95
votes
Command line program to test DHCP service
Based on this answer, assuming you have installed nmap (sudo apt install nmap):
sudo nmap --script broadcast-dhcp-discover
Add the -e $interface option if you have more than one network interface. (...
- 3,707
21
votes
How do I manually release a DHCP lease on the DHCP server itself?
Apparently there is no such elegant method to accomplish the job.
So, let's do it manually.
Stop dhcp server.
Check your /var/lib/dhcp/dhcpd.leases file and check for the entry. It contains the ...
- 8,941
20
votes
When the internet is down, so is Active Directory?
You should have your Small Business Server (Server Essentials) doing DHCP and DNS. SBS will automatically disable its DHCP service when it detects another DHCP server on the LAN. (You can verify this ...
- 11.4k
19
votes
Assigning a fixed IP address to a machine in a DHCP network
Determine the IP address that is assigned to your server and then go onto the DHCP and set a DHCP reservation for that server.
- 576
18
votes
Domain connection shows as "unauthenticated"
One possible reason for this issue is when the machine account password gets out of sync with the domain controller.
This can happen, for example, if the computer account in Active Directory is ...
- 2,218
18
votes
How does a router get its IP address assigned?
IANA is the organization responsible for global IP assignments. They assign "blocks" of IP addresses to Regional Internet Registries which are geographically based organizations responsible for ...
- 5,367
17
votes
Accepted
IPv4 To IPv6 Migration Advice
This seemed like overkill to me, we already wont come close to filling
the single /64 but this might be my IPv4 mindset confusing me.
Stop counting hosts, that's IPv4 thinking. Subnets come in one ...
- 31k
15
votes
How do I force Linux to reacquire a new IP address from the DHCP server?
Would comment p.campbell, but I have only 1 reputation and therefore cannot, first I review installed interfaces:
ip addr
release IP from selected interface (e.g. eth0, eth1, enp1s0, sit0, wlan0,...)...
15
votes
KVM/libvirt: How to configure static guest IP addresses on the virtualisation host
virsh net-update is a good command for you (you don't need to restart/destroy your network etc)
see:
https://www.redhat.com/archives/libvir-list/2012-September/msg01380.html
- 151
13
votes
How do I find if there is a rogue DHCP server on my Network?
I suggest starting two terminals, one for monitoring and another for sending a request. Terminal1 will show responses from all existing DHCP servers including MAC address. This example was run on ...
- 251
12
votes
How can I set a search domain (and other resolv.conf parameters) in Ubuntu?
Assuming you are using Ubuntu and a connection named "Wired connection"
edit /etc/NetworkManager/system-connections/Wired connection and add the following:
[ipv4]
method=auto
dns-search=a1.domain....
- 312
12
votes
Command line program to test DHCP service
dhcpdump is good for sniffing and displaying DHCP packets on the network.
E.g.
# dhcpdump -i eth0
---------------------------------------------------------------------------
TIME: 2015-11-27 11:...
- 740
12
votes
Is it possible to configure proxy setting through dhcp?
You can configure your DHCP server for Web Proxy Autodiscovery Protocol:
Create a PAC file and host it on a local web server. Then have your DHCP server provide the URL of the PAC file (e.g. http://...
- 235
12
votes
Assigning a fixed IP address to a machine in a DHCP network
DHCP services differ across many possible implementations, and there are no ranges of IP that are traditionally reserved for static addresses; it depends what is configured in your environment. I'll ...
- 123
11
votes
Accepted
Can vSphere PowerCLI cmdlets execute from a PS1 file?
can I put PowerCLI "code" (Cmdlets, etc.) inside a PS1 file, along with other PowerShell code, and execute it like a normal PS1?
Yes. But if you want it to work as expected (as when you use the ...
- 24.3k
11
votes
Accepted
Interpreting DHCP related message from rsyslog
An XMT Solicit is basically a DHCPv6 (IPv6 DHCP) request. If you're not using IPv6 at all disable it because your instance is trying to request an IPv6-IP.
The problem seems to be that your instance ...
- 1,959
10
votes
How does a router get its IP address assigned?
(Here I'm talking about the customer edge router. The one which is on your LAN. In the ISP network, the router is usually/probably configured manually).
If you have a PPP-based connection (PPPoE, ...
- 1,643
10
votes
Accepted
What are the practical risks of enabling the unsecure DNS updates on Windows?
You should basically never, ever allow non-secure updates. Personally I don't even like that the DNS server even allows you to turn off secure updates. This allows anyone on your network (like a ...
- 55.3k
10
votes
Accepted
DHCP: Create a scope within a scope
Ip addresses are meaningless without a subnet mask. When you say the scope encompasses the whole 10.2.0.0 range and then say that range is 10.2.0.0-10.2.63.254 you're implying a subnet mask of /18 (...
- 109k
10
votes
Accepted
Why does a DHCP-provided DNS IP address becomes a static one in Windows 10?
While typing this question I got the answer from someone who had the same problem: the Obtain DNS server address automatically setting is "inherited", in the sense that if any interface on the machine ...
- 3,517
10
votes
How to add another address range to DHCP server
Of course it doesn't conflict; it's just being stubborn.
It does conflict with your existing scope. Your proposed new scopes are encompassed by your existing scope. In order to do what you want you ...
- 109k
9
votes
Accepted
Changing OpenVPN DHCP pool
OK finally it is solved with some changes on the config file:
port 1194
proto udp
dev tun
ca /etc/openvpn/ca.crt
cert /etc/openvpn/server.crt
key /etc/openvpn/server.key
dh /etc/openvpn/dh2048.pem
...
- 259
9
votes
Changing OpenVPN DHCP pool
To piggyback on Zoltan Szabo's answer and to fulfill the clarifications requested in the comments, here is my take on an answer.
How to change the DHCP address pool?
First things first, the answer ...
- 191
9
votes
Accepted
How does DNSMasq integrate with my router?
DNSmasq does not need to communicate with your router. The DNSmasq service just took over the service of DNS and DHCP and your router does not have to provide that anymore. Since you have disabled the ...
- 4,205
9
votes
IPv4 To IPv6 Migration Advice
First: get that /48. For security and manageability not putting everything in a single broadcast domain (VLAN) is good practice.
Second: for servers just configure the addresses statically. You can ...
- 7,672
8
votes
How to ignore a set of Mac addresses in dhcpd.conf?
From this thread on the mailing list, another option to block specific hosts is:
class "black-hole" {
match substring (hardware, 1, 6);
# deny booting;
ignore booting;
}
subclass "black-...
- 181
8
votes
How do I force Linux to reacquire a new IP address from the DHCP server?
If the MAC address of the interface isn't changed, the DHCP server may assign it the same address when renewing. Therefore, a simple release and renew with dhclient may not acquire a new address. ...
7
votes
libvirt: Change dhcp-setup without restarting
The added net-update command in virsh should allow an dhcp-host update without restarting the virtual network (I have not tested it yet).
man virsh:
net-update network command section xml [--...
- 71
7
votes
Find out the DNS server for a DHCP connection in Linux
One more solution to query the DHCP server:
sudo nmap --script broadcast-dhcp-discover
The output tells you the name server offered by the DHCP server:
Starting Nmap 7.60 ( https://nmap.org ) at ...
- 306
Only top scored, non community-wiki answers of a minimum length are eligible