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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If we were to setup two 2012 DHCP servers as a hot-standby scenario (see article below) we would also have to point the Cisco switch IP helper address to both servers and then both would get the unicast or broadcast message through the switch when a client (desktop) looks for an IP, because if we do not then the standby DHCP would never be notified of address needs when the active one goes down. However, if we do then what mechanism is in place to prevent both DHCP servers from replying? Would they consult each other first or how would that work, because if they both reply then it isn't standby, but rather load balancing which is not what we need. Pretty sure someone has tried this and made it work. As always very much appreciating all insights and time. Cheers
https://community.cisco.com/t5/other-network-architecture/multiple-ip-helper-address-on-a-single-interface/td-p/404497
http://thesolving.com/server-room/how-to-configure-dhcp-failover-on-windows-server-2012-r2/
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I bring my (Windows 10 Pro) laptop around to do support in a few different networks - some with DHCP and some where a fixed IP-address is needed. Have tried to find a way to make shortcuts to set the fixed addresses (or set the network adapter back to dhcp), but haven't found a way to do it. Thinking of commands in a batch-file. Any suggestions?

-Olaf-
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I am managing two separate locations, both have a single 2008 R2 DNS/DHCP server and they both hold the FSMO roles. I want to create a secondary DNS/DHCP server at each location for redundancy. Here is where my problem lies, I have 2 servers running server 2012 R2 to use as the secondary. I have had no issues setting up redundant DNS with the 2008 and 2012 boxes. I've hit a roadblock with DHCP and i'm not liking what Google has to say.

Ideally i'd like to run a DHCP hot standby with the 2012 box. Load balance is an option as well if needed. One site would have no issues running a split scope as i only have ~60 devices. The other location has almost 200 devices, a split scope would be difficult to pull off.

I cannot upgrade the 2008 r2 boxes but i can downgrade the 2012 r2 boxes to 2008 r2.

Any thoughts or ideas would be appreciated.

Thanks,

Tom
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Hello,
I need to run a PXE environment, which is working with ThinStation, but i only want specifiied computers to load the PXE. Is there a way of doing that with DHCP reservations on Win2012r2?

Thanks,
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Hi All,

I need some assistance setting up the below. I've got 3 "subnets" to set up internally. All must be able to reach the internet through the suppliers router.

The networks are 2x /26 and 1x /27. VLANS 601 & 603 are desktop pc's. VLAN 602 will be Cisco phones. 601 and 603 do not need any seperation, they're just to cover the seperate DHCP ranges. DHCP will be provided by an external source (hopefully) through a VPN setup on the ASA Firewall. I'm looking to setup outside interface, inside interface and access for all vlans.

Is anyone able to provide a sample config on how I could get this working?

Network Overview
Thanks,

J
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I am having issues with my DHCP server having BAD_ADDRESS entries for a large number of addresses.  The Unique ID ends to be the reverse of the IP address in hex form. I have Conflict detection attempts set to 2.  It is only happening on the Scope attached to the secured wireless.  It seems to be about one bad address per minute or so. I've looked at the event logs on that server that I can find and there aren't any that match the time for the Lease.  Any troubleshooting tips?
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Hello Everyone,

Need to dig up an old issue briefly. The last time I tried to migrate a DHCP scope to an existing DHCP server (authorized and servicing scopes, but not in the same range as the ones being migrated over) I got an error “Error while importing option 6. This option conflicts with the existing option". Apparently this is the case because the already existing server added the entries for 006 DNS Server and 015 DNS Domain Name when it was installed/authorized. At the time the best recommendation I could find was to delete those two entries from the DHCP server options and then run the import (obviously DHCP scope would be exported from the source server) again. The last time I got around it because I had a server we could move the DHCP to that never had DHCP before and thus no previous entries existed. This time I have to move it to an existing DHCP server. However, I would like to understand what is the risk of deleting those two entries and has anyone ever done that step?

