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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).

Hi Experts,

after DHCP migration, all WIFI clients do not get any IP.
But over LAN it works.

Here is the error:

PTR record registration for IPv4 address [[172.23.22.111]] and FQDN PC1-NB001.wittur.com failed with error 9005 (DNS operation refused.
).

Open in new window


The DHCP is not on DC.
It is installed on another server.

Any ideas ?
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Hi Experts,

I like to migrate my DHCP config to another server.
The old config is on Server 2012 R2
And my new Server is Windows 2019 Core.

Is this possible ?
Please can you show me the commands ?
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I picked up a couple of the new Linksys Business APs that allow VLAN Tagging and I am having fits getting the VLANS on the switch configured properly to get these APs to work. There are currently 3 VLANS on the switch:

1: Management, ports 1-28, port 1 goes to SonicWall
2: Guest, ports 29-34, port 29 goes to SonicWall
3: Printers, ports 35-44, port 35 goes to SonicWall

Each port on the SonicWall is a different network and does the rules between networks. It is also the DHCP for each network. So... what I was trying to do was put these APs on the Guest network and if I were to tag a specific SSID with VLAN 3 it would give the clients on that SSID access to printers.

So what D-Link told me to do was to tag port 35 and share it with the Guest VLAN. So when a client on that specific SSID (tagged with VLAN 3) came in to VLAN 2 it would immediately pass the packet to VLAN 3 and in turn give it access to printers.

When I did that the management VLAN could no longer avvess printer. What a mess. It seemed so simple. Any ideas on what I am missing?
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I have a windows server 2012R2 for DHCP and DNS.

I am reviewing my reverse lookup zones in my DNS server and I have a lot of computers in there with the same name, but with different IPs.
What is the best way to clean it up?  Can I just delete every entry for every reverse lookup zone?
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Went on a call to a new client today, who has been having issues with their network.  They have a DSL modem with WiFi on channel 1 (Since disabled) cascading to a TP-LINK Archer c5400 (Upgraded firmware today).  They are working on getting the PPPoE (Centurylink DSL connection) so we can bridge the DSL modem and set the router up properly.  Some devices hardwired and wireless will not function because they are getting a DHCP address from the DSL modem.  I can log into the DSL modem on those computers.  Is this a malfunction in the TP-Link (It only happens less than 10% of the time and very random on devices)?  I have had very bad experiences with TP-Link switches, are their routers any better?  The owner said the problems have always been existant and the old IT company (who installed it), could never get it working 100%.  I am recommending replacement of router, but wanted to hear thoughts on this subject.  The client will be ordering their own new router, and won't have until Monday.  This should be a non-issue once the modem is bridged.

If I release the DHCP enough times, it will go back to the correct DHCP server of the router and start working properly.  The DSL modem is not accessible by devices connected when getting the working IP address.
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I'm experiencing a new crazy issue.  I have about 9 MAC computers on a network with mostly Windows PCs.  I have a windows 2012R2 DC, with AD, DNS, DHCP, etc...
If the Macs use a static IP, everything works fine, the hostname stays what is configured by the user.

As soon as I change the manual IP to DHCP on the MAC, after a reboot, the hostname of the PC randomly changes to a windows PC name.
It's completly random, as different MACs use different windows PC names.   Where do I even begin to troubleshoot this issue.

I am running different versions of the mac, on most of the macs, i'm running Mojave.  A few are running Catalina.
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Dear Experts
We recently decided to implement MPLS connectivity between two locations, the location 1 head office which has ILL (leased line) Cisco FTD on Fire pro 1010 with cisco FMC appliance.
Since it is managed MPLS connectivity service provider has placed their router equipment in both the locations in that port 0 they have connected it to their modem and port 1 we are thinking to connect with ethernet cable to our switchs at  
At branch office
Please suggest at branch location port 1 of the service provider router equipment will be connected to the local switch and same router we have asked to the configure as DHCP server.
At head office
We have connected service provider router to local switch making use of port 1 but here we have windows AD functioning as DNS and DHCP hence service provider router is not configured to function as DHCP server.
1.      Please suggest should the MPLS router to be connected to firewall (CISCO FTD) or is it okay to connect directly to our local switch
2.      Since we are in MPLS network can we think to configure DHCP slave at branch location OR dhcp primary server
3.  please suggest is it recommend to have RODC in branch office, we prefer to join the systems of branch office to domain (windows AD) which is in head office

Branch location IP pool is 192.168.105.0/24 and head office IP pool is 192.168.109.0/24
please help on above 1 , 2 and 3 suggest the best practice design, thanks in advance.
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New Lenovo Thinkpad laptop with Win10 Pro v1909 connected WIRELESSLY to a home office peer network.

