DHCP stands for Dynamic Host Configuration Protocol and is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol.

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52
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11answers
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How do I find if there is a rogue DHCP server on my Network?

What's the best approach towards determining if I have a rogue DHCP server inside my network? I'm wondering how most admins approach these kinds of problems. I found "DHCP Probe" ...
27
votes
2answers
83k views

Can I have multiple DHCP servers on one network?

This is a Canonical Question about Redundant DHCP Servers. Is it possible to have more than one DHCP server on the same LAN? What are the implications of doing this? What happens if there is ...
26
votes
5answers
4k views

Locate rogue DHCP server [duplicate]

Possible Duplicate: How do I find if there is a rogue DHCP server on my Network? I know this is a serious long shot, but here we go. In the past week or so, for users connected to a ...
22
votes
4answers
1k views

1 Year DHCP Lease

Just a little background I'm a fairly young I.T. Tech working in a school only and only been working in the as a technician for a few years so I would still consider myself a "newbie" Anyway, My boss ...
20
votes
3answers
1k views

How do I protect a low budget network from rogue DHCP servers?

I am helping a friend manage a shared internet connection in an apartment buildling with 80 apartments - 8 stairways with 10 apartments in each. The network is laid out with the internet router at ...
18
votes
4answers
13k 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 ...
16
votes
5answers
6k views

Why does it take seconds to obtain IP address via DHCP?

Out of curiosity, why does it often take seconds to obtain network configuration via DHCP when the CPU is capable of processing millions of operations per second and ping to the router takes a couple ...
15
votes
9answers
59k views

Any way to find unused IP addresses on my network?

How can I locate unused IP addresses on my network? The DHCP server keeps assigning the same address and I need a different IP address to test my application with. The software would need to run on ...
14
votes
4answers
25k views

Ubuntu Server - How Do I Request a new IP From my DHCP Server?

I know there is a simple command for this, but how do I tell my ubuntu server instance to request a new IP address from the DHCP server on eth0?
13
votes
2answers
2k 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 ...
13
votes
4answers
2k 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 ...
12
votes
1answer
2k views

How to set up Google ShortName service for my domain, so that the FQDN isn't needed

The blog post "A 'tinyurl' service for your domain" explains how to set up a ShortName service for your domain using Google Apps. For example, if your domain is example.com and you use Google Apps, ...
11
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 ...
11
votes
1answer
4k views

How to request dhcp (using dhclient) on a virtual interface (i.e. eth0:1)

This seems to work fine: dhclient eth0 ifconfig eth0:1 192.168.1.105 up But not this: ifconfig eth0 192.168.1.105 up dhclient eth0:1 Is there any way to get dhcp on a virtual address?
11
votes
2answers
16k views

Multiple VLANs, multiple subnets, single DHCP server?

At my job we are prepping to transition from multiple LANs connected over slow VPN connections to a single MAN connected over fiber, and I've got a few questions. First of all, we are planning on ...
11
votes
3answers
11k views

Howto setup Cobbler with PXE if you can't change the dhcp server?

In the past I've setup a PXE server several times by making the normal dhcp server return everything needed for network booting: both the regular ip config AND bootinfo in a single dhcp setup. That ...
11
votes
3answers
1k views

Use Windows DHCP/DHCPv6 server without setting a static address

You cannot set the Windows DHCP/DHCPv6 server to listen on dynamic addresses or all addresses, only static addresses. Is there a technical reason for this limitation? Is there any workaround? My ...
10
votes
4answers
35k views

How do I determine what my DHCP server is?

I have a sad network left behind by some careless admins - I am in process of figuring out exactly what services are running where, not excluding the possibility that some services are running from ...
10
votes
2answers
2k views

DNS and DHCP not agreeing on an IP address

I'm having a problem where our Windows Server 2003 domain controller assigns my Windows 7 computer one IP address (x.x.x.75) via DHCP, but reports another (x.x.x.84) via DNS. This causes some ...
10
votes
3answers
788 views

No internet after dhcp lease renews

Today we had a number of machines stop getting internet access. After a lot of troubleshooting, the common thread is that they all had their dhcp lease renewed today (we're on 8 day leases here). ...
10
votes
1answer
5k views

PXE Booting Virtualbox guests in internal networking mode?

