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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Our DHCP server about every week has been causing us issues. It won't hand out IP addresses to clients. What happens is when I log into the DHCP server and go to task manager I see that the service: svchost.exe is running our CPU at 100%. When I kill the service and it restarts itself the issue is resolved. What is causing this issue? Or what can I look at to see where I can further research this.

Our server is Windows 2008 R2 Standard

When I go into the logs I don't see anything under DHCP to me that stands out.
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I have an SBS 2011 which runs exchange/DNS/DHCP/VPN but I had to remove the DHCP from it and use the routers DHCP for reasons that I cannot explain. Everything works fine but I cannot find anything online that says that VPN will work with an external DHCP.

I've just had my first remote user complain that she cannot connect so I rerun the fix my network and setup the vpn again and she appears to be connected fine. Is there anything else I need to check/do on the server or the router to ensure proper operation of the VPN?
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Hi Experts,

We are moving to a new Mitel Cloud service and have IP485G phones.

I setup a VLAN on our switches along with a DHCP scope on a windows 2012r2 DC.


We receive the correct IP, router, dns  from the VOIP VLAN but the option .156 is not populating in order to get config files and firmware updates.

I am using the string below configServers="update.sky.shoretel.com"  

Thank You
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I have 2 AD-Integrated DNS servers that have been running on the domain for about 5+ years. It's full of old A records and as a result, a single IP address (for example 192.168.0.205) may point to 3 or 4 different computers. I see lots of records with old timestamps (2017, 2016 for example). Although I am tempted, I don't want to assume they are stale (or incorrect) and blindly start deleting A records.

'Scavenge Stale Resource Records' is enabled. No-refresh interval is set to 7 days and the Refresh interval is also set to 7 days. I am assuming the servers are using the default security settings (I am not the one who set them up). Dynamic update is set to 'Secure only'. IPs are assigned using the Microsoft DHCP server on the same domain.

(I am only referring to DNS records added automatically, not static records). So if a computer was decommissioned 3 years ago (for example), why is the A record still there?
What would you recommend as the best way to clean up to non-static A records on this DNS server?
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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
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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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My DC died last week.

So I moved my DHCP to my firewall to have my users work online since all the DATA is now cloud based and the server was really only DHCP and AD.

Current setup now because we needed users to authenticate since their PC's were losing the relationship with the dead server.

I got a PC and installed server 2016 essentials. Installed a NEW domain name which the client wanted to do a while back so took advantage now. All PCs are now joined into the new domain.

We ordered a new Dell poweredge server and  once that comes in we want to make that PDC and the current PC "acting as a server" as secondary.

What OS does the poweredge need to be able to transfer roles from the temp PC server to turn it into a PDC? How do we accomplish this?

Thank you
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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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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?
Or
it will loose the IP since the DHCP is not available to validate ?
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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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We have a printer issue that is having an issue connecting to a network via wifi. We have DHCP setup on our Sonicwall firewall, but we are not using this for the printers, we have setup a range of IPs 192.168.0.2-50) outside of the DHCP scope, to be used specifically for these printers. One of the printers (192.168.0.10) they are not able to print to, nor is it pingable. If we change it to DHCP and it gets another IP, we can print and all is fine. If we assign it another static IP from the range I mentioned above (192.168.0.30) it prints fine as well. There JUST seems to be an issue with this one IP (192.168.0.10) - Like I mentioned, no one else would be getting this IP because it is outside of the DHCP scope, and there is no other device in the building that is statically assigned this IP. Has anyone seen this type of issue? Any suggestions?
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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
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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......
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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?
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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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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).