Re: All About DHCP
Brandi Baylon
DHCP is a client-server protocol in which servers manage a pool of unique IP addresses, as well as information about client configuration parameters. The servers then assign addresses out of those address pools. DHCP-enabled clients send a request to the DHCP server whenever they connect to a network.
The value to which this option is set gives the DHCP server a hint about any required extra information that this client needs in a DHCP response. Some types of set-top boxes set the VCI to inform the DHCP server about the hardware type and functionality of the device. An Aruba campus wireless access point, for example, supplies value 'ArubaAP' as option 60 in its DHCPDISCOVER message.[19] The DHCP server can then augment its DHCPOFFER with an IP address of an Aruba wireless controller in option 43, so the access point knows where to register itself.
In order for rebinding to work, when the client successfully contacts a backup DHCP server, that server must have accurate information about the client's binding. Maintaining accurate binding information between two servers is a complicated problem; if both servers are able to update the same lease database, there must be a mechanism to avoid conflicts between updates on the independent servers. A proposal for implementing fault-tolerant DHCP servers was submitted to the Internet Engineering Task Force, but never formalized.[28][c]
Another extension, Authentication for DHCP Messages[37] (RFC 3118), provides a mechanism for authenticating DHCP messages. As of 2002, this extension had not seen widespread adoption because of the problems of managing keys for large numbers of DHCP clients.[38] A 2007 book about DSL technologies remarked that:
Hello and sorry for bother.
Is there any step by step tutorial for the dhcp server on a openwrt router?
because i see i cant config that on LUCI, and i just want the dchp server because i use pihole and adguard as dns servers.
please let me know or can someone teach me how to do it?
i have like A LOT of lease static ips, my ISP router can handle.
and i just want from 200 to 252 on ip pools
DNS and DHCP configuration /etc/config/dhcp See also: DNS and DHCP examples, dnsmasq, odhcpd OpenWrt uses dnsmasq and odhcpd to serve DNS/DHCP and DHCPv6 by default. Roles Ports Packages Configuration DNS 53/UDP, 53/TCP dnsmasq ...
DNS and DHCP examples See also: DNS and DHCP configuration, DNS encryption, DNS hijacking Introduction This how-to provides most common dnsmasq and odhcpd tuning scenarios adapted for OpenWrt. Instructions Static leases LuCI -> DHCP and DNS...
to be honest i search all the gui of my AP (i have openwrt on a xiaomi router that work as an access point) where i want to put the dhcp server, BUT i couldnt find in the GUI or was too many things i didnt read it
Those will be the general settings for the DHCP Server run on the router. To be honest, I wouldn't really worry about disabling the DHCP Server. Just set your computers up statically, and the enable port forwarding. And you should be good to go.
and you must remember this tips, DHCP Snooping doesn't store Host Information about Every Host on Trusted ports. and when you want to view Hosts Information from DHCP Snooping Database, you cant see any data entry from ports that are Trusted already.
I have questions about the dhcp and the dynamic DNS:
I have installed dns and dhcp on my Tumbleweed system and configured with those with YaST:
I defined a domain pce23.net and an address range from 192.168.1.160 to 192.168.1.199 for more details see the dhcp cong and named.conf below
Dhcp server is working and gives an IP address, DNS server, router to the different PC who connect.
DNS seems half working:
If I connect a windows laptop which is configured to another domain (company.com) I see the next messages in journalctl
I have the feeling that something is wrong in named.conf but I checked it many times and did not found an error.
the laptop with domain is correctly inserted so this means that the dynamic update works but there is no TXT record (?).
The other PC/laptop are not member of a domain because I have no domain controller on my home lan.
So I think that my problem is related to this but I never found something related in all the stuff that I read about dynamic dns update.
No change, I added rules to ufw then "ufw enable" "ufw reload" and still the same in wireschark.
I tried to get the configuration for: smartphone, Ubuntu 16.04 and Windows, the same thing every time: "Getting IP address ..." for several seconds and that's it. There are still no dhcp entries in pihole.log
Maybe I should reinstall the Raspberry pi OS? Maybe I should install Desktop instead of Lite, or Ubuntu 20.04?
is there a way to see devices that don't currently have leases, but have previously negotiated DHCP ?
This would be useful for new devices, VMs, or devices that connect only rarely. For example, my AO Smith water softener goes online when it boots up, and then immediately goes offline. I would like all the MAC addresses from devices that requested DHCP in the past to show up somewhere, with the ability to "forget" (delete) some. This could in theory be obtained from the output of command "dhcp-lease-list -all". It would admittedly take a while to eliminate all the duplicate/renewed leases. This doesn't need to be run/parsed often, though. The main purpose is not to miss new devices, or anything foreign that might suspicious.
Be aware that DHCP servers such as Windows 2003 do not support option 82 and this will cause problems with snooping. We do not use it for this reason, though I have heard folks talk about disabling the snoop information option to get around it. I am not sure if that will actually work though.
If I purchase a router like Netgear or something where I can obviously set a range of IP addresses and let it do dhcp and easily find the devices on the network, can you disable dhcp on the ht2000w. ??? It seems like I would have to. or if I can't, can I just adjust the range to a large 100+ number and then still find the IPs manually on a better external router?
1: Reliability.
Having each server machine rely on dhcp in order to have its networking stack come up correctly adds another potential fault. In a server environment, where you're trying as hard as possible to achieve maximum availability, adding another moving part is not a good idea
If clients receive address allocations from a DHCP server, it is important to be able to predict how they will be affected by any DHCP server downtime. In general, the longer the lease period, the lesser the effects will be if the DHCP downtime remains short. For example, if client lease periods are set to the default of 8 days, clients do not attempt to renew the lease until 50 percent of this period (4 days) has lapsed. If the original DHCP server is unavailable at this time, the client continues with this leased address until 87.5 percent of the lease period (7 days) and then attempts to renew with any DHCP server. With clients attempting to renew after 4 days, even if the DHCP server were to remain unavailable for 2 days, clients would not reach the 87.5 percent rebinding state. Therefore, you do not normally need to worry about any outage that is within 25 percent of the lease duration. Similarly, the shorter the lease times, the shorter the time available to recover the DHCP server.
I read about DHCP message format and I didn't find a mask or broadcast fileds. However, when using dhcpclient command line, I can see using ifconfig that the interface has a mask and broadcast addresses, as below:
You can read more about DHCP here or elsewhere if you google. As you can see, the subnet mask can be acquired from the DHCP server, as well as the broadcast address. This is done through DHCP options when comunicating with the DHCP server.
Wide Area Network (WAN) settings let you control how Google Nest Wifi and Google Wifi connect to the internet. The type of WAN connection you have is usually determined by your Internet Service Provider (ISP). Check with your ISP if you have questions about which settings to use.
This is different from your personal device having a static IP address. Your router can have a static IP address that appears to the rest of the internet. But individual devices connected to your router such as a laptop, smartphone, or tablet can also be given static IP addresses that are used for your local network. These specific static IP addresses won't show up in the outside world. Learn about static IPs for your network devices.
Make sure you know the reasons behind the jetpack.exe tool and the syntax required to carry it out. This can be a useful tool if your databases have expanded beyond 30mb, which might seem ridiculously small database size to worry about; but this is when you are likely to start seeing errors occurring.
I could go on about the use the netsh command, as you can configure an entire DHCP server using it. However, in terms of your Microsoft exam preparation, just be aware of some of the core switches DHCP uses and how they can aid troubleshooting.
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