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Questions tagged [isc-dhcp]

ISC DHCP is open source software that implements the Dynamic Host Configuration Protocols for connection to a local network. It is a reference implementation of those protocols, but it is also production-grade software, suitable for use in high-volume and high-reliability applications. DHCP is available for free download under the terms of the ISC License, a BSD style license.

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Failover Gateway, 2 Server

I have set up 2 DHCP servers that route trough the firewall to the WAN. Both of them act as Gateway. The DHCP has a failover configuration allowing to supply the same network. Now if one of them goes ...
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dhcp server not responding to clients who are making connections the second time and onwards

I have setup a DHCP server on my Ubuntu 14 laptop. eth0 is the port I am using for DHCP server and listed with same name in ifconfig. I followed the exact following steps : Step 1 : sudo apt-get ...
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How to use omshell with ICS DHCP?

In /etc/dhcp/dhcpd.conf have added omapi-port 7911; omapi-key testkey; key testkey { algorithm hmac-sha256; secret QUt1z1O3fxqgSDKILAMXFA==; } but it won't let me connect when I do # systemctl ...
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37 views

windows machine gets assigned wrong netmask

I have a Debian based DHCP server. It assigns correct netmask 225.225.225.0 for all devices (WiFi router, voip, scanner) except for the windows machines. They all get assigned 224.0.0.0 for some ...
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48 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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70 views

DHCP: Advertise DNS Server with port (not 53)

In my network I have a small docker swarm running several apps. Latest I tried to setup two new services offering DHCP with ispcpd and DNS with unbound to the network. Master of the swarm is a new ...
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51 views

ISC-DHCP-SERVER adding incorrect reverse zone entry

I have ISC-DCHP-Server and BIND9 running on Debian Stretch. I am trying to setup Dynamic DNS for my client computers, but I'm struggling with the reverse zone. Currently, when computers request an ...
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37 views

Multi router network and IPv6 DHCP/RA issues - How to assign default routers?

I've again got problems with our LAN. There are 4 WAN gateways all on the same subnet, all with 100M uplink. On IPv4 I advertise default routers using a ISC DHCP Server. On IPv6 there doesn't seem to ...
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128 views

Why would ISC dhcpd ignore vendor options?

I'm trying to use an existing dhcpd to autoconfigure Raritan networked PDUs. This works roughly like PXE booting: there are additional DHCP options that direct the device to fetch a config file via ...
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366 views

ISC DHCP assign pool/subnet to certain MAC addresses

Hej, desperate here! I'm running isc-dhcp-server 4.1 here (with webmin but that's another topic) and want to give some options (tftp-server and bootfile) to network-components that I can identify by ...
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107 views

Disabled dhcp-server on router prevents clients from getting an address

I have a weird issue on my local network which prevents some clients, sometimes acquiring an ip address from the real dhcp-server (x.x.x.3). The dhcp-server is a CentOS VM running isc-dhcp-server for ...
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BIND: DNS failover and high availability with dynamic updates

I am trying to design a system with 2 servers that act as both DHCP and DNS servers with dynamic updates. I am using ISC DHCP and BIND9. It looks like this. Server1 - DHCP primary and DNS master. IP ...
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serving multiple networks with one single DHCPv6 server

I have an ISC DHCPv6 server running on a debian (Stretch) machine and 3 physical networks : net1, net2 & net3 . The router is a Debian machine running the Zebra routing software (See picture below)...
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isc-dhcp-server doesn't start automatically

Running on Astra Linux 1.3, my dhcp service (isc-dhcp-server) is well-configured now and work as expected with a slight nuance - it works only when it's started, but a system don't run it at startup. ...
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120 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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325 views