Laptop connected to a NAS and a Unix server with no difficulty, but couldn't connect to any printers. One printer is an HP LaserJet with a static IP address. The other is a is a shared HP USB connected inkjet printer.

Neither printer's installer could see the target printer. The LaserJet was neither pingable nor could I connect to its webserver with a browser.

An older Windows 7 laptop, also connected wirelessly, has no difficulty printing to either of the printers.

The laptop gets it's IP address via DHCP. It's on the same network as all the other devices on, hence its ability to connect to the NAS and the UNIX server.

It's been driving me nuts...then I wa finally able to connect it to the network with a wire. Presto...both printers installed as expected. Went back to a wireless connection and the printers were unreachable again, as expected.

Why? ALL network properties for both the wireless and ethernet adapters are exactly the same. Network and Sharing options all all the same on a Private network.

What am I missing?

Thanks
Mark
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We have a PC that we have staged with Windows10 pro and enabled Hyper-V
We have set up a Windows10pro VM
The physical host has two network cards.
One set via DHCP
One set with a static IP

There is an application that will run on the VM that needs to communicate with the static IP network card.  
Everything else on the VM can/should go through the DHCP assigned network card.

I've done some sleuthing around the internet, but cannot find or decipher how to achieve this in the network settings of the HyperV.

Any help is greatly appreciated.
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Hi guy,
I'm configuring a cisco switch (slm2024).
This is what i want to do:

port 5 -> VLAN 10 (LAN)
port 12 -> VLAN 5 (WAN)

On port 12 is connected a ISP modem/router. This router provide a DHCP of private class (192.168.0.X/24)

On port 5 is connected a laptop
I don't understand why laptop is getting a IP from DHCP...it's in a different vlan!
Maybe this issue from vlan1?

This is config

vlan1.PNG
vlan5.PNG
vlan10.PNG
Thanks!
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DNS and DHCP Interaction

Recently we had to replace old  computers with new ones but we kept the same hostname , the new computers get different IP address than the old ones from DHCP.

Example :

Old ComputerA  replaced and named  the same ComputerA
Old ComputerA IP address: 10.10.10.10
New ComputerA IP address: 20.20.20.20

What I have noticed after replacement:
If I login locally to New ComputerA, and run Ipconfig, I will see 20.20.20.20  which is correct.
If Remotely I ping by hostname the ComputerA,  I get 10.10.10.10 with Destination Host Unreachable. [you can see it looks for old IP address]
if Remotely I ping Reverse lookup : Ping -a 20.20.20.20 , it will Reply properly and shows ComputerA  with IP 20.20.20.20


So the problem seems to be the DNS A record does not get update quickly,  I said Quickly because after sometime, if I go and ping by hostname ,ie : Ping ComputerA, I get a proper Reply with 20.20.20.20

My question is I do not understand why Reverse Ping [Ping -a <IP address>] will Reply quickly and Ping Hostname did not Reply until later time....

Any clarification will be very much appreciated.

Thank you
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Hi Experts,

we have an in ternatinal network.
Do you know a way, how to determine all my DHCP servers in the whole network ?
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I am currently investigating on migrating from our current Windows 2012 R2 DHCP and IPAM setup to Windows Server 2019.
A few questions?

Will DHCP 2019 work with existing IPAM server on Windows 2012 R2 or will I need a separate Windows 2019 IPAM server?

If I need a new IPAM server can I have it along side the existing IPAM 2012 server or do I need to migrate or upgrade it?
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Our wireless vendor is currently telling us that the DHCP IP addressed assigned to one of our meshed Access Points is in conflict with another device on the same network with a specific MAC address.   We have looked in DHCP and DNS on our Domain controller and have been unable to locate this specific MAC linked to this IP From the ARP table they provided us.  

Can anyone tell me a command I can run that can show me the MAC and IP along with the device name the arp table reports on the wireless Access Point so I can try and delete it?   This is causing a severe conflict.

(192.10.10.82) at f4:ea:67:7c:b2:23 [ether] on eth0 <--- Not AP1
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My company has two physical locations each with its own server running AD DS, DNS, DHCP and their own unique databases.   All workstations in both locations run identical applications.    Location A will be shutting down for a couple of months for renovations.   I would like to move server A  to location B so its database can be accessed.   I was planning on giving server A a DHCP scope of 10-130, while configuring server B a scope of 130-250 all under the same 192.168.1.xxx.    Server A (Windows Server 2008 R2) would have an address of 192.168.1.2 while server B (Windows Server 2016 Standard) would be 192.168.1.3.

