Menu
What's new
By:
Filters Better Search

DHCP - Double IP's

  • SNBForums Code of Conduct

    SNBForums is a community for everyone, no matter what their level of experience.

    Please be tolerant and patient of others, especially newcomers. We are all here to share and learn!

    The rules are simple: Be patient, be nice, be helpful or be gone!

H

Henrik!

Occasional Visitor
Hi

I often have a problem with devices getting the same IP from the DHCP.
In the network overview I see it says "static" even though it should be DHCP.

Is there a quick fix, when this happens ? Can I restart/clear the DHCP so the devices get new IP's ?
Should I lower the leasetime, which is 86400 ?
I have a couple of reserved IP's, those work fine, and is listed as "manual"

Devices getting the same IP's:
Samsung S8, Samsung Gear S3, 2 different ChromeCasts.

Normally it is fixed by itself after a day, but I want to fix it faster and hopefully eliminate it.

It is not very WAF friendly when the Chromecast is not working because of IP conflict.

Info:
AC68U - firmware 380.68_4
Wifi disabled. Ubiquiti AP Lite for wifi
 
Make sure that if you set a static IP on a device, you use an IP outside of your DHCP range. You should ideally do something like this:

DHCP range: 192.168.1.100 to 192.168.1.199
Static IPs: 192.168.1.200 and higher
DHCP reservation: within the 100 to 199 range

I like keeping the lower range only for infrastructure: router is .1, managed switch is .2, etc... Printers and computers with static IPs are .200 and higher.
 
Also make sure there's no DHCP server running on the Ubiquity.
 
I dont use static ip's. I make dhcp reservations on the asus router.

But often the devices suddenly gets the same ips as if the dhcp server is handing out the same ips. And then the devices is listed as static.

The ubiquiti is just an AP, no dhcp server else where on the net but the asus router.
 
Henrik! said:
But often the devices suddenly gets the same ips as if the dhcp server is handing out the same ips. And then the devices is listed as static.
Click to expand...

That's just not possible, unless you have another device on your LAN that runs a DHCP server, and which conflicts with your router.
 
There is only the asus router as dhcp server.

Is there a log file for the dhcp server I can look at?

Basically I think the devices dont ask for an ip as there leasetime is not expired, so they just take the last one they used. And the problem goes away when the leasetime expires.
 
Is getting same ip address a bad thing?
 
Henrik! said:
Is there a log file for the dhcp server I can look at?
Click to expand...

System Log, as long you don't disable logging of DHCP requests.
 
RMerlin said:
System Log, as long you don't disable logging of DHCP requests.
Click to expand...
My Systemlog is like this (in danish):
Syslog.jpg


I use Skynet and AB-Solution scripts. I think they do some modifications to the log settings ?
So should I change anything here or by going to the terminal ?
 
Check that the network names of the devices don't have a space in the name as this could cause you some grief.
 
Henrik! said:
I use Skynet and AB-Solution scripts. I think they do some modifications to the log settings ?
Click to expand...
AB-Solution directs all Dnsmasq requests to it's logfile when logging is enabled.
Disable logging in AB to send DHCP logs and other Dnsmasq messages to the Syslog.
 
thelonelycoder said:
AB-Solution directs all Dnsmasq requests to it's logfile when logging is enabled.
Disable logging in AB to send DHCP logs and other Dnsmasq messages to the Syslog.
Click to expand...
Thanks alot. I now see this in system log

Code: 
Oct 19 08:04:21 dnsmasq-dhcp[25638]: read /etc/ethers - 9 addresses
So I guess it's displaying the logs now. And I will monitor this and see what is going on.
 
Henrik! said:
Oct 19 08:04:21 dnsmasq-dhcp[25638]: read /etc/ethers - 9 addresses
Click to expand...
This file is read irrespective of AB settings.
If logging is on in AB it just redirects the log output (with the added "log-queries" directive) to the logfile instead of the Syslog.
What AB adds to the /etc/dnsmasq.conf is within the ## begin of AB-Solution entries ## and ## end of AB-Solution entries ## comments in the file.
 