PXE boot from an other Network

so i got an problem. I set up an Router with Debian9, its task is that Clients in the Network are able to boot from an PXE Server( the PXE Server is on an other Network) I heard sth. about IP-Helper ...
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306 views

fixed-address is not behaving properly with DHCP version 4.2.5

If I configure an IP address range in dhcp, and allocate two addresses to two different MACs using fixed-address, and if those two or one of the systems is not active in the network, then the ...
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68 views

dhcpd rewrite invalid client hostname for ddns

Im using isc-dhcpd and bind9 to do ddns. It is mostly working, but updates from clients with invalid names, like "leif_opo5" or "Danfoss Connect CC" are rejected. I changed the hostname for my phone ...
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Can't start isc-dhcp-server because of the Error : Not configured to listen on any interfaces

I try to set up a wifi access point with hostapd and isc-dhcpd but the dhcp server dont work.The conf file is the same i found in this tutorial: [Hostapd : The Linux Way to create Virtual Wifi Access ...
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710 views

Windows 7 Client flooding network with DHCP requests. Not setting IP

I have a small network, with 15 workstations, SAMBA AD, and a bunch of Virtualized linux servers. All the workstations, and servers are on the same subnet. All workstations are running Windows 7 Pro ...
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DHCP DDNS + Samba AD?

I'm working on moving a small business network away from a Windows Small Business Server. I've set up the active directory using Samba, and it all works well, but I see one potential problem: ...
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692 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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ISC DHCP (Infoblox) takes 30+ seconds to respond to DISCOVERS

Client's DISCOVER packets reach the Infoblox DHCP server through DHCP relays, but Infoblox doesn't seem to be responding. I checked the pcap taken from the DHCP server, I can see there is 3 DISCOVERS ...
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1k views

How can I assign static IP address with a specific gateway in an ISC DHCP Server?

I have a router whose WAN Gateway I want to modify, without other routers in the network being affected. I want to test how the network behaves if I change the gateway for only one router. How could ...
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1answer
1k views

Can I request a specific IP address via DHCP without rejecting an offer of a different address from the DHCP server?

Using isc-dhcp-client on ubuntu server 16.04, there's an option that sounds like it should do what i want: send dhcp-requested-address 10.23.33.254; When this option is present in my dhclient.conf ...
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1answer
131 views

VyOS equivalent of “deny unknown-clients” from dhcpd

I'm attempting to use VyOS as a router and move my dhcp server functionality into it. In my current setup, I have a subnet that only allowed statically mapped clients. I can easily get the static maps ...
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1k 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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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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232 views

Is it possible to declare two ethernet interfaces for the same host in dhcpd.conf?

Ubuntu Server 16.04 with isc-dhcp-server. Within the /etc/dhcp/dhcpd.conf configuration I have stated a reserved address for a host provisioned with dhcp this way: host laptop { hardware ...
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Tell connected devices that this network does not offer internet access

I installed the isc-dhcp-server (version 4.3.3) onto my Raspberry Pi and set it up to assign IP Addresses to devices that are connected to the Ethernet port (via a Switch but that should be unrelated)....
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236 views

isc-dhcp send packet not permitted when using iptables snat

I'm having this issue with iptables snat and isc dhcp. This is the case: I have configured 2 IPs in my network card. Primary and secondary OS: Ubuntu 16.04 2: ens32: <BROADCAST,MULTICAST,UP,...
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dhcpd.conf “Configuration file errors encountered”

I want to set up the isc-dhcp-server, but the dhcp.conf file generates an error while testing with dhcpd -t: ... /etc/dhcp/dhcpd.conf line 6: expecting a parameter or declaration authoritative; ...
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ISC DHCP Server - logging the host name from incoming DHCPDISCOVER requests

in my setup ISC DHCPD 4.3.1 hands out ip addresses only to list of pre-defined hosts, whose mac <> ip association is explicitly entered in the config file. once in a while there'll be DHCP request ...
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1answer
734 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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1answer
555 views

isc dhcp class with more match

Is there any way to define more matches with OR? I would like to create a class with a mac address check, like class "fixVms" { match if substring (hardware, 1, 4) = 00:15:5d:aa; } but I would like ...
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425 views

How do I setup a secondary default gateway using classless-routes in isc dhcp?

