Questions tagged [dhcp-server]

Dynamic Host Configuration Protocol (DHCP)

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Rogue DHCP Server Can't be found

Over the last 3-4 weeks I have been trying to find a rogue DHCP server on my network but have been stumped! It is offering IP Addresses that do not work with my network, so any device that needs a ...
Dave Stuart's user avatar
29 votes
4 answers
59k views

How does a computer obtain an IP address via DHCP?

How does the computer know which device on the network to query? How does the default gateway factor into this? Pretty much, what is the chain of events that occurs when a computer tries to obtain an ...
Bigbio2002's user avatar
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22 votes
2 answers
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What are the possible issues in using very short DHCP lease time (< 1min)?

We have a network setup for a demo, which lasts about 15mn. Our DHCP server is configured to assign ~ 100 addresses (max number of simultaneous connections or our AP) ... but since people might come ...
sebpiq's user avatar
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15 votes
4 answers
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Windows DHCP Server - get notification when a non-AD joined device gets an IP address

SCENARIO To simplify this down to it's easiest example: I have a Windows 2008 R2 standard DC with the DHCP server role. It hands out IPs via various IPv4 scopes, no problem there. WHAT I'D LIKE I ...
TheCleaner's user avatar
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14 votes
10 answers
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Windows 2008 DHCP service fails - "...failed to see a directory server for authorization."

I have a small environment running Windows 2008 R2 where the DHCP service on the domain controller fails every two weeks. The most-visible error is Event ID 1059 and the Event Viewer message is: "...
ewwhite's user avatar
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13 votes
4 answers
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What does a DHCP-client consider to be the "best" answer?

We have training rooms where normally Windows XP is installed (via PXE). The "normal" DNS/DHCP infrastructure are Windows-Servers. The training room has its own VLAN (different from the Windows ...
Nils's user avatar
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11 votes
4 answers
95k views

Force the DHCP server to renew the IP address of a client machine, without doing anything in client machine

I would like to know, if there is a way I could force the DHCP server to renew the IP address of a client machine instantly, without me going to the client machine? In fact, imagine, I don't have ...
SSaikia_JtheRocker's user avatar
10 votes
3 answers
13k views

Why does a DHCP server need a static IP address?

I'm experimenting various network setups using VMs. When I setup the DHCP role on Windows Server, it requires a static IP. I am having trouble understanding why this is necessary from a technical ...
kevin's user avatar
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8 votes
2 answers
28k views

dhcpd multiple domain-name-servers

I know it's possible to assign at least two DNS servers via DHCP. For example: option domain-name-servers 8.8.8.8, 4.2.2.2; But I wanted to know if I could also add a third DNS or if this would even ...
cookM's user avatar
  • 183
7 votes
4 answers
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What happens if the DHCP server comes online after the client devices do?

If I have a Windows PC running a DHCP server. I expect it will take on order of minutes a few to boot. My network will have a variety of other devices from various vendors that will boot within ...
Moby Disk's user avatar
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6 votes
5 answers
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Host DHCP services on server or firewall/router?

I've been debating with myself about the best place for hosting a LAN's DHCP services. I have the option of either on a sonicwall firewall or a Windows 2008 server. The two things I was looking for ...
Force Flow's user avatar
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6 votes
3 answers
56k views

Linux DHCP server option 43 vendor-encapsulated-options, how to format/encode?

I admin the network for a small business which has an IPCop firewall box providing DHCP services to the network (and various other services). The DHCP server in IPCop appears to be dhcpd and IPCop ...
batfastad's user avatar
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6 votes
1 answer
3k views

Can the network still work when DNS & DHCP go offline?

In my LAN I have a Windows server and a Synology NAS for storage, directly attached to the server and provided as storage to the clients through a VM. The server provides the domain controller, the ...
aardbol's user avatar
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6 votes
3 answers
53k views

dhcp server gives "no free leases" error although there should be available IPs

We have a small HPC cluster of about 40 machines running Rocks Linux Distro 6.2 (based on Centos 6.6). I have been trying to add 6 more machines to the system in the last few days. The first 3 were ...
none's user avatar
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6 votes
2 answers
17k views

How to configure a MikroTik hAP ac lite router as a Layer 2 switch?

Here is an overview of the network topology: Both the Fritz!Box 7340 and MikroTik hAP ac lite router currently act as DHCP servers, effectively splitting the network in two LANs. The MikroTik router ...
Serge Stroobandt's user avatar
6 votes
0 answers
6k views

DHCP Server Not Offering to PXE Client

DHCP Server Not Offering to PXE Client BACKGROUND: I'm in the process of adding PXE services to an existing SCCM 2007 server. The SCCM server is separate from the DHCP server (Server 2008 x86) and ...
Colyn1337's user avatar
  • 2,417
5 votes
3 answers
6k views

Stop DHCP client from receiving old IP address on new VLAN

I have one DHCP server running Windows Server 2008 R2. It is configured with one Superscope which contains 5 member scopes. One scope for each one of my subnets. Here is the problem, if I am on VLAN ...
Ruisu's user avatar
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5 votes
4 answers
19k views

