Questions tagged [dhcpd]

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Client requesting an old address to DHCP server bypassing DHCP reservation

I have a somewhat weird question in my home network. Although this is not a "problem", I thought that this would be an opportunitty for learning. Subnet: 192.168.43.64 Range: 192.168.43....
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1answer
303 views

isc-dhcp-server: Using option dhcp-client-identifier in host declaration to identify a client

I'm using isc-dhcp-server version 4.3 (isc-dhcpd-4.3.5) as a DHCP server for my local IPv4 LAN and I'm trying to configure it to use the option dhcp-client-identifier (DHCP option 61) in a host ...
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1answer
20 views

dhcpd unexpectedly destributes a useless route for another subnet as a default gateway

Our dhcpd.conf defines two subnets such like, subnet 192.168.0.0 netmask 255.255.255.0 { option routers 192.168.0.1; # internet gateway } subnet 192.168.1.0 netmask 255.255.255.0 { option ...
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1answer
21 views

DHCPd IP dispatch

For my tests, the following was done with 2 virtual machines. The server is under CentOS7 and the client under Windows 10 (MAC : 08:00:27:bd:3d:ab). After every modification on the server side, I ...
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26 views

ISC DHCP server adding leases given by other server to his database file

Here is my situation: I want to create an Internet-filtering device, using a small ARM device running Debian Buster. It must act as a gateway, and for that purpose I set an ISC-DHCP server on it, that ...
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1answer
57 views

Replay DHCPDECLINE to host by edit ethernet address in dhcpd

I known in dhcpd.conf, I can use following config to assigned a fixed ipv4 address to a client. host h1{ hardware ethernet 11:22:33:44:55:66; fixed-address 192.0.2.2; } range 192.0.2....
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49 views

Dhcpd won't start due to selinux

have searched tirelessly and can't find an answer to this thats not confusing. I have a clean install of centos 6.2 32bit on a machine I use as a router. with selinux enabled dhcpd refuses to start ...
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35 views

Force dhclient to always provide a unique IP from the available pool

I'm running RHEL 7.4 and the dhcpd is controlled by DD-WRT off my router. Tried to use: dhclient -r; dhclient -x; rm -f /var/lib/dhclient.leases; ip a; dhclient -v but it either returns the same ...
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493 views

CentOS 7 DHCP server, get IP but cannot ping server or client

I'm trying to create a nat, however, before I can get that far I need to network two PCs via ethernet. The server looks like this: 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state ...
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1answer
140 views

Exclude subnets from distribution?

In Windows' DHCP server it is possible to exclude an entire subnet from being given out to clients which doesn't have a reservation. They call this "IP addresses excluded from distribution". Now I ...
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1answer
966 views

Edgerouter DNSmasq send updates to BIND

TL;DR: How do I configure the Ubiquiti EdgeRouter, running DNSmasq or DHCPd, and NSupdate, to send its DHCP leases to a central BIND server? I have a system comprised of a few Ubiquiti EdgeRouter X's ...
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276 views

Weird answer of linux DHCP server to gratitious ARP causes DHCP failure

This is a problem, that I ran into recently on a quite heavily configured linux server. This machine runs Samba as an Active Directory Domain Controller, a mail server, a web server, two virtual ...
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1answer
1k views

Multiple IPv6 routers on the same network

I have two ISPs for my home network. They are connected to two separate routers. If I run radvd and dhcpd on both routers at the same time, I get no IPv6 connectivity. My IPv6 connectivity only works ...
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1answer
974 views

DHCP and logging fixed address “leases”

I have been tooling with a dhcpd server that i have been setting up for, well, for the general excitement of it i guess. I have a bunch of different configurations. I have noticed that fixed-address ...
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1answer
734 views

How can I configure DHCP server to issue the same fixed-address by matching with the client identifier in the discover message

I am able to config fixed ip address with hardware ethernet options, but i am trying to assign fixed ip based on client id(option 61) from DISCOVER message. I tried with below configs , but it doesn't ...
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65 views

dhcpd hostgroup in a single file

Is it possible to set dhcpd to read MAC addresses from file, and then to set IP and hostname for those particular hosts? To be more clear - everything is supposed to be in that file: mac, ip and ...
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1answer
2k views

