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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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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isc-dhcp-server handing out IPs from wrong pool

Getting a weird issue where isc-dhcp-server (isc-dhcpd-4.3.3 - ubuntu 16.04) hands out the IPs from the wrong pool to clients. My config is a little strange in that i need to define a lot of /31 ...
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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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ISC-DHCPd how to assign different DHCP settings even if request originated from different subnet?

Network setup 10.0.1.0/28 (VLAN 1) 10.0.1.32/28 (VLAN 1) ISC-DHCPd setup subnet 10.0.1.0 netmask 255.255.255.240 { option routers 10.0.1.1; } subnet 10.0.1.32 netmask 255.255.255.240 { option ...
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How does classification work ISC DHCP Server

man dhcpd.conf does not say anything, how do classes work, when one client matches more than one class. Are all of matched classes used or one just one of them with best match? If all classes are ...
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Why does a manually deleted dhcpd lease return?

DHCPD: 4.3.6 OS: CentOS 8 I removed an entry from the dhcpd.leases file by using Webmin. It seemed to work for a time, but then the entry popped back into the file. Thinking it was a Webmin issue I ...
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Why can't I use IPv6 address for DHCPv4 client option 6 (DNS server)

I am trying to configure options for a DHCP network and the proprietary software (that is layered on top of ISC's DHCP server) that I am using won't allow me to put in an IPv6 address. In other ...
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Prevent dhclient from resetting eth0 when bound with a link-local address via avahi-autoipd?

I have a Windows PC directly connected to an embedded Linux device via Ethernet. On the Linux device, I've installed avahi-autoipd, so that I can establish a connection from the Windows PC to the ...
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One DHCP server assigns IP, but another assigns other options

Is it possible to make isc-dhcp-server send dhcp options like filename, vendor-class-identifier but NOT an IP address for the client? That is, I need dhcpd to send a few options but NOT the client's ...
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84 views

Why is my DHCP client w/ reserved address missing the default gateway?

I'm running isc-dhcp-server on Ubuntu 18.04. Clients without a DHCP reservation are able to get an IP address, subnet mask, default gateway and DNS servers from the pool no problem. As soon as I ...
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406 views

isc-dhcp-server fails if interface not connected on reboot

On Ubuntu 18.04 on my gateway server, I've installed and configured isc-dhcp-server, but it doesn't start up (i.e. it fails to start) if there's nothing connected to enp2s0 after a reboot. Note it ...
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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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55 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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Configuring isc-dhcpd server for DHCPv6 with multiple NTP addresses

I'm trying to configure a DHCPv6 server to provide more than one NTP address (option 56) using the isc-dhcpd server. Is there a currently supported way of doing this? My first attempt was defining a ...
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Clear routes from DHCP option 121

I have 3 subnets 192.168.10.0/24 192.168.103.0/24 192.168.2.0/24 Most of them can route to each other via static routes defined in their respective default gateways. However due to some ...
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How to add more than 32 routes to isc-dhcp-server and separate them to 2 fields?

Is there any way to add long list routes to server? Actually now I can add only 32 routes because we have only 1 octet for them. After adding more than 32 routes I received "Malformed packet" by ...
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126 views

Isc Dhcp-allow only 1 lease from opt82 tag

I'm implementing an isc dhcp server that will be utilizing option 82 tags from our switches to hand out dhcp information/addresses I'd like to deny multiple requests with the same tag (if someone ...
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ISC-DHCPD & BIND9: Adjust hostname for BIND ddns registration

I am running isc-dhcpd-4.4.1 and BIND 9.11.6 daemons on FreeBSD 11.2 server for a small company. dhcpd serves a number of Windows stations (assigning them mostly static IP addresses), several special-...
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ISC-DHCPD & BIND9: Dynamic DNS interaction

I am running isc-dhcpd-4.4.1 and BIND 9.11.6 daemons on FreeBSD 11.2 server for a small company. dhcpd serves a number of Windows stations (assigning them mostly static IP addresses), several special-...
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Proxmox KVM IPv6 Routed not working

I got a /48 v6 assigned by my Provider with a dedicated server, on which I did install Proxmox 5. My Issue is, that the dhcpdv6 should assign the VM a fixed ip, but it does not get the IP assigned. I ...
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200 views

isc-dhcp host using files

I configured ise-dhcp-server, which works fine, but my dhcpd.conf is starting to become very big. I'm trying to find information (without results), on whether it's possible to use something like ...
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How do I purge dhcpd.leases? [duplicate]

I'm running DHCPD (isc-dhcp-4.2.4) on an Ubuntu 14.04 system. The var/lib/dhcp/dhcpd.leases file is getting pretty huge (350MB). Looking in it, there's historical data going back many months about ...
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DHCP client doesn't get address

I'm trying to use a Phytron MCC-1 motor controller which gets its IP only via DHCP (no manual setting). I setup isc-dhcp-server on ubuntu as such: # /etc/dhcp/dhcpd.conf option domain-name "example....
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770 views

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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138 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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113 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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424 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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700 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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140 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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344 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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2k 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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363 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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3answers
5k views

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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662 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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747 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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1answer
843 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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300 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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20k views

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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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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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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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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4k 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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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
231 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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2k 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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540 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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