Two DHCP server in the same subnet

So I change jobs recently and in this new workplace I've found that we've actually got two DHCP servers. In the very same subnet, and they both have the same scope. I did not set up this but I see ...
Kenny Bones's user avatar
5 votes
1 answer
34k views

DHCP Warning Sign Icon On Windows Server

I have a Windows Server 2008 R2 SP1 Domain Controller. I have the roles AD, DHCP, and DNS installed on this server. I noticed today that there was a warning sign on my IPv4 setting, but not on my IPv6 ...
nate's user avatar
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5 votes
1 answer
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Client not getting address from some DHCP server

I'm working on some embedded devices which should be connected to a large network (hundreds of devices) via ethernet and that should be configured using the DHCP protocol. What I'm experiencing is ...
Luca Carlon's user avatar
5 votes
1 answer
8k views

IPv6 address lifetime: preferred versus valid lease

What is the difference between "Preferred Life Time" and "Valid Life Time" lease. What is the point of preferred and why not just use valid life time lease? Thanks.
user1330287's user avatar
5 votes
1 answer
461 views

Is there a way to classify DHCP requests based on the interface they're coming from?

As the question title states, I want to classify my clients based on the interface their requests are coming from. Can this be done with normal matching? Or should I restrict the DHCP server to only ...
kirbuchi's user avatar
  • 161
5 votes
2 answers
7k views

Why do I get "No subnet declaration" starting ISC DHCP server on subinterfaces?

I have created two subinterfaces on eth0 : eth0:0 with IP 192.168.10.1/24 eth0:1 with IP 192.168.11.1/24 Configured /etc/dhcp/dhcpd.conf like that: option domain-name-server 194.204.159.1; subnet ...
someHOW's user avatar
  • 51
5 votes
2 answers
4k views

Assign fixed IP address via DHCP by DNS lookup

Preface I'm building a virtualization environment with Ubuntu 14.04 and LXC. I don't want to write my own template since the upgrade from 12.04 to 14.04 has shown that backwards compatibility is not ...
Janos Pasztor's user avatar
5 votes
1 answer
2k views

Openwrt isc-dhcpd-4.2.4

Every time the dhcp service starts, it listens not only on 0.0.0.0:67 but also on 0.0.0.0:PORT where PORT is a random number. Anyone knows where this behaviour comes from? root@OpenWrt:/# netstat -...
dash17291's user avatar
  • 151
4 votes
5 answers
3k views

Is there an official way to detect an existing DHCP server?

I'm planning a new feature on our product to support a LAN. Since the installation will be done by relatively non-technical people (it's for boats) I was thinking it would be useful to automatically ...
parsley72's user avatar
  • 224
4 votes
1 answer
320 views

DHCP: Create a scope within a scope

Before I joined the company I am currently working for, they set up a scope to encompass the 10.2.0.0/18 range of IP addresses (10.2.0.0-10.2.63.254). I was recently tasked with adding reservations ...
MotoDave452's user avatar
4 votes
1 answer
11k views

Can a DHCP reservation use an IP address in the exclusion range?

Windows Server 2008 R2, running the DHCP service. DHCP Scope: 192.168.1.1 - 192.168.1.254 Exclusions: 192.168.1.1 - 192.168.1.99 If a reservation uses an IP address in the exclusion range (like 192....
Massimo's user avatar
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4 votes
2 answers
2k views

How can i locate rogue DHCP servers? [duplicate]

I am investigating some odd behaviour on a sub-net, where host registration doesn’t list some of the IPs that some users report having. Now that I’ve seen evince, i want to passively scan for the ...
j0h's user avatar
  • 203
4 votes
2 answers
151 views

Technically, could I use DHCP on a DHCP Server?

I know that it is not usual, but could I use dinamic IP address on a server that is running a DHCP Server instead of setting a static IP address on it? Is there a restriction of my Windows DHCP server?...
Diogo's user avatar
  • 163
4 votes
3 answers
12k views

Multiple PXE server same subnet

I've been struggling with this for some time. I have a few test machines that boot from the network, they receive the boot data from the DHCP server, this tells them who is the boot server where is ...
Termiux's user avatar
  • 161
4 votes
4 answers
10k views

Configuring DHCP on RHEL 6

I have a fresh install of RHEL6 and I am unable to find any config file to do advanced configuration for dhclient. I am trying to find something like dhclient.conf on Ubuntu so I can modify options ...
frisco's user avatar
  • 143
4 votes
6 answers
18k views

How to ignore unused network interfaces in dhcpd on Centos 7

I have a machine running Centos 7 with 8 network interfaces. I have three of those interfaces configured and running. I have configured dhcpd to handle the local lan interfaces. I get the following ...
Michael Gantz's user avatar
4 votes
3 answers
2k views

Ranges for Multiple DHCP Server: Better to overlap or separate? wireless vs ethernet clients?

