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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Hi,

Could someone please explain the practical difference between these two dns settings in DHCP?
DHCP-DNS-config.PNG
I am currently set to "Dynamically update DNS records only if requested by DHCP" but I have read that best practice is to use "Always dynamically update DNS and PTR records"

 Why should I do this? I do see many duplicate/old A records in my DNS. Will changing the setting to "always" stop these duplicate records?
old-duplicate-dns-records.PNG
Thank you very much
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Hello folks, need another pair of eyes to check my DC Win2016 hardware specs.  Only for AD purposes box.  DC, DHCP, DNS.  It'll be sitting separately from VM environment and crunching only AD specific purposes.  

HPE ProLiant DL360 Gen10 Performance - rack-mountable -Xeon Silver 4110 2. - x1
Intel Xeon Silver 4110 / 2.1 GHz processor- x1
HPE SmartMemory - DDR4 - 16 GB - DIMM 288-pin -registered - x1
HPE Read Intensive - solid state drive - 480 GB - SATA 6Gb/s - x2
HPE Foundation Care 24x7 Service - extended service agreement - 3 years - o - x1
Hardware Option(s) Install into a Server (CDW ConfigurationServices) - x1
1
Switchport in an err-disable state due to MAC Adress conflict.

Have cleared the DHCP bindings which cleared the err-disable error, but now have no connectivity.
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Hi

I have two questions regarding our DHCP server.

We have a DC running DHCP  on a server that we will shut down (SERVER 1), and therefore we need to move the DHCP service to another server (SERVER 2), can I just deactivate it on the first server (SERVER 1), and then active it on the other server (SERVER 2)?
Even if I can I have a problem because our active DHCP is configured on all our routers at out ISP who connect our offices as DHCP relay with IP-address x.x.x.x, and therefore I come to my second question, can I after shutting down the old DC (SERVER 1), configure the new DC (SERVER 2) with that old IP address that (SERVER1) had, will that work?
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Hey guys,
 We are considering to provision all our Domain Controllers as CORE edition servers 2016.   Wondering on others experience from manageability standpoint.  
How do you guys manage it.  Say you need ADUC, DNS, DHCP, AD Sites-services, etc, etc.  
I'm thinking to have at least one Regular Domain Controller with GUI interface.  Others are OK to have CORE.  Thoughts?

Thanks in advance.
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Hi everyone,

This may be a DNS issue - maybe not.

I had a user who was encountering some printing problems yesterday.  I got the printing problem solved but in doing so discovered that I was able to ping the PC using two different hostnames, but having only one IP address.  I've verified that the inaccurate hostname belonged to a workstation I've already removed from the network 30-45 days ago.

On a side note, I've since upgraded the OS from WIN 7 to WIN 10.

Now, 24 hours later, I'm still able to ping the one workstation by the two different hostnames.  Is there something else I need to take a look at?  We do have some special vlans that live in our enviornment.  Is it possible that, maybe, the MAC of the PC got assigned on a vlan and is somehow associated to the old PC name - or is that really thin possibility?  Just tossing ideas around.

Thanks.
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What is the reason for multiple BAD_ADDRESS in DHCP?  Description - This address is already in use.  I deleted them already few days back.  They came back for some reason.  About eight of them.
And it seems they show up after a an abrupt power outage we had.  Not sure if related.

Server 2016 Domain Controller.
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I would like to have some confirmation that I setup DNS scavenging correctly on my DNS server.  The DHCP lease duration is set 8 Days.  Under DNS Management, I right-clicked on the server and selected properties.  On the advanced tab, I enabled automatic scavenging of stale records and set the savenging period to 4 days.  I then righ-clicked on the server and selected "Set Aging / Scavenging for All Zones.."  I enabled the the scavenging of stale resource records and set the no-refresh interval to 4 days.  I set the refresh interval to 4 days.  Finally, I right-clicked on my forward lookup zone and selected properties.  I clicked on the Aging button on the general tab.  I enabled scavenging of stale resource records and set the no-refresh and refresh intervals to 4 days each.

Did I miss anything or is this correctly setup?
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My environment consists of a Sophos UTM Firewall, two ESXi Hosts, about 12 Windows Servers running as VMs, some physical switches, physical wifi controller and APs, network printers, and client PCs.  

On my Windows DHCP server, I have the scope defined as 10.20.0.1 thru 10.20.0.254.  I have an IP exclusion range from 10.20.0.1 thru 10.20.0.100.  I currently assign static IP addresses to my Firewall, WiFi controller, Switches and all Servers (running as VMs).  All of these devices and servers are assigned IPs within the 10.20.0.1 thru 10.20.0.100 IP range.  In addition to assigning the devices and servers static IPs, I also create reservations for them within my DHCP server.  

I also create DHCP reservations for my network printers but I leave the printer itself configured to acquire the IP address from the DHCP server.  All of my client PCs, BYOD devices, etc. simply receive an IP address from the DHCP server.  

Is there any problem in creating reservations for my servers and hardware despite the fact that the IP range they fall within is excluded from the scope AND the IP address is physically assigned to the device or server?  I was creating the reservation so that I had quick visibility within the DHCP server as to what server / device had a given IP address.  However, I am not sure if creating these reservations could cause a potential conflict or not.  The one "flaw" that I could see is that if a VM is moved or restored then the virtual NIC would be assigned a …
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rpi3b,  Stretch, used this tutorial for setup:

https://thepi.io/how-to-use-your-raspberry-pi-as-a-wireless-access-point/

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=192.168.173.11/24

Open in new window


ifconfig output on rpi:
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.173.11  netmask 255.255.255.0  broadcast 192.168.173.255
        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 169.254.144.35  netmask 255.255.0.0  broadcast 169.254.255.255
        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 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 260  bytes 22236 (21.7 KiB)
       
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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?
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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.
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Simple WAN - 3 sites, one main and two remote sites connected via a MetroE with Cisco routers.  IP address of cisco router is 192.168.1.253 at a particular site...

Each site has sonicwall to ISP internet.  For this example, sonicwall is 192.168.1.254.  DHCP is handled by sonicwall and default gateway for network is 192.168.1.254.  

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?

Thanks
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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.
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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)

Thanks
0
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.

Thoughts......
1
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?
1
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.
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What is a better design regarding a company wireless network?

At my work we have 2 Guest Wireless Networks.  

1.  Guest Wireless (SSID) (172.20.102.0/24)
2.  BYOD Wireless (SSID) (172.20.103.0/24)

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 …
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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 10.0.3.200
X0 with subnet 10.0.0.1 is a Corporate LAN with DHCP served from Widnows Server 2016 deployed by me with subnet range 10.0.0.xxx to 10.0.0.200

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?
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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)
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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.
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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 192.168.0.1 one port of that runs to the Netgear orbi, The orbi in turn has created its own network on 192.168.1.1, my switch is connected to the orbi with an ip 192.168.1.66.

I have nas connected to the switch, previously it was on 192.168.0.185 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.
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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?
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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  …
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DHCP

10K

Solutions

15K

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).