Would the 20 workstations at location B be able to switch back and forth between Domain A and Domain B simple by logging out of A and into B?

If this theory is not correct, what is the proper way of setting this up?
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I just upgrade from ESX 4.5 to 6.7 and the controller can not longer see the access points. There have been some changes in ESX for the interfaces, but for some reason it is not working. (I can see one new difference is that the switch and the port can be configured for Promiscuous mode, I tried both but neither work)

Virtual Switch:
1. Allow promiscuous mode Yes
2. Allow forged transmits Yes
3. Allow MAC changes      Yes

Data Port:
1. VLAN ID: 4095
2. Allow promiscuous mode Yes
3. Allow forged transmits Yes
4. Allow MAC changes Yes

Service Port
1. VLAN ID: 0
2. Allow promiscuous mode No
3. Allow forged transmits No
4. Allow MAC changes No

Switch Config:
interface GigabitEthernet0/1
 description trunked port
 switchport trunk native vlan 30
 switchport trunk allowed vlan 21,30,31,40,41
 switchport mode trunk
 spanning-tree bpdufilter enable
 ip dhcp snooping trust
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An easy one for some Expert, which has encountered this issue before.

Time has come to update a 2008 R2 Active Directory environment which consists of 4 Domain Controllers (why four I have no idea, it's a small environment for 40 users!)

They have 4 DCS, 3 DNS servers (again 2 would be fine!), 1 DHCP server, all DCs are just DCS no file and print, so they just do the roles of DCs.

and to add everything is working well, replicating at present, no need to do anything really other than End of Support next year!

As 2008 R2 support comes to and end next year Jan 2020, a good time to get update to the latest Server 2019....

What I want to do is to remove 2 DCS, to get to two working DCs, and then add two new 2019 DCs and transfer roles.....

BUT......there is a issue dcpromo and demoting DCs....

and I know I can mangle AD jusing adsiedit and force remove (dcpromo /forceremoval, but I would really like to do this cleanly...so this question.....) I'm not sure how this legacy issue will affect us in the future carry on reading,....

Four DCS called DC1, DC2, DC3 and DC5 (DC4 was removed correctly 8 years ago because it failed! - I did it properly!).

If I use the dcpromo on DC5 it gives and error...


Active Directory Domain Controller Removal (2008 R2 Server) - The correct method.
This error is given on DC5 and DC3.

I've done some digging and it looks like a server was not removed correctly many years ago called EMILY! This was many years ago, because inplace upgrades have been done for years....since 2000!
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I have a problem with network access.  Running a network which has four servers, 5 workstations, and a VPN. Suddenly we have lost the ability to access one of the windows 7 servers.  One of the other servers provides DHCP for the local network so the network is still running.

Of course this server holds holds our order entry DB and the CAD file archives.  The server is running windows 7, and RAID.   I can access all files from the server itself.  I also can access other systems from this server.  

All of the other systems have the appropriate server files mapped as a network drives, which they can no longer access.

I have checked the settings, but I thought I would throw it out there to see If I have missed anything before I replace the system.
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Please see the attached (pardon my scratch!) pdf document of what I'm looking to do. The main reason for my decision to use PFSense is because my Meraki gear maxes out on the WAN side at 250Mbps. I now have a 1GB up/down and a 100/100 secondary circuit. I know that if I use gb cards on a pfsense system, I should get awfully close to 900 Mbps. Very new to pfsense, so the more help the better. :)IMG_0001.pdf
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Greetings,

Newbie to VLANS here and I have a "lab" setup that I'm working with prior to an installation that will benefit from VLAN Topology.  Here's the basics of the test environment.

Internet--->ZyWALL USG20 Firewall--->Cisco 2960G Switch--->Computer

ZyWALL IP is 10.1.1.1/24 with DHCP Active
Switch IP is 10.1.1.254

Management of both devices work fine as does Internet access on Native VLAN1

Steps done to create VLANS:
On ZyWALL
-Create two Zones for VLANS
-Create VLAN10 and VLAN20, both using LAN1 as "base"
-VLAN10 ip is 10.10.1.1 with DHCP server active starting with 10.10.1.50
-VLAN20 ip is 10.20.1.1 with DHCP server active starting with 10.20.1.50
-Created Policy (rule) for VLAN10 and VLAN20 zones to access the WAN
-Connect LAN1 port on ZyWALL to Gi0/1 on switch.