The other option would be to export only the v4 aspect of the scope since (as far as I understand it) the option for exporting specific scopes is split into v4 and v6 subcommands. So running something like this: netsh dhcp server v4 export c:\dhcp "192.168.1.0" might work because including the v4 portion of the command allows for the export of a single scope.  This also gets around the "class conflicts with an existing class" error message that is returned when you try to import an entire …
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Hi Experts,

I recently purchased a new MacBook Air for myself so my knowledge of how to configure things in it is pretty elementary, if non-existent.

Hours of scouring the web reading articles and watching YouTube help videos have enabled me to successfully connect my MacBook Air to the shared folders on my Windows 10 Pro machine,

My problem is that I can only access my MAC from the Window 10 machine by the MAC's IP address, which is assigned by DHCP so will eventually change. I don't want to make it a static IP unless there is absolutely no other way around it.

When I go to Networks on my Win 10 Pro machine, the MacBook Air does not appear as a computer to select. Nor does it's IP address. I need to manually access it by \\192.168.1.xxx

I can ping the MAC's IP address, but not its machine name. I can see my own Windows 10 Pro machine appear in Network (File Explorer) though, just not the MAC. I can also access the shared folders on the MAC when I access it using the IP address.

Things tried to resolve so far:
  • Set the "Function Discovery Provider Host" Service to Automatic Start (Delayed) and made sure it is running
  • Set the "Function Discovery Resource Publication" Service to Automatic Start (Delayed) and made sure it is running
  • Temporarily Disabled Firewalls on both MAC and Windows computers - made no difference
  • Have done an "ipconfig /flushdns" on the Windows machine - made no difference
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I dont have too much experience with VLAN Tagging so need a little help,  I have a Draytek Router and a Draytek AP, I have setup a Wifi Network for Staff which goes through LAN1 which works fine through both the Router and AP, I've then got a Guest Wifi network through LAN2 using a VLAN Tag of 10 which ive set on both the router and AP, the problem is there is a Netgear Smart Switch in between which I think is stopping the tagged traffic and I'm not sure how I need to setup the Netgear to allow the traffic, the guest network works fine on the Router but not on the AP the devie thats connected cant get an IP address from the DHCP Server (Draytek Router),  The router and AP are setup as follows: (Just in case you cant open the link I've also put pictures from the guide as you need a login to see the page)

https://www.draytek.co.uk/support/guides/kb-wireless-guestnetwork-ap
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Hi
We have Ruckus wireless network and I have 2 working  SSID.
SSID-A is on VLAN 81
SSID-B is on VLAN 82

My predecessors had setup a NEW SSID which is on VLAN 83  and it is not working.
When I connect my laptop to SSID-A or SSID-B it gives the IP address from that particular subnet.

If I connect my laptop to the NEWSSID, it says limited activity with yellow exclamation mark and gives APIPA 169.254.65.204 IP address.
There is a trouble shooting option with the Ruckus wireless controller using a mac address of the laptop and when testing the DHCP request fails and It looks like the NEW SSID is not set up properly to reach the DHCP server.

So our edge switches are POE Cisco switches and I would like to see the edge switches if they are set with DHCP helper address for VLAN 83
Please let me know the cisco command to view the VLAN configuration of VLAN 83 .
Or let me know if there is any better way of trouble shooting this issue.

Thanks and any help will be great.
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SCCM 2012, PXE boot stops working. I have SCCM version 1806.
The contact with DHCP gets the IP address, next download WDSNBP from my SCCM server.  Everything looks working fine until I got the line "Press F12 for network service boot".
 if I press F12 I got this error: " The Windows Boot Configuration Data (BCD) file from the PXE server does not contain a valid operating system entry. Ensure that the server has boot images installed for this architecture. Error code:0x0000098"
Else the computer skips the image mode and goes to Windows.
WDS has this error "The PXE server processed a request from a client of architecture x86x64.  However, there were no boot images installed for this architecture.  PXE clients of this architecture will not be able to complete the boot process successfully.  To resolve this problem, add at least one boot image for this architecture."
If I use a DVD with the boot image the image process goes through without problems.
Things that I tested:
1-Disable PXE support on Distribution points waits for the server to remove the files, reboot and re-enable PXE again.
2-Create a new boot image.
3-Create a new task sequence.
4-Remove support for unknown computers.
SmartSelect_20180828-093032_Photos.jpg
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Hello :-)