Option 81 in DHCP

Just curious about this. When we enable option 81 on a DHCP network, the DHCP server will start updating the zone that comes along with the client's FQDN. Now, how would client will ever know its ...
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1answer
3k views

how to block incoming DHCP DISCOVERY messages

I'm running ISC DHCP deamon on centOS and want to block unwanted(by clients MAC address) discovery messages before they reach dhcpd. how can I do this with iptables or anything else?
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1answer
65 views

dhcpd daemon taking huge amount of memory and restarting with out of memory error

I have to configure isc-dhcp-server for 1 million clients which listens on 4094 vlan tagged interfaces, where each vlan interface is mapped to a subnet declaration. Therefore in total 4094 subnet ...
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1answer
4k views

Unable to add forward map …: SERVFAIL

DHCPD[4.3.5] error: Unable to add forward map from nvhenz710.hen.mentats.us to 172.24.1.31: SERVFAIL no errs in BIND 9.11.1-P2-RedHat-9.11.1-2.P2.fc26 $ groups named dhcpd named : named dhcpd ...
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2answers
69 views

How To Use host tag In dhcp.conf

My question is simple. I tried to assign a fixed IP address to wlan0 connected users using dhcp.conf. From configuration file: host clientA{ hardware ethernet 00:80:c6:f6:72:00; fixed-address 192....
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1answer
1k views

Isc-Dhcpserver static DHCP missing client-hostname

I got a strange problem with my isc-dhcpserver (Ubuntu 16.04). When clients are requesting from the server, I can see the following output in /var/log/syslog : Jun 21 21:41:25 drake dhcpd[265]: ...
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1answer
2k views

DHCP Client starts sending DHCP Discover messages upon receiving a NAK from another DHCP server

I am trying to set up a DHCP client that is supposed to get its IP address via DHCP. I have configured two DHCP servers (one in 192.168.X.X pool and the other in 162.16.X.X pool). Then, the client ...
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65 views

DHCPS - single mac whitelist, multiple subnets

I am trying to reduce the size of my broadcast domain and, in order to do this, I need to permit hosts from being able to move from one subnet to another at will. We use a mac whitelist for our dhcp ...
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1answer
152 views

dhcpd.conf DNS order is being reset after each cobbler sync

I'm trying to switch the order of DNS servers that my clients machines use by editing the /etc/dhcp/dhcpd.conf file in cobbler. This was the settings before I attempted the change: subnet 10.100.48.0 ...
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2answers
28k views

CentOS 7 DHCP server fails to start (won't enable on specified port)

I have a Cent0S 7 miniPC with a wireless and wired network ports. The wireless port (wlp3s0) is connected as a DHCP client with 192.168.10.X addressing and has DNS resolution. I'm trying to setup the ...
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131 views

dhcp server not starting on CentOS 5 (XenServer 6.5)

I have a host with XenServer 6.5 (based on CentOS 5) that is currently set up using a static IP by following the procedure here. I have been provided with an IP address, netmask and gateway - I ...
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1answer
222 views

DHCP leases file has 200+ instances of the same lease?

I'm not sure what's going on here. I have a CentOS 7 DHCP server, and the leases file is growing at a linear but steady rate - it's re-issuing the same lease to the same MAC over and over again, and ...
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1answer
2k views

“match hardware” in dhcpd.conf not working

I've been trying to get mac addresses with a certain OUI into a certain address pool. I haven't been able to get it to work at all. Here is a snippet of my dhcpd.conf and how it's applied. class "...
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1answer
2k views

How can I clear the DHCP GUI in OSX Server? Ghost clients in the building

I have a few client machines showing up in the network (not only in Server.app but also in various logs), which have "Computer Names" (Bonjour names in Apple-speak) which I don't recognize, but ...
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2answers
5k views

dhcpd not offering reserved static IP returns unknown lease

typically when I reserve an IP for a MAC addr the device when booting up and requesting a dhcp address, will pick up the address I reserved. However recently the request looks like it comes in but ...
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1answer
182 views

fedora dhcpd name server configuration

I'm having a hard time configuring a more modern release of a Fedora DHCP service to replace an older one and the problem is that clients aren't getting the appropriate DNS server information. I had ...
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2answers
7k views

WiFi access point without internet access - iOS devices disconnect

I'm trying to configure a WiFi access point to offer a web service on the local network, without offering clients internet access. The web server has a fixed IP address (let's say 192.168.2.2) and for ...
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1answer
1k views

