Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients

Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients

Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Monday - last edited Tuesday
Model: ER707-M2  
Hardware Version: V1
Firmware Version: 1.2.4 Build 20241031 Rel.78300

I have a flat single LAN network with no other DHCP servers, and even have the LAN VLAN configured with "Legal DHCP Servers" set to the IP of the ER707 IP (192.168.4.1). Starting with in the last week or two, multiple clients (but only a few out of ~100) have started to be given an IP address other than what they are configured for, which is causing problems since they have some IP-specific policies that then break. When this happens, I cannot ping, or see anything else active, on the IP address they are supposed to receive via DHCP from the router, so it is not that the IP is in use. Also, as soon as I reboot the ER707 the problem fixes itself for a while at least and the devices resume being assigned their correct configured Fixed IP. In the even log I see logs like this - note that 4.81 is configured as the Fixed IP for this MAC (and I have even now set it as an IP-MAC binding to see if that would help, it did not):

Gateway DHCP Server Module Information    DHCP Server rejected the request of the client[MAC: 00-9d-6b-f6-87-97 IP: 192.168.4.180]. Mar 30, 2025 09:51:13 pm    

Gateway DHCP Server Module Information    DHCP Server allocated IP address 192.168.4.180 for the client[MAC: 00-9d-6b-f6-87-97]. Mar 30, 2025 09:51:13 pm    

Gateway DHCP Server Module Information    DHCP Server rejected the request of the client[MAC: 00-9d-6b-f6-87-97 IP: 192.168.4.180]. Mar 30, 2025 09:48:52 pm    

Gateway DHCP Server Module Information    DHCP Server allocated IP address 192.168.4.180 for the client[MAC: 00-9d-6b-f6-87-97]. Mar 30, 2025 09:48:52 pm    

Gateway DHCP Server Module Information    DHCP Server allocated IP address 192.168.4.180 for the client[MAC: 00-9d-6b-f6-87-97]. Mar 30, 2025 09:47:41 pm    

Gateway DHCP Server Module Information    DHCP Server rejected the request of the client[MAC: 00-9d-6b-f6-87-97 IP: 192.168.4.81]. Mar 30, 2025 09:47:40 pm

 

I will attach screenshots of the relevant configuration. This only recently started happening, but I am not sure exactly when it first began. I did somewhat recently update the controller to 5.15.20.16, and also updated two of my Omada switches to fix a different bug:

SG2008P v3.20    3.20.5 Build 20250117 SG2008Pv3_en_3.20.9_[20250304-rel77614]_up.bin Mar 23, 2025 11:14:22 pm
SG2210MP v4.20    4.20.6 Build 20250117 SG2210MPv4_en_4.20.10_[20250304-rel77614]_up.bin Mar 23, 2025 11:06:35 pm
 

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#1
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1 Accepted Solution
Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients-Solution
Tuesday - last edited Tuesday

Hi @daubstep 

Thanks for posting in our business forum.

daubstep wrote

  @Clive_A I'll get set up to try and get a packet capture - it will be a little more "fun" with a wifi device....

Just to clarify, this just started happening on multiple devices that have not changed (and the network hasn't changed, other than the mentioned switch and controller software updates) in a long time, and they have all been working correctly up until now - so these aren't newly configured fixed IPs, they've been configured and working for months and this behavior where the DHCP server rejects the request for the configured IP and instead assigns a different IP has recently started.

One sec. Does it happen to the wired?

I recalled that there is a problem with the DHCP reservation on ER707-M2. The issue happens to the 1.2.3 and 1.2.4 and is known. Fix should be included in the next release.

The DHCP reservation has to be effective until a reboot.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update!Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.
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#6
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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday

Hi @daubstep 

Thanks for posting in our business forum.

The system now will report anything related to the DHCP in the log now. If that bothers you, you can disable them in the settings.

About this log, it's a wireless device joining and disconnecting the network several time and it shows this rejection after it has successfully acquired an IP address from the DHCP server.

I assume this is not a problem with either one of them. It seems to be the device switching between the AP's, and it thinks this is a new network and requested the DHCP again.

It should not impact it at all. It should work okay as far as I can see.

 

Just this device's designed to send the DHCP request whenever it joins a network. And the server already assigned the IP to this MAC address(device). So, it rejects the request and tells it no.

 

The controller will add more and more logs for transparency, and that may cause unnecessary concerns, of course, and will display the logs that were there before, but we did not display them in the past controller versions.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update!Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.
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#2
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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday - last edited Tuesday

  @Clive_A Thanks for replying - I think you missed the point of my post. I have clients configured to use fixed IPs, but the DHCP server denies them their configured IP, which is logged (but without a reason) and gives them an IP other than is configured in DHCP. This just recently started. The logs aren't the problem, but they document the problem.

 

In this log example, the client is configured (see all the screenshots) to be assigned IP "192.168.4.81", it requests this IP, the DHCP server rejects this request, and instead assigns it 192.168.4.180, which is not configured for this device (see the screenshots). This is causing active problems due to access controls for this device set up for the assigned "192.168.4.81" IP address which the router's DHCP server just started rejecting, until a router reboot, after which it works correctly for <24hrs.

 

In one of the screenshots, you can see the client list showing the device was assigned 4.175 next to the Fixed IP Configuration showing it should be 4.81.