I have only one DHCP scope with the following settings, it was executed by the previous IT staff:

001.PNG
I need to create a new scope with these settings:

Network: 10.61.10.0
Mask: 255.255.255.0
Gateway: 10.61.10.1
Range: 10.61.10.1 -> 10.61.10.254
Name: Vlan_Wifi

But I receive this error:

002.PNG
What is wrong?? :-(
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Im facing very weird issue in my network. Out of the sudden 2 windows 10 PC doesn't have internet, it has valid IP address and can't even ping default gateway or anything else on the network.

But while I was searching around for the fix, I found article where it specified to change MAC address under the network properties to make it work and as soon as I changed the MAC address I got the internet back.

Now could someone, please let me know what could be the issue with original MAC address ?? Or this something ???

I have tried everything I can, update the drivers for network adapter, uninstall and installed the adapter etc

BTW, we are using the meraki MX  84 as my firewall/Default Gateway and I did opened case with them and they were unable to solve it to. One unmanaged switch between PC and Firewall, no AD or DC. PC are on workgroup. NO traffic shaping policy on firewall.

Please share your thoughts..... Thanks !!!
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All expert, I need help to setup ACL for two VLANs, vlan 1 and vlan 20 (guest). DHCP is on vlan 1 that i need vlan 20 to access but block all other traffic. I just want vlan 20 to access Internet connection such as port 80 and 443.  Can you helps me on this? Thank you on advance.
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I have a Draytek 2960 router and two servers; one SBS2011 (192.168.10.5) and one Windows 2016 Essentials (192.168.5.5).
I'm in the process of migrating from SBS2011 to Windows 2016 after which the SBS2011 server will be retired.
During the migration I would like both servers online. The SBS2011 is running DNS and DHCP and the Windows 2016 is just running DNS (DHCP is not installed yet).

I am attempting to configure VLANS on the Draytek, and although all seems sort of OK I'm getting dropouts and poor response when the Windows 2016 server is connected and ports 2,3 and 4 are enabled so I conclude there must be some traffic conflict going on.
My Draytek settings are:
Switch.png
General.png
My intention is that I'm using port 1 for the SBS2011 server and ports 2,3 and 4 for the Windows 2016 (iDRAC, Windows NIC and a single PC on the new domain) so I'm not intending to use VLAN Tagging - I want it all to be physical port based config.
I've achieved a similar configuration on another site but that was using a Draytek 2862N and that worked fine.

Not sure what's going on with this.
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It is a SBS-2011 Server. I will create a new DHCP reservation and set the reservation name to "GSMPC-11 N". Then it looks like when it goes active Windows changes the name to the computername.domain i.e. gsmpc-11.gsmetalinc.com

   Well..... what is the point in even creating a reservation name when Windows changes it to computername.domain automatically? Is there any way to stop it from changing the reservation name?
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Hello,
I have DHCP failover cluster configured (hot standby mode) and its not functioning good.
Sometimes workstations need to restart to pick up IP address.
So,I plan to remove second(standby)dhcp host and remain only one dhcp server
Is this what I need to do?Delete dhcp failover and unauthorize stand by dhcp host?Scope remains?
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Hello Experts,

I want to test DC site failure between 2 sites connected via a leased line. Both sites have 2 dcs each on Win server 2008. Both sites can communicate with each through our leased line.
Both sites have their own DNS and DHCP servers.  

The plan is to unplug both DC on one site and see if those on the other site take over and vice versa. This will simulate a complete DC site failure.