I am not sure if this is just specific to my distro's packages or is a vbox limitation. So, any help would be appreciated. Ok, so I have a network of VMs, with one VM acting as a NAT for the other ...
10
votes
2answers
267 views

Windows DHCP server - distribute multiple default gateways?

I'm helping a client through the process of configuring a Windows 2012 DHCP server while migrating from Linux ISC DHCP. In the Windows New Scope Wizard dialog, there is an option to: ...specify ...
9
votes
7answers
13k views

Find out the DNS server for a DHCP connection in Linux

I know they're defined in /etc/resolv.conf, but what if it's not there? And more specifically, how do you find the DNS server returned by DHCP? In GNOME you can use the NetworkManager applet to see ...
9
votes
6answers
15k views

How to make a Macintosh register a Hostname to the DHCP Server?

I have a MacBook running Snow Leopard in our company's internal network, which is basically a Windows domain network. Our TO department complains about my MacBook not specifying a name to the DHCP ...
9
votes
2answers
650 views

MAC addresses on dual-NIC mainboards

Here's a weird problem. We've got a number of devices with dual-NIC mainboards. Some are Realtek NICs, which suck. Some are Intel e1000s, which don't. I've just noticed on 2 machines, one is an ...
8
votes
2answers
821 views

Domain Controller offline for a few days

My primary domain controller died over the weekend, its motherboard is being replaced tomorrow. I have been told that the mac address of the server may change once the new motherboard is installed. ...
8
votes
6answers
6k views

Update hostname from Debian machine with DHCP to a Windows 2008 DNS server

I have a XenServer installation with Debian (lenny) machines created on a daily basis using a script which creates the machine from a template and assigns it with a new hostname. Our network has a ...
8
votes
2answers
6k views

IPv6 DHCP Configuration

I want to set up an IPv6 only network for testing. However, I can't find any HOWTOs or information on setting up DHCP to autoconfigure IPv6 DNS server addresses etc. I use radvd on a ubuntu server to ...
8
votes
3answers
4k views

dhcp-snooping option 82 drops valid dhcp requests on 2610 series Procurve switches

We are slowly starting to implement dhcp-snooping on our HP ProCurve 2610 series switches, all running the R.11.72 firmware. I'm seeing some strange behavior where dhcp-request or dhcp-renew packets ...
7
votes
6answers
1k views

DHCP for data center

Can someone provide cons and pros for having DHCP in a data center? I know this is usually a taboo, but maybe there were developments which alleviate the said issues? Thanks.
7
votes
3answers
6k views

Register A records for my Linux box on my Windows 2008 DNS/DHCP server

I've a network which is mainly Windows: Windows 2008 server (with DNS/DHCP as well as AD), and various mainly Windows machines (servers, XP, 7). I know trying to add few Linux boxes, and can't make ...
7
votes
1answer
4k views

dhclient: What does “RTNETLINK answers: File exists” Mean?

I wanted to update the DHCP lease of an Amazon EC2 instance, so I executed the following command: user@host:~$ sudo dhclient Following that, the system's DHCP lease is updated successfully updated. ...
7
votes
3answers
15k views

How to configure radvd, dhcpd6, routing and /64 subnet based on delegated prefix by DHCPv6-PD server?

My ISP has just started IPv4/IPv6 dual stack service. In order to connect IPv4/IPv6 internet, almost all users usually use a CPE leased by the ISP. But I want to use my Linux router instead of such ...
6
votes
6answers
8k views

Why can Windows machines resolve local names when Linux can't?

I have a small network with Windows and Linux machines connected to a D-Link DIR-825 router. The Windows machines on the network can reach all other machines by name while the Linux machines only can ...
6
votes
5answers
2k views

Is there any way to force my Linux box to always boot up with a self-assigned IP address?