Here is a snippet of my dhcpd.conf file subnet 10.3.0.0 netmask 255.255.0.0 { option classless-routes 16, 10,2, 10,3,0,110,16,10,4,10,3,0,110,0,10,3,0,110; } It generates the following routes ...
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1answer
116 views

ISC-DHCP server doesn't share hostnames with failover peer

I'm running 2 boxes with isc-dhcp-server 4.2.4-7ubuntu12.8, and when one of them hands out a lease, it looks like this: lease 192.168.56.228 { starts 3 2017/03/29 02:17:31; ends 4 2018/03/29 02:...
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230 views

TFTP Server for multiple vlans

I have a linux dhcp/tftp server with multiple vlans serving a CMTS. The gist of it is in the CMTS, I tell the cable modems on what vlan I want them to get their address and configuration file from. ...
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102 views

Passing Internet from router to external DHCP server

Please forgive my noobiness but I need some help understanding some things with this set up I'm trying to accomplish and I'm still new to all this. I have a Cisco router, Cisco Catalyst switch, and a ...
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1answer
296 views

Block DHCP clients based on strings in hostname

Using isc-dhcp-server on Debian Jessie, I'd like to block DHCP requests based on parts of their hostnames - specifically, if the hostname contains the RegEx string somewhere "iPhone|android-". My ...
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1answer
45 views

suse isc dhcpd dhcrelay no ipaddress

I have the following setup: Client --> eth2(10.4.0.1/16) - router / - eth1(10.3.0.1/16) --> dhcp-server(10.3.0.150) dhcp-relay If the client starts a dhcp-request ...
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1answer
217 views

rfc 6939 support for dhcpv6 relay

isc-dhcp-server now supports rfc6939 as of version 4.3, and I would like to be able use it as it is quite nice to be able to just use the mac address to identify dhcpv6 clients. However, I can't seem ...
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1answer
2k views

Can't bind isc-dhcp-server to interface

OS: Debian Wheezy DHCP Server: isc-dhcp-server 4.2.2 I need dhcpd to listen to the specific interface on a machine with 2 active NICs. I added INTERFACES="eth5" to /etc/default/isc-dhcp-server but ...
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1answer
441 views

Defining a new location for syslinux configuration files when setting up PXELinux

I am working on a mock up of a PXE server for the place I work. I am trying to put the image files and configuration file in places that keep things a little more organized. Even though my dhcpd....
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1answer
124 views

Having issues with DHCP classes

I'm having issues with DHCP classes matching mac addresses. We have a lot of one type of machine and I want to get the IPMI cards in the same pool. I've tried the following; class "IPMI" { match ...
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1answer
202 views

dhcp 'next-server' outside broadcast domain, without using ip helpers(aka dhcp relay)

Can you set a 'next-server' option in dhcp that is outside of the client's broadcast domain? I'm trying to pxe-boot from a server outside my client's network, using isc-dhcpd In my lab I see the next-...
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1answer
2k views

How to tell ISC DHCP correct zone for reverse zone DDNS update?

I've got an ISC DHCP server running (version 4.2.5) which is configured to dynamically update the reverse zone on a DNS service with the hostname it receives via a dhcp DISCOVER package. It all works ...
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2answers
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dhcp server on raw eithernet (no IP on segment)

I have an isc dhcp server that is running on a server with three network segments. The primary network has an IP address. The other two do not. Can I configure the dhcp server to listen on and dole ...
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218 views

Why use DHCP failover rather than just configure multiple ranges?

Specifically regarding ISC dhcpd (but information regarding the principle in general), what are reasons for choosing a fail-over configuration instead of each server having their own range? Assuming ...
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Which options are required to send a PAC file URL via DHCP to Android devices?

I would like the Android devices which connect to WiFi networks to be automatically configured to proxy their HTTP(S) traffic through a web proxy. There is a PAC file available though an URL, which ...