Client getting wrong option from DHCP server

I'm setting up a machine to load a Debian intallation with PXEBoot, following the guide on the Debian Wiki. I have the boot image sitting on a server, pxe.example.com, at /var/lib/tftpboot/debian-...
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1answer
1k views

dhcpd.conf for PXE/BOOTP boot not working

I'm trying to configure the dhcpd.conf file so that when I boot through the network using PXE / BOOTP, a bare metal server or a virtual machine (KVM) would get an IP address in the 10.0.2.100 to 10.0....
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1answer
802 views

Cobbler/TFTP: No filename or root path specified, but why?

I've installed a new Cobbler server and configured it as a DHCP /TFTP server. I've configured the /etc/dhcp/dhcpd.conf like so: [root@centolel ~]# cat /etc/dhcp/dhcpd.conf ddns-update-style interim; ...
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2answers
1k views

Release dhcp lease after forcing client to disconnect

I configured a wifi access point based on OpenWRT to limit the number of clients to 4 at the same time. For that purpose I gave a limited number (4) IP addresses leaseable by DHCP. After a period of ...
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1answer
191 views

Obtaining the running config for dhcpd

Is it possible to obtain the current running config for dhcpd? I inadvertently wiped dhcpd.conf but have not yet restarted the service. It is currently assigning the correct IPs to my test ...
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2answers
3k views

How to block DHCP traffic using iptables

First let me describe my environment: There is a VM (CentOS) acting as a gateway The gateway VM has to NICs, eth0 connects to public network, eth1 connects to private network eth0 get IP from public ...
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1answer
2k views

DHCP with fixed IP hosts (Ubuntu)

I'm managing an office system that assigns IPs based on the MAC address. The fixed hosts are added in a dhcpd-hosts.conf file which is included in dhcpd.conf. There are some PCs that are not in the ...
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396 views

How can I assign an IP by UID in DHCPd

Here was answered how to assign an IP by MAC address. I want DHCPd server to assign IP by UID. Can i just add record to dhcpd.conf in the same manner? For example: host example { uid 00:...
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1k views

Restrict hostapd wireless client from talking to eachother

How can I keep a wireless client of hostapd from talking to a wired client on the same network or another wireless client on the same network? Here's my network topology: [wired client] --> [...
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1answer
637 views

2 client classes sharing the same subnet range

basically I would like to achieve the followings: using only one subnet different types of user sharing this subnets creating 2 pools accordingly an user class called "l2vpn_user" if matched by MAC ...
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0answers
86 views

DHCPD does not allow filename option with a colon in it

For some reason, tftpboot does not work with a colon in filename parameter: group { filename "node7:linux/pxelinux.0"; host machine_7a { hardware ethernet 02:01:02:02:01:11; fixed-...
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2answers
1k views

OpenBSD ISC-DHCP IPv6 not working?

How to enable dhcp for ipv6 in OpenBSD 5.5. Default dhcpd don't know about IPv6, it says that option -6 is incorrect and do not understand ipv6 config. But it has version 4.X that IPv6 must be enabled ...
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2answers
2k views

ISC dhcpd dynamic bootfile-name. Is this possible?

Actually I want to dinamically assign bootfile-name based on clients MAC. I have tried this config: option bootfile-name concat( binary-to-ascii(16, 8, "", substring (hardware, 1, 6)), ".cfg"); But ...
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1answer
2k views

Cleanup DHCPD leases as well as DDNS Entries

I have a fairly simple set up on a Debian server I'm running. I currently have isc-dhcp-server installed along with bind9. I set up my zone and my reverse lookup zones and set up dynamic updates, it's ...
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1answer
252 views

Assigning option based on class membership inside the subnet section

We are looking for a way to do something along these lines in the dhcpd.conf file: subnet ... { #couple of options for the subnet here pool { allow members of "class-name1"; ...
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4answers
3k views

Fixed dhcp host to automatically expire any lease

I have the following situation: Multiple offices with multiple firewall/dhcp servers. Every time the IT team of some office plugs a new network printer i need to create a fixed-address entry, and ...
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1answer
2k views

ISC DHCP Server scope error

Why am I getting the following error after modifying my dhcpd server config? option space definitions may not be scoped