Just to follow up on this, I can now see whats going on

Code: 
Oct 19 16:16:24 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) a4:77:33:90:de:ee 
Oct 19 16:16:24 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:16:24 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:16:24 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:17:31 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:17:31 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:17:36 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:17:36 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:17:36 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:17:36 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:19:21 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) a4:77:33:90:de:ee 
Oct 19 16:19:21 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:19:21 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:19:21 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:20:05 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:20:05 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:20:10 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:20:10 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:20:10 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:20:10 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:21:36 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:21:36 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:26:11 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:26:11 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:28:24 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:28:24 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:28:28 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:28:28 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:28:28 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:28:28 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:31:22 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:31:22 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:31:26 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:31:26 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:31:26 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:31:26 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:34:19 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:34:19 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:34:23 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:34:23 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:34:23 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:34:23 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:36:28 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:36:28 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:36:32 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:36:32 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:37:57 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:37:57 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:42:29 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:42:29 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:44:30 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:44:30 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:44:35 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:44:35 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:44:35 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:44:35 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:45:16 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:45:16 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 16:46:31 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:46:31 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:46:35 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:46:35 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:46:35 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:46:35 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:48:41 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:48:41 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:48:46 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:48:46 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:48:46 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:48:46 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:53:21 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:53:21 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:53:25 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:53:25 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:53:25 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:53:25 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:58:27 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:58:27 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 16:58:31 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 16:58:31 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 16:58:31 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 16:58:31 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 16:59:31 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 a4:77:33:90:de:ee 
Oct 19 16:59:31 dnsmasq-dhcp[25638]: DHCPACK(br0) 192.168.1.242 a4:77:33:90:de:ee Chromecast
Oct 19 17:01:24 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:01:24 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 17:01:29 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 17:01:29 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 17:01:29 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:01:29 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 17:04:12 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:04:12 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 17:04:16 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 17:04:16 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 17:04:16 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:04:16 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID
Oct 19 17:07:10 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:07:10 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee address in use
Oct 19 17:07:14 dnsmasq-dhcp[25638]: DHCPDISCOVER(br0) 54:60:09:da:16:ee 
Oct 19 17:07:14 dnsmasq-dhcp[25638]: DHCPOFFER(br0) 192.168.1.143 54:60:09:da:16:ee 
Oct 19 17:07:14 dnsmasq-dhcp[25638]: DHCPREQUEST(br0) 192.168.1.242 54:60:09:da:16:ee 
Oct 19 17:07:14 dnsmasq-dhcp[25638]: DHCPNAK(br0) 192.168.1.242 54:60:09:da:16:ee wrong server-ID

As I can see I have 2 ChromeCast fighting for the same IP, and one does not acknowledge DHCPNAK commands.
It gets offered a new IP, but it does not take it and keeps requesting the one that's already in use.
The only way to solve this was to power cycle my ChromeCast Audio.
 
Follow the solution the Merlin offered in Post #2 and assign static IPs to the ChromeCasts. I have two Chromecasts on my network both with static IPs and have no problems.
 
Henrik! said:
Yes, when different devices get the same ip, you will have ip conflict.
Click to expand...

Oh, I misunderstand your post. Important devices in my home network( printers, surveillance cameras,
etc.) operate on fixed ip address. I can tell what the device is looking at ip address.
 
You must log in or register to reply here.

Similar threads

K
Solved:RT-AC68P Assigning Static IP's within DHCP Range
Replies
13
Views
676
Kevin G.
K
A
Inconsistencies and broken behavior with client status and DHCP leases - AX86UP 388.6_2
Replies
17
Views
645
ColinTaylor
C
H
How do I change client IP addressing
Replies
3
Views
380
glens
G
ApexRon
Network List and Manual DHCP
Replies
7
Views
607
ApexRon
ApexRon
mekki
Solved UPDATE: No longer required. See thread. - [Feature request] Option for DHCP Query Frequency Backoff Mode
2 3 4
Replies
76
Views
4K
thiggins
thiggins
Similar threads
Thread starter Title Forum Replies Date
Nas.CloudBusinessPortal Double nat & dhcp Asuswrt-Merlin 10
C Need some help with a DHCP problem Asuswrt-Merlin 9
A Inconsistencies and broken behavior with client status and DHCP leases - AX86UP 388.6_2 Asuswrt-Merlin 17
P Solved Router DHCP and DNS not responding to changes Asuswrt-Merlin 35
mekki Solved UPDATE: No longer required. See thread. - [Feature request] Option for DHCP Query Frequency Backoff Mode Asuswrt-Merlin 76
J Need to disable ipv6 dhcp server ip auto assignments in my lan. but leave ipv6 turned on for wan side. Asuswrt-Merlin 8
K Need help with a bad DHCP issue!!!! Asuswrt-Merlin 6
A Ting-fire device can't get DHCP addr direct from Asus router wifi...can get address from Asus router via TP-Link extender Asuswrt-Merlin 14
M AC86U - DHCP not assigning IP. Asuswrt-Merlin 6
E Static route vs manually assigned IP around DHCP list? Asuswrt-Merlin 13

Similar threads

Latest threads

Sign Up For SNBForums Daily Digest

Get an update of what's new every day delivered to your mailbox. Sign up here!

Members online

Total: 896 (members: 26, guests: 870)
Top