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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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Dear Experts

We have DHCP server in the LAN please suggest on the following
1. would like to reserve few IP's to few users and we allow only those IP's to access the internal application web based server, please suggest the best practice considering the security controls for the dhcp,
2. is there a way that even though the wifi network password is known to the users still there should be one more level of authentication or some controls only if that is accepted then only  the users device gets IP assigned
please suggest, thanks.
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Win 2016 domain with 2 x DC, 2 x DNS Servers, 2 x DHCP servers, 500 x clients.

DHCP and DNS are linked by the Active Directory.

There are some machines in DNS that have the same IP which is obviously causing name resolution errors. can anyone suggest how I troubleshoot this?

One thing is I have recently changed a DHCP server to a new name, will DNS need to be told about this change?
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in an Active Directory environment, is there any advantage over using Windows DHCP server over any old DHCP service (let's say setting it up on a Linux box or on a Cisco device for instance)?  is it simply a case of using it because it is there?  or is using it a best practice in a Microsoft AD/DNS environment?  reason i'm asking is, we're planning an AD migration to a centralized domain from what we currently have which is a distributed series of AD environments.  there's some debate on whether DHCP should even be included in the scope of the discussions, let alone how it should be implemented.  AD is being centralized, but as a site IT support person, i'm trying to build an argument in favour of my insisting i still have some local management of DHCP (reservations what not).

i guess i'm asking two questions.  1) is Windows DHCP a no-brainer in a fresh or migrated AD environment, and 2) even though i will (in the end) have only OU Admin level access over my local site, is there a way to still allow me DHCP management at my local site?  question 1 is most important to me as i don't know why the Project Managers are treating this aspect of the project lightly.
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Hi Guys

Environment:
Small environment (40 x VMs, Single building)
Cisco 3750 Series Core switch x 2 (24-port) Stacked

We have one IP Helper Address assigned to our Primary Domain Controller for DHCP purposes.
We have a secondary Domain Controller which I have configured to Load Balance IP addresses (50/50 split) for HA. However, this is not going to work as the Core Switch will only see the single IP Helper Address.

How do I add a secondary IP Helper Address on the Core Switch to include the secondary Domain Controller?

In advance thank you for your support.
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Does anyone know why some DHCP entries show blank names?  IP, Lease expiration, MAC address, etc.  Just missing a name.  
Would that be some sort of an appliance/hw that without a hostname assigned?
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Folks, do you know what icons mean on DHCP clients.  Some shows a clock and others some sort of checkmark or strike.

This is for Windows Server 2016
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What's the best way to switch to another DNS in DHCP server?  
Lower lease -
Change scope options 006 DNS Servers  - reboot
Sounds right?

Is there a way to do it transparently without a boot?
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In the DHCP scope options 006 DNS Servers.  
Is it required to put all AD DNS servers there?  I got two in this case.
Also, is it a good idea to put google dns as 3rd option 8.8.8.8 ?
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How does DHCP work with VoIP phones?  Do they phones need to get restarted every time the DHCP lease expires?  Or it works no different than a regular computer client?
For the first time phones need to be booted to obtain IP addresses.  Also when DHCP or DNS server changes.  What about a regular DHCP refresh at the end of the lease duration?
We use Polycom ip phones over poe.
Please advice.
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I am having machine A hostname responding with IP of B. Same user.  And vice-versa.  In DHCP is other way around.
Tried to sudo dhclient, etc.  Restart, nothing helps.
Both ubuntu machines.
What troubleshooting steps take here?
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How to grab list of DHCP scope, reservation details into excel or notepad in windows 2008
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Linux DHCP was able to give out DNS search domains.  Windows doesn't.
Cannot resolve by short names after migrating DHCP to Windows AD Servers 2016.
Option 119 DNS Search List not working.  Even though says it design for non-windows client.  Domain names with semicolon.   Still not resolving.
Group Policy wont work because the clients aren't joined the Domain.  

So the only option to tell the users to use a FQDN (long names) from now on.  Some unhappy.  Oh well.  

Any other options?
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I have a blue exclamation mark on IPv4 in DHCP.  Is that because they aren't configured for failover timing yet?  Do I need to select Automatically update statistics every xx minutes on both DHCP servers?  Active and Standby node?
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I relatively recently demoted one of our two 2008 domain controller, and added a 2016 DC. We'll call them DC1 (2008) and DC2 (2016).

AD, DNS, DHCP (To an extent) have been fine...but I noticed today that nslookup is searching DC1 and returning "Can't find...".

I went into both DC's and they do not share each others DHCP leases. DC1 has some, and DC2 has the others. I've been fortunate not to have a duplicate address leased, but I'd like to get this straightened out before one is.

Is there a compatibility issue between 2008 and 2016 DHCP i overlooked? I'm not able to set a failover in 2016 to anything less than a 2012 DHCP server.
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Cannot delete DHCP scope.  It states the subnet does not exist.  Windows Server 2012 R2

How do I remove it to create a new one?
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In windows there's a way to see DHCP scope statistics. In use, Addresses Available utilization %, etc.  GUI or Netsh CLI.  

Is there a way to do it in linux bind DHCP?

