base-sw1#sh ru
Base-sw1#sh running-config
Building configuration...

Current configuration : 3753 bytes
version 12.2
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
hostname Base-sw1
enable secret 5 $1$lwLf$CJoNDGBl4Ck6AAm/woBVM0
enable password secret cisco
no aaa new-model
switch 6 provision ws-c3750g-24ts
system mtu routing 1500
ip subnet-zero
ip routing
no file verify auto
spanning-tree mode pvst
spanning-tree extend system-id
vlan internal allocation policy ascending
interface GigabitEthernet6/0/1
 switchport trunk encapsulation dot1q
 switchport mode trunk
interface GigabitEthernet6/0/2
 switchport trunk encapsulation dot1q
 switchport mode trunk
interface GigabitEthernet6/0/3
 switchport trunk encapsulation dot1q
 switchport mode trunk
interface GigabitEthernet6/0/4
 switchport trunk encapsulation dot1q…
We are running 2 DCs which are 2008 R2. I know we will be replacing them in the next month or so.. lol
But for now we are seeing an issue with DHCP in that there are different computers that are getting the same IP address handed to them for some reason. Nothing has really changed in the DHCP setup that has been in place for sometime now.
We are seeing this more and more frequent for some reason.
Is there something that I need to check with dhcp to stop this from occurring?
We have a user that works at two locations. He is running Windows 10.
At location 1 he has DHCP with the DNS IP addresses he needs.
At location 2 we need to manually set static DNS for him to access some crucial applications.
We don't just leave the static DNS IPs on because this affects his normal internet access when at home or elsewhere.

I would would like to setup two command files (.CMD) that will change the DNS settings for his NIC per location.
 - Command file 1 - DHCP DNS
 - Command file 2 - Static DNS

What command line can I use to do this?

EDUCATIONAL QUESTION: I need to gain some knowledge our of necessity. Here is the situation. I do NOT know my way around things such as: 1. What the function of DHCP is; 2. Why port forwarding is necessary in some instances; 3. How to configure the ip addresses of my surveillance cameras; 4. How to start anew with my NVR and surveillance system.

I did not want to take the time to educate myself on these items since I would seldom have need for this knowledge. However, since I just got a new fiber isp and virtually nothing operates properly on the surveillance system I think that I must gain the knowledge necessary to do this myself. The company I purchased 70% of the system from will assist me somewhat but refuses to assist in any way at all for the cameras that I did not purchase from them. There are many free utility programs available that I have  installed, however I need the knowledge to determine what to do with them. I think you get the picture. What my question is: Can any Expert advise me of an online course that will teach me what I need to know to understand this area of technology that will not take me overboard? I will not be doing this for a living. I just need to know what is needed to enable me to restore my system to default and start anew and KNOW what I am doing. I wish I didn't have to take the time needed to learn this, but I cannot locate a person that can guide me through all that is necessary to get things up and operating again. I would feel …
In networking how does a computer get an IP address from a Windows DHCP server?  
Do you have to configure the main firewall/router to point clients to the Windows DHCP server usually?
I am having an issue where computers at my DR site are getting DHCP leases from a subnet on a separate VLAN (Though sometimes they pull the correct address). The server the computer shows the lease coming from is a server at my HQ and of course when the client gets the address it is isolated on the network and cannot access anything.

In my environment I have 2 domain controllers configured to handle DHCP. One server is at my primary site and handles DHCP for multiple VLANs at that location. The second server is setup at my DR site and handles only the DHCP leases for the DR site VLAN. I use Juniper switches and have setup the “IP Helper” address for the DR site VLAN to the address for the DR site domain controller.

I have the VLAN for my servers spanning across the 2 sites, so that when we have a failover situation I only need to change the gateways on my servers. So both the domain controllers that handle DHCP are in the same VLAN/Subnet.

All that being said, my phones at the site (which are on the same vlan as the PC’s) do not seem to exhibit the same behavior. They seem to consistently get the correct DHCP server and subnet lease.

To make things worse, I have had 3-4 instances where a machine at my HQ has randomly grabbed a DHCP lease from the DR site server. When I released and renewed the IP on the machines at HQ it quickly grabbed the correct address. However with the machines at the DR site the release/renew typically does no good.
We are upgrading our SBS 2011 to Server 2016, we are migrating both domain and exchange server. After going through some articles on web we have planned to do migration to 2 servers one for domain and dhcp and second for MS Exchange 2016. Our questions are

1. which server should we migrate over first.
2. when we migrate exchange do we require to do reconnections on the all desktops or the outlook would pick it up itself, we have outlook 2010 - 16
It is a Server 2019 Standard install. Two Questions:

1) Which server should be the DHCP server? The VMHost or the DC?
2) I thought best practices said you should not have two partitions ( a C and a D) on one virtual disk. So I created this VM with one fixed 250GB VD. Now I want to add a D: drive using a seperate VD. Can't find out how to do it.






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).