This is perhaps an unusual request: I'm trying to get a Debian Linux box to always give itself a self-assigned IP address (i.e. 169.254.x.y) on boot. In particular, I want it to do that even when ...
6
votes
6answers
10k views

Some DHCP clients end up with wrong DNS server

The scenario: DC running Windows Server 2008 R2 providing DNS + DHCP Cisco 1811 Router as the gateway 30 Windows XP DHCP clients on the LAN The problem: Some workstations are spontaneously ...
6
votes
7answers
2k views

DHCP addressing vs Static addressing for Servers

I'm having a "lively" debate with a work associate about the reasons for or against using DHCP on servers in a network environment. The network environment in particular is a relatively small network, ...
6
votes
7answers
4k views

DHCP server with database backend

I have been looking around for something to replace my (ancient) ISC-DHCPd server. A DHCP server with a database backend sounds like a great idea to me, as I could then have a nice, friendly web ...
6
votes
4answers
2k views

libvirt: Change dhcp-setup without restarting

I'm using libvirt and kvm to virtualize my server. I configured libvirt to start a dhcp-server on the bridge-network-interface to give the vm's their ips. Every VM's gets always the same ip based on ...
6
votes
1answer
148 views

DHCP Server only remembering one lease

I have a Server 2008 R2 DHCP Failover Cluster that serves two VLANs - an office network and a guest WiFi network. Both of the members of the failover cluster are virtual machines (ESXi) and use the ...
6
votes
1answer
3k views

What is DHCP Rebinding?

My external network interface on a gentoo box will produce these errors intermittently (maybe 3-4 a week). It is hooked up to Optimum online, and gets its IP via DHCP. It's always-on, and it almost ...
6
votes
1answer
948 views

Per-client DNS servers with DNSMasq

I am running TomatoUSB with DNSMasq to provide DHCP and DNS services for my local network. What I would like to achieve is to provide alternative DNS servers for one or two specific clients on the ...
6
votes
3answers
767 views

How do I convince Dell blades to PXE Boot

Scenario: Brand new Dell M610 blades. Connected to the network with a 10GE uplink into a Dell PowerConnect M6220 blade switch. DHCP server evidently working, as everything else boots / gets ...
6
votes
3answers
4k views

How do you get dnsmasq to specify alternate DNS servers?

I'm working on a network with ~10 kubuntu desktops (and numerous servers and IP phones) and am trying to get dnsmasq to specify another dns server as a failover. I tried using server=192.168.0.90 ...
6
votes
2answers
1k views

Sending DHCP specific vendor options to a Windows server

My goal is send some information (url and a one-time token) to a windows machine. It's working fine for GNU/Linux servers because I get the information from /var/lib/dhcp/dhcp.lease or similar. This ...
6
votes
1answer
5k views

Why would Windows Server not respond to DHCP DISCOVER?

My network was working just fine and I broke it. There is a Cisco 1711 router which was configured to hand out DHCP leases to the client PCs. I have a domain controller (Server 2008) on the same ...
6
votes
3answers
7k views

OS X equivalent to ipconfig /registerdns?

Network is running a number of Mac's with Snow Leopard and having issues with DNS resolution (running Windows Active Directory environment with Windows DHCP handing out leases). Is there a way to get ...
6
votes
1answer
327 views

Is there a downside to always updating DNS from DHCP?

I've got a Windows 2012 Domain Controller running DNS and DHCP servers. The default setting appears to be Dynamically update DNS A and PTR records only if requested by the DHCP clients. (This is ...
6
votes
1answer
1k views

DHCP in Windows Server 2008R2 don't show leases, from a 2003 i can see them

I inherited a network where the Domain controllers where recently upgraded from 2003 to 2008R2. After the upgrade the DHCP MMC don't show the leases in several of the scopes, only showing a message ...
5
votes
3answers
455 views

DHCP range starts with 194.77.30. Could that lead to problems?

Just noticed that our Lancom router has a DHCP range of 194.77.30.50 - 150. Could that lead to problems? Because sometimes some devices can’t be reached (with static IPS above that range like ...