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DHCP not working consistently

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DHCP not working consistently

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DHCP not working consistently
DHCP not working consistently
2024-02-21 19:52:57 - last edited 2024-02-22 17:59:47
Tags: #DHCP
Model: OC200  
Hardware Version: V2
Firmware Version: 2.6.1 Build 20220921 Rel.35903

It appears there is a DHCP server running on both the switch and the router. I do not understand how to manage this configuration from the Omada controller to get the correct network behavior.

 

My LAN interface (192.168.10.1/24) is configured with a DHCP range of 100-250, custom DNS servers, and 20 reserved IP address. These do not always work. Some of the machines will come up with an IP address that's not in the pool, not a fixed value, have wrong DNS servers, and using the wrong lease time. Some machines are working as expected.

 

I run a dhcping

sudo dhcping -s 255.255.255.255 -r -v

Got answer from: 192.168.10.3

received from 192.168.10.3, expected from 255.255.255.255

Got answer from: 192.168.10.1

received from 192.168.10.1, expected from 255.255.255.255

no answer

 

Both the switch (192.168.10.3) and the router (192.168.10.1) responded.

Using wireshark I see that both the swtich and the router are responding to DHCP requests. The switch data is wrong and the router data is correct.

 

 

When I look at these packets, the switch response is wrong data. The router response is correct data. Then in the last packet from the router is a message saying wrong server ID.

 

 

 

 

 

Router :  ER605 V2.0   2.2.4

Switch :  SG2210MP v4.20  4.20.1

AP : EAP660 HD(US) v1.0 1.2.10

Controller : OC200 2.0  5.6.4   

Controller Version : 5.6.4

Controller Firmware :  2.6.1 Build 20220921 Rel.35903

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#1
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1 Accepted Solution
Re:DHCP not working consistently-Solution
2024-02-22 17:59:29 - last edited 2024-02-22 17:59:47

  @Clive_A 

 

How did the switch become a DHCP server? No idea. I plugged everything in, then had the Omada Controller Adopt the switch. Later, my problems started.

 

I was able to solve this problem by having the Omada Controller "Forget" the switch. Then I logged into the switch, which now is reset to factory defaults, and set the password. Told the switch the controller's IP address. Then logged into the Controller and "Adopted" the switch again. Now everything is behaving as it should.

 

How I got into this situation is unknown to me. I just unboxed all this TP-Link gear, followed some tutorials on how to connect and get the Controller to adopt the devices. Everything needed a firemware update, so before I did anything else, I ran the firmware updates. Once that was done, I setup my VLAN's, VPN's and configured IP reservations. It was during the last step that I noticed the IP address were wrong on many devices.

 

Thanks Clive for taking the time to respond.

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Re:DHCP not working consistently
2024-02-22 03:01:11

  @Chrisasnyder 

 

Check if there is only one DHCP server in your network, suggest using the router as the DHCP Server.

Just striving to develop myself while helping others.
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Re:DHCP not working consistently
2024-02-22 06:35:52

  @Virgo 

 

I agree and checked exactly that. The router (192.168.10.1) and the switch (192.168.10.3) are both devices manged by the Omada controller. You can see from the packet capture that for some reason the switch is responding to DHCP requests before the router.

 

The simpler question is how do I have the Omada controller tell the switch to stop being a DHCP server?

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#3
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Re:DHCP not working consistently
2024-02-22 07:38:04

Hi @Chrisasnyder

Chrisasnyder wrote

  @Virgo 

 

I agree and checked exactly that. The router (192.168.10.1) and the switch (192.168.10.3) are both devices manged by the Omada controller. You can see from the packet capture that for some reason the switch is responding to DHCP requests before the router.

 

The simpler question is how do I have the Omada controller tell the switch to stop being a DHCP server?

Simpler question, how do you set up the switch as the DHCP server? Then it'll answer your question.

By default, the switch is NOT the DHCP server.

If you don't agree with me, you can simply reset the switch and test it with the default settings.

 

Of course, you will get the wrong IP when two DHCP servers are responding at the same time. Winner takes all. The first response that arrives will be the IP of the device.

 

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Re:DHCP not working consistently-Solution
2024-02-22 17:59:29 - last edited 2024-02-22 17:59:47

  @Clive_A 

 

How did the switch become a DHCP server? No idea. I plugged everything in, then had the Omada Controller Adopt the switch. Later, my problems started.

 

I was able to solve this problem by having the Omada Controller "Forget" the switch. Then I logged into the switch, which now is reset to factory defaults, and set the password. Told the switch the controller's IP address. Then logged into the Controller and "Adopted" the switch again. Now everything is behaving as it should.

 

How I got into this situation is unknown to me. I just unboxed all this TP-Link gear, followed some tutorials on how to connect and get the Controller to adopt the devices. Everything needed a firemware update, so before I did anything else, I ran the firmware updates. Once that was done, I setup my VLAN's, VPN's and configured IP reservