Dynamic Host Configuration Protocol (DHCP)

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20
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4answers
26k 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 ...
14
votes
2answers
18k views

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 ...
14
votes
4answers
4k views

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 ...
14
votes
12answers
20k views

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: "...
13
votes
4answers
1k views

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 ...
8
votes
3answers
3k 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 ...
7
votes
4answers
40k 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 ...
7
votes
4answers
786 views

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 ...
5
votes
5answers
3k views

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 ...
5
votes
4answers
1k 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 ...
5
votes
1answer
3k views

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 ...
5
votes
1answer
296 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 ...
5
votes
1answer
984 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 -...
4
votes
5answers
1k 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 ...
4
votes
3answers
4k 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 ...
4
votes
1answer
213 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 ...
4
votes
1answer
6k 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....
4
votes
2answers
125 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?...
4
votes
2answers
21k 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 ...
4
votes
4answers
8k 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 ...
4
votes
2answers
306 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 ...
4
votes
3answers
1k 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 ...
4
votes
1answer
605 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 ...
4
votes
2answers
2k 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 ...
4
votes
2answers
673 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 ...
4
votes
1answer
2k 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 ...
4
votes
1answer
77 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 ...
4
votes
1answer
6k 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 ...
4
votes
2answers
482 views

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; ...
4
votes
1answer
5k 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 ...
4
votes
1answer
914 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 ...
4
votes
1answer
1k 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 ...
4
votes
0answers
3k 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 ...
4
votes
3answers
3k views

Cofiguring DHCP server on ubuntu

I am trying to configure DHCP server on Ubuntu but facing some problems. Steps I have followed are given below: Step 1 # apt-get install dhcp3-server I faced following problem during ...
3
votes
4answers
783 views

Can ONE dhcp server serve 2+ network ip range

I have only One dhcp server which has only one interface with ip address 10.0.0.1/24. The dhcpd.conf are like: subnet 10.0.0.0 netmask 255.255.255.0 { <-------working host yyy { ...
3
votes
4answers
538 views

Linux: disallowing access to a network when the user has a static-defined IP address

In my network I run dhcpd3 set up to assign IP addresses only to specific MAC addresses. It works wonderfully, I even integrated it with bind9 to automatically create direct and reverse DNS hostnames ...
3
votes
1answer
15k views

Move DHCP Scopes to existing DHCP Server

We have a remote Domain Controller that is running Server 03'. I'm wanting to retire this box and move to the 03' box that we have locally. I was looking at this guide, but wanted to ensure that it ...
3
votes
2answers
4k views

Unathorizing and removing DHCP role

I am removing DHCP from one of my server (Windows Server 2008 R2 Enterprise), besides running: netsh dhcp delete server server name *server IP* and the removing DCHP role itself from Server ...
3
votes
1answer
594 views

Multiple DHCP relay servers after one another?

Is it possible to have multiple dhcp relay servers in line? IOW DHCP client <=> DHCP Relay A <=> DHCP Relay B <=> DHCP server
3
votes
1answer
308 views

Is there a match on incoming interface in DHCPd classes?

(Note, the title of the question Is there a way to classify DHCP requests based on the interface they're coming from? is what I want answered, but it doesn't actually ask that question for a non-...
3
votes
1answer
88 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 ...
3
votes
1answer
715 views

GPO to Configure DHCP Options

Our environment has approximately 15 Domain Controllers that also provide DHCP functionality to their networks. We have discovered several to have incorrect DNS settings. Their are providing incorrect ...
3
votes
2answers
1k 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 ...
3
votes
3answers
2k views

Secondary DHCP server won't start on Centos 6.2

I'm trying to create a backup DHCP server. Server times are in sync. Primary server starts fine. Secondary server won't start. Error from /var/log/messages is: Sep 15 14:47:45 stream dhcpd: ...
3
votes
2answers
2k views

Setup DHCP split scope but second server won't give leases

My work setup had only one Windows 2003 DHCP Server which resides on DC01. I wanted to improve the redundancy for DHCP so I installed DHCP services on another server (DC02) which is also a DC and DNS ...
3
votes
1answer
110 views

How to generate DHCP Decline scenario / packets

I have a dhcp packets sniffer, which needs to log if it sees dhcp decline response coming from client.I need to know the scenario where client can send dhcp decline response to dhcp server. I tried to ...
3
votes
1answer
418 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 ...
3
votes
1answer
322 views

ISC DHCPD memory leak solutions and or workarounds

Background: I have recently been put in charge of finding the root of and/or fixing a memory leak with an ISC DHCPD (4.2.5-P1) installation on a Debian (Lenny) Unix server. I have been researching ...
3
votes
1answer
7k views

Windows 7 Failing Ping on IPv6 in DHCP Setup

I have set up a test ISC DHCP server that is not connected to an internet with DHCP and DHCPv6. I also have a Cisco 3750G with IPv6 enabled. I have firewalls off on both machines. My Windows 7 ...
3
votes
0answers
65 views

Did I cause this DHCP failure?

I asked this here, it was requested that I move it to this forum instead. I have a question that I need some counsel on concerning DHCP and what may happen in a certain situation. I have a case ...