I know there are mixed feelings about running multiple DHCP servers on one LAN, but I'm wondering about the best way to set their ranges. In my case, I have a router which performs DHCP and also my ...
neildaemond's user avatar
4 votes
4 answers
4k views

Resolving IP address conflicts on a LAN

We have our LAN set up with DHCPD providing fixed IP addresses to the systems. However we are facing IP address conflicts if some one connects a laptop and assigns an IP address belonging to another ...
nitin's user avatar
  • 2,599
4 votes
1 answer
19k views

ISC DHCP Server "Dynamic and static leases present"

i have a problem similar to Fixed and dynamic IPs in ISC DHPD lead to double lease In my DHCP-Log I often receive warnings like Jan 21 10:20:56 dc2 dhcpd: Dynamic and static leases present for 192....
user333163's user avatar
4 votes
1 answer
12k views

Windows DHCP Reservation Outside of Lease Pool

I am very sorry if this has been answered already. I found this post: DHCP Reservation However I wasn't sure if that was related to Windows or Linux DHCP server and I wanted to clearly state my ...
emmdee's user avatar
  • 2,267
4 votes
1 answer
937 views

Running pfSense server after load balancer, dhcp?

I got the following situation: Two wan, load balanced by a hardware load balancing router Wifi network (can be up to twenty AP's) And I need the following: Need a captive portal where clients can ...
Michel's user avatar
  • 183
4 votes
2 answers
3k views

Using DHCP with Multi-Homed NICs

I am trying to steer away from our current manual addressing system and embrace the decades-old wonder of DHCP. In our domain and even at my home network DHCP is great - I can use address reservations ...
tacos_tacos_tacos's user avatar
4 votes
1 answer
10k views

dnsmasq not responding DHCP requests that don't follow a DHCP discover

I have an instance of dnsmasq running on network namespace X, and I run dhclient (or any other dhcp client) from within network namespace Y to obtain an IP address on a given interface. The two ...
Ricky Robinson's user avatar
4 votes
2 answers
3k views

Prefix Delegation and route creation

I'm using the ISC dhcp server version 4.1 for DHCPv6 prefix delegation on a network. When the server allocates a prefix to a client, the server does not create a route for that prefix to the client ...
Jonathan Swinney's user avatar
4 votes
1 answer
31k views

Can not authorize DHCP server

I have run into a strange DHCP problem. The thing is the service is running, but the DHCP is not authorized. However, when I try to do it by right clicking, the option to authorize is not there - I ...
Sandokan's user avatar
  • 514
4 votes
1 answer
5k views

Getting same IP address for cloned Virtual Images

I was trying to install 3 VM and instead of creating them individually (by using the New VM) I actually cloned them. Now after I start the VM (they are running in the bridge mode) all the VM's are ...
bi0s.kidd0's user avatar
4 votes
1 answer
414 views

Why is this checkbox disabled in Windows DHCP server range policy / vendor class management?

I manage several Windows 2012 based DHCP servers and on one of these I came across a peculiarity that I cannot explain and do not know where to correct: In DHCP manager*, expand [server name], then ...
Hagen von Eitzen's user avatar
4 votes
1 answer
4k views

How to disable NetBIOS over TCP/IP on pfSense via DHCP

I have a pfSense applicance running version 2.x. I want to disable NetBios over TCP/IP via the DHCP Server so it is not activated on Windows clients. It's possible to do it with a Windows server but I ...
Florent's user avatar
  • 43
4 votes
1 answer
3k views

Does a Windows host correctly interpret dnsmasq parameters?

I have a network of Windows 10 machines served (DNS and DHCP) by a dnsmasq instance on a Ubuntu server (Ubuntu 15.10, dnsmasq 2.75). The setup basically works (dnsmasq provides addresses and manages ...
WoJ's user avatar
  • 3,657
4 votes
1 answer
689 views

Windows Server 2012 Failover DHCP

I've been tasked with migrating from our current 50/50 scope resilient DHCP servers to new hot standby failover DHCP in Server 2012 R2. Built a test bed with the two DHCP server VMs and created a ...
ATtheincredibleaf's user avatar
4 votes
1 answer
10k views

Windows Server DHCP import/export scopes using netsh.exe

We have Windows Server 2008R2 as domain controller with DHCP Server functionality. Task was to make reserve server on remote site in case of failure of main one. The reserve one will be running ...
user2838376's user avatar
4 votes
1 answer
4k views

DHCP scope for a user class option

In Linux how can I set a DHCP server configuration which will lease IP addresses from scopes which are defined according to user classes. For example the following configuration leases IP addresses ...
Alptugay's user avatar
  • 211
4 votes
1 answer
3k views

DHCPREQUEST and DHCPACK spam in logs

I've recently noticed that my android phone (droid dna, although the thunderbolt that I had before did the same exact thing) is rapidly requesting dhcp info my dhcp server (isc-dhcp-server on debian ...
lacrosse1991's user avatar
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