As I understand we will have to move our fsmo's role over to the active dcs when the others are taken down and also DHCP and DNS. If we did have a complete site DC failure on site1 I can I setup a DHCP and DNS in a disabled state in site2 ready to take over in case of an emergency.
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One of our client has a strange issue with migrated DHCP. They are getting BAD_IP address issued by DHCP.
Basically they exported the old DHCP and imported to new DHCP server.
Any help would be appreciated.
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Is it Enough to configure DHCP Snooping without ARP Inspection

I would like to know if it is efficient to configure just DHCP Snooping and do not configure ARP Inspection.
 I thought DHCP snooping is enough to avoid having Rogue DHCP in the Network. So what  else that ARP Inspection adds to the DHCP Snooping ?

Thank you
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I recently split our DHCP addresses between to DHCP servers.  One server has a scope of the first 127 addresses (1-127) of a network, and the other server has the remainder (128-253).  Things appeared to be working well.  Both servers lease addresses in the proper ranges, and I can ping them.  However, on two clients that host web interfaces for various programs, the web interface will not open.  They do open on the localhost.  Are there any ideas about what could be causing this?  I believe both of the clients in question have the proper DNS entries.  However, one client is set to get its address by DHCP and is assigned a reservation.  The other client has a static address.  I have added A and PTR records for both.
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Had to reboot a ESXi 5.5 server.  It decided that it wanted to pull an DHCP ipv4 address.  When trying to set it back to static. it tosses out an error that it cant save it because of iPv6.  We have that disabled.  It can pull a DHCP address no issue.  Never seen this before.  Where do i start?  

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Dear Experts
Installed windows 2016 standard and configured it to function as domain controller, DNS server and DHCP.  It is observed the after promoting the server to AD domain controller the IP of the serer in the primary dns changed to local host I mean pointing to 127.0.0.1, manually changed to the actual IP.
While creating the forward and reverse zone had selected “do not update dynamic updates”
Following are the issues faced
1.      While joining the client system that is windows 10 pro to domain it accepted to join but message shown “preferred dns could not be changed” and then after reboot able to login with domain user. Please let me know where I am going wrong
2.      When the user logon and click on network browse the domain controller can see netlogon directory but does not show the user home directory, please let me know what I have missed.
3.      I made the normal user a member of domain administrator group in the server and then logon to the client system with this user but he does not get admin privileges when click on network to change IP address it prompts for logon and password but it does not allow administrator login to client system nor it does not consider this user as administrator who is actually member of domain admin group  
4.      Before joining the client system to the domain controller is required to create A and PTR records manually and then after join the system to domain
Please help me understand and suggest the steps to resolve the above 1 to 4, this…
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We have be experiencing issues with the DNS servers that are being setup on DHCP clients. We have recently setup and configured Cisco Umbrella. The VA's have been setup and all DHCP scopes have been updated to use the VA's for DNS. All was working well or so it seemed but we started noticing DNS issues. ipconfig sometimes shows the correct DNS servers (the VA's) and sometimes shows the internal DNS server. The DNS servers change in between lease changes. Any advice on troubleshooting would be greatly appreciated.

Regards,
ABBEadmin
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I've setup a Server2016 test environment. Contains a VPN server, NPS Server and a DC. I connect to the VPN fine. Pulls an IP from the defined DHCP scope. I can ping any internal resource, but i cannot navigate to any shares. I've gone as far as completely shutting off the windows firewall on the  server and workstation(Win10) sides, still cannot navigate to a any shared folders on any of the 3 servers. Ive made sure the DNS entries are there. Any ideas as to why i cannot browse to the server by IP?

EX. from an external network connected to the VPN
ping 192.168.17.50 - get 4 responses
ping testdomain (DC server name) - Could not find host testdomain
nslookup 192.168.17.50 - Server: testdomain.test.local
                                           Address:  192.168.17.50
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DHCP

10K

Solutions

14K

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).