On Switch
-Create VLAN10 and VLAN20 on switch; VLAN1 (default) exists as well
-Set Gi0/1 to 801.2Q Trunk with "ALL" VLANS included
-Set Gi0/9 to VLAN10/STATIC ACCESS
-Set Gi0/11 to VLAN20/STATIC ACCESS

Any connections on VLAN1 (default) work as expected.  DHCP, DNS, Internet all good

Connecting a computer to Gi0/9 (VLAN10) results in the computer using 169.X.X.X address on the nic, HOWEVER, in the ZyWALL DHCP logs there are entries reading
"DHCP offered 10.10.1.50 to <COMPUTERNAME(MACADDRESS)>"
Same result for Gi0/11 (VLAN20)

Obviously I'm missing something in the config on the server or swtich, because the computer is asking for an address, the DHCP server is handing …
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I am trying to remove the DHCP Server role on SBS 2008, hangs on "Initializing removal" step.
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The ISP I use, xFinity, charges $100/month (arm and a leg) to provide me with a static IP for my home Windows network, specifically a domain controller.  I'm wondering if there's a workaround.  Could I connect a switch to their router that would function as a DHCP server and serve out a static IP address to my Windows domain controller?  Bottom line?  I'm trying to save $$$.
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Hi,

I am trying to setup Hot standby DHCP server2012 (two DHCP server with multi-scope)
192.168.0.0
192.168.1.0
192.168.2.0
I am using two servers with fail-over DHCP configuration. (Hot standby) with IP address
192.168.0.1 for server 1 and 192.168.0.2 for server 2

In the Cisco 3750 switch I created 3 vlans
Vlan 10 with an IP address 192.168.0.3
Vlan 20  with an IP address 192.168.1.1
Vlan 30  with an IP address 192.168.2.1

In the configuration I added IP helper-address command to refer DHCP servers
Under each Vlan interface I added two IP helper address

Under Vlan 10
ip helper-address 192.168.0.1
ip helper-address 192.168.0.2

And so on for Vlan 20 and Vlan 30

The computers work fine and got IP address and getaway for each Vlan. However, I tried to test the fail-over DHCP and I shut down the DHCP server with an IP address 192.168.0.1 and waited to get computer an IP from second DHCP server but it's not working. I Release and renew IP and nothing changed.

Is there any missing part of my configuration?

Thanks
0
I have a customer that recently rebuild their DHCP, they had a /24 subnet and now they are /16 they have around 300 devices registered and everything for the most part is working fine, but I have a a blue alert on the DHCP and I dig into the properties of the LAN I see that start IP Address is 10.11.0.1 and End IP Address is 10.11.254.254.

To my knowledge a blue alert means you're running out or ran out of leases but they should have enough addresses but maybeI'm wrong.

Is this correct ? DHCP Scopes are not my strongest topic I think is ok but I could definitely being wrong.

Any assistance would be really appreciated it.
Annotation-2019-11-25-135402.png
Annotation-2019-11-25-135401.png
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I found some errors running health checks on my domain controllers.  I did not have any problem with users, computers, DNS or DHCP that I notice.
I create a test GPO in DC1 and immediately was in DC2.
I got these errors:
1-      There are warning or error events within the last 24 hours after the SYSVOL has been shared.  Failing SYSVOL replication problems may cause Group Policy problems.
2-     [1] Problem: Missing Expected Value
Base Object: CN=CON-DC1,OU=Domain Controllers,DC=Contosocs,DC=local
Base Object Description: "DC Account Object"
Value Object Attribute Name: msDFSR-ComputerReferenceBL
 Value Object Description: "SYSVOL FRS Member Object"
Recommended Action: See Knowledge Base Article: Q312862
 [2] Problem: Missing Expected Value
 Base Object: CN=CON-DC2,OU=Domain Controllers,DC=Contosocs,DC=local
Base Object Description: "DC Account Object"
Value Object Attribute Name: msDFSR-ComputerReferenceBL
Value Object Description: "SYSVOL FRS Member Object"
Recommended Action: See Knowledge Base Article: Q312862
3-      LDAP Error 0x20 (32) - No Such Object. ......................... CON-DC1 failed test
4      DCOM was unable to communicate with the computer XX.XXX.XXX.111 using any of the configured protocols; requested by PID      390 (C:\Windows\system32\dcdiag.exe).
5-     DCOM was unable to communicate with the computer XX.XXX.XXX.95 using any of the configured protocols; requested by PID     11e8 (C:\Windows\system32\dcdiag.exe).
These IPs related…
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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).

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