In the screenshot of the logs for two days, you can see it working correctly for 4.81, being rejected and assigned the wrong IP address, then I reboot the router (not shown in the logs here) and things work for the rest of the night on the 30th and into the morning of the 31st, but by the afternoon of the 31st it is rejecting the DHCP request and assigning the wrong IP again - all to the same MAC address, which is the MAC address configured as shown in the other screenshots. Finally, at 4:26, after another router reboot, you can see the device being correctly assgined the 4.81 IP address again.

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#3
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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday

Hi @daubstep 

Thanks for posting in our business forum.

daubstep wrote

  @Clive_A Thanks for replying - I think you missed the point of my post. I have clients configured to use fixed IPs, but the DHCP server denies them their configured IP, which is logged (but without a reason) and gives them an IP other than is configured in DHCP. This just recently started. The logs aren't the problem, but they document the problem.

 

In this log example, the client is configured (see all the screenshots) to be assigned IP "192.168.4.81", it requests this IP, the DHCP server rejects this request, and instead assigns it 192.168.4.180, which is not configured for this device (see the screenshots). This is causing active problems due to access controls for this device set up for the assigned "192.168.4.81" IP address which the router's DHCP server just started rejecting, until a router reboot, after which it works correctly for <24hrs.

 

In one of the screenshots, you can see the client list showing the device was assigned 4.175 next to the Fixed IP Configuration showing it should be 4.81.

In the screenshot of the logs for two days, you can see it working correctly for 4.81, being rejected and assigned the wrong IP address, then I reboot the router (not shown in the logs here) and things work for the rest of the night on the 30th and into the morning of the 31st, but by the afternoon of the 31st it is rejecting the DHCP request and assigning the wrong IP again - all to the same MAC address, which is the MAC address configured as shown in the other screenshots. Finally, at 4:26, after another router reboot, you can see the device being correctly assgined the 4.81 IP address again.

When you set a new reservation to a device, both the server and the client should be rebooted.

For the server, it should have the previous IP and MAC binding expire. After this expiration, you connect the client. Or you gotta force both of them to reboot.

 

More specifically, I need Wireshark results and see how they interact. If it is the client keeps requesting or renewing the wrong or the router is giving the previously unreleased IP or sending a completely wrong IP at the first DHCP request.

How Does DHCP Work? Common Questions and Solutions 

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update!Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.
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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday

  @Clive_A I'll get set up to try and get a packet capture - it will be a little more "fun" with a wifi device....

Just to clarify, this just started happening on multiple devices that have not changed (and the network hasn't changed, other than the mentioned switch and controller software updates) in a long time, and they have all been working correctly up until now - so these aren't newly configured fixed IPs, they've been configured and working for months and this behavior where the DHCP server rejects the request for the configured IP and instead assigns a different IP has recently started.

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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients-Solution
Tuesday - last edited Tuesday

Hi @daubstep 

Thanks for posting in our business forum.

daubstep wrote

  @Clive_A I'll get set up to try and get a packet capture - it will be a little more "fun" with a wifi device....

Just to clarify, this just started happening on multiple devices that have not changed (and the network hasn't changed, other than the mentioned switch and controller software updates) in a long time, and they have all been working correctly up until now - so these aren't newly configured fixed IPs, they've been configured and working for months and this behavior where the DHCP server rejects the request for the configured IP and instead assigns a different IP has recently started.

One sec. Does it happen to the wired?

I recalled that there is a problem with the DHCP reservation on ER707-M2. The issue happens to the 1.2.3 and 1.2.4 and is known. Fix should be included in the next release.

The DHCP reservation has to be effective until a reboot.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update!Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.
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#6
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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday

  @Clive_A I believe it has happened to at least one wired device. The one I've included in the logs here happens to be wireless and has caused the most problems (likely being mobile it renews its lease more often than wired devices). Do you know what the ETA is on the new version (or a beta) with the fix? I have also seen another user posting with the same random wrong-DHCP issue also with a ER707-M2 over in the /r/TPLink_Omada subreddit.

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Re:Suddenly getting "DHCP Server rejected the request of the client" for multiple Fixed IP clients
Tuesday

Hi @daubstep 

Thanks for posting in our business forum.

daubstep wrote

  @Clive_A I believe it has happened to at least one wired device. The one I've included in the logs here happens to be wireless and has caused the most problems (likely being mobile it renews its lease more often than wired devices). Do you know what the ETA is on the new version (or a beta) with the fix? I have also seen another user posting with the same random wrong-DHCP issue also with a ER707-M2 over in the /r/TPLink_Omada subreddit.

This issue only happens to the ER707-M2. Someone has reported it before.

I learned it is known from the dev. They are aware of it but did not provide the ETA.

Best Regards! If you are new to the forum, please read: Howto - A Guide to Use Forum Effectively. Read Before You Post. Look for a model? Search your model NOW Official and Beta firmware. NEW features! Subscribe for the latest update!Download Beta Here☚ ☛ ★ Configuration Guide ★ ☚ ☛ ★ Knowledge Base ★ ☚ ☛ ★ Troubleshooting ★ ☚ ● Be kind and nice. ● Stay on the topic. ● Post details. ● Search first. ● Please don't take it for granted. ● No email confidentiality should be violated. ● S/N, MAC, and your true public IP should be mosaiced.
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#8
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