Please advice.
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I have 3 AD servers,all virtual but on two different boxes:
1 and 3 are replicating to each other and now to 2
2 is not replicating to 1 or 3 and also holds DHCP ( I do not want  to  lose this, but I do have DHCP running on 3 also with different zones)H
1 and 3 will replicate to 2 but not the other way around.
1 and 3 are 2008 R2
2 is 2012
I have lingering objects error messages that I can not seem to clean up.

1 is the RID Master
3 is the PDC
2 does not hold a role

Same forest/same domain
All are GCs

Help please!!
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Normally VPN DHCP scope is always setup on DHCP server or device.  At this place I see the scope is completely separate on corporate AD DHCP.
Is there a benefit to have the VPN DHCP scope outside of the DHCP device.

For now I configured it right on OpenVPN server unless i hear otherwise fro myou guys.  Thanks!
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Maybe a bit of a phylosophical question. Is there a benefit to have a miltiple scopes in DHCP?  This place has at least 8-9 scopes.
voip, corp, eng, no-eng, prod,eng-wifi,no-engwifi, guest-wifi, etc, etc,
I never setup that many multiple scopes. Always thought if you do then you doing broadcast thru multiple VLAN and killing the purpose of having a VLAN.

Thoughts?
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I am familiar with making DHCP reservations in Windows Server But am now doing in SonicWALL TZ 215 I can see how this is done, But have some questions when doing this in the ARP section:

What does it mean to Publish Entry?

I assume that I want to bind the MAC address or why would I be setting this up in  the first place?

What is meant by Update IP address dynamically?

In the big picture the user will use PPTP from the Windows server to VPN in.  They have a business app that is Unix based and requires the client system to maintain the same IP address (reservation or static).  So, I need the client to obtain that same IP whether they are in the office or out on the road.

Thank you.
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How can I disable DHCP server running on my iMAC OSX Server.
Windows computers are picking up ip from iMAC as dhcp server and we don't remember installing anything on imac, how can we disable that ?
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One DHCP server has run out of IP addresses to Assign.  Just want to verify this is the correct procedure to expand it.

Deactivate the current scope
Create a new scope with a wider range and use the same exclusions.
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I have an Arris SURFboard cable modem SB8200 and am very happy with it, BUT when I connected my Netgear GS605 5 port switch via a Cat6 cable, the switch will NOT work.  The cable modem is perfectly fine as I can connect it directly to my main computer and get my gigabit speeds.  I called Arris Tech Support and made my way to their upper level tech support.  After our troubleshooting, their conclusion was that I needed a new switch.  

They said I need a routing switch or any layer 3 switch. They mentioned something about it handling DHCP.  There are so many switches out there, can you please recommend a medium to high quality switch at a moderate price.  The goal, of course is for the switch to be able to utilize and deliver the full gigabit speed the cable modem has to the switch and thus throughout my hard wired Cat6 home network.  Thanks.
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Dear experts,

I have a Window 2012 R2 server running DNS, DHCP, and AD DS and a sonicwall firewall. For some reason that my DNS server is not working. When I look at my network connection from Window 7, I can see that IPv4 Default Gateway is 192.168.1.1, IPv4 DHCP server is on 192.168.1.30 but IPv DNS server is on 68.x.x.x It is not pointing to my DNS which should be the same as the DHCP server (192.168.1.30). I am not sure what went wrong as in if there is a mis-configuration in sonicwall firewall/router or the DNS server at 192.168.1.30.

I can see my client PC is not talking to the local DNS server 192.168.1.30 but instead on 68.x.x.x my ISP. Is there a way to configure in order to ensure my client PC will ask my local DNS first if no information can be found then forward to the DNS of my ISP and so forth?  I have set my TCP/IPv4 to Obtain an IP address automatically and Obtain DNS server address automatically. Is there a way to set obtain IP and DNS server automatically rather than set those to static?
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Striggling with dhcp on linux.  
Need to know scope range, reservations, lease hours/days, % scope used, etc.

Here is what I have:   can can you take  apeek and help with commands?

# File managed by Chef

# set this to store vendor strings.
set vendor-string = option vendor-class-identifier;

allow booting;
allow bootp;
allow unknown-clients;
allow client-updates;

authoritative ;
ddns-domainname "corp.companyname.com.";
ddns-update-style interim;
ddns-updates on;
default-lease-time 6400;
filename "pxelinux.0";
max-lease-time 86400;
next-server 10.x.x.x;
one-lease-per-client true;
ping-check true;
update-static-leases true;

option domain-name "corp.companyname.com";
option domain-name-servers 10.x.x.x, 8.8.8.8;
option domain-search "corp.companyname.com", "i.companyname.com", "someothername";
option host-name  = binary-to-ascii (16, 8, "-", substring (hardware, 1, 6));




zone corp.companyname.com {
 primary 10.x.x.x;
 # uses name format could use IP address format
}
# zone 42.10.in-addr.arpa {
#  primary serverhostname;
# }

include "/etc/dhcp/groups.d/list.conf";
include "/etc/dhcp/subnets.d/list.conf";
include "/etc/dhcp/hosts.d/list.conf";
~                                                                                                                                          
~                                                                                                                                          
~     …
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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).