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Questions tagged [dhcp]

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

The Dynamic Host Configuration Protocol (DHCP) is an auto configuration protocol used on IP networks and an extension of the Bootstrap Protocol. DHCP allows for computers to be configured automatically to communicate with each other over an IP network without the need for manual setup by a network administrator.

The implementation of DHCP relies on a DHCP server to hand out network configuration information to DHCP-capable clients that request an IP address (and other information required or useful in communicating with other devices on an IP network). In addition to an IP address, common configuration information served over DHCP includes a default gateway, subnet mask and DNS sever(s), though there are many more possible configurations that can be sent out using the DHCP protocol.

More in-depth detail on DHCP and its implementation can be found at Wikipedia.

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What is a good DHCP lease timeout configuration

I have generally seen that DHCP lease times are quite long (a day plus) on most defaults. I have a client that seems to have the following problem. They have a DHCP server in a router that is near-saturation (say in a normal work day 80-85% of the…
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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 and go very quickly we need to keep the lease time…
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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 one end of the building, connected to a cheap…
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dnsmasq: mapping 2 MAC addresses to the same IP address

Is it possible to map 2 different MAC addresses to the same IP address? For my backup, I need to connect back from the server to the portable, and I would like to have the same IP both for the wireless and the wired interface. The openwrt web…
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IPv4 To IPv6 Migration Advice

I'm currently working on adding IPv6 capabilities to our network, and I have some questions on what is considered best practice in 2020 to convert some of the IPv4 concepts we are used to into the IPv6 world. In the current setup that I have, we are…
Max Ehrlich
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How to renew dhcp ip address in ubuntu?

This is a simple question in ubuntu server How do I renew a dhcp assigned IP address?
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Reverse DNS records not registered when using DHCP

I've stumbled upon a strange behaviour with Windows machines, which seems to be fairly consistent between all Windows versions from Vista/2008 to 8.1/2012 R2; it doesn't happen instead when using Windows XP or Windows Server 2003. The problem is…
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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 way it is easy to do. According to the…
Niels Basjes
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Why use DHCPv6 over Stateless Address Autoconfiguration?

IPv6 and RFC 2462 provide a means for hosts to configure their own IP addresses via stateless address autoconfiguration. To me this seems like the bee's knees, and it leaves me wondering why someone would want to go through the trouble of…
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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 the primary DNS for any connection, so how would…
Ivan
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DHCP Options for Network Time Server

It looks like there are two options for providing network time settings to a DHCP client; option 004 and option 042. The description for 004 is "Time Server", while 042 specifies NTP. Is there a reason to use one or the other, or is it just vendor…
TimM
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Phones on some switches cannot complete DHCP process

Background I have a Windows DHCP server (Server 2008 R2) handing out addresses for several scopes. One of those scopes is for some Mitel IP Phones. The phones are configured to use dhcp option 125 to get configuration information. When a phone…
Joel Coel
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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 network based on their IP or MAC (These clients do…
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Difference between DHCP options 'Domain-Name' and 'Domain-Search'

What is the difference between the two? I had thought that domain-name would put the client on the specified domain (ie. If the domain-name was set to "foo.bar" the clients FQDN would be 'hostname.foo.bar'), but…
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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 would like a way to create a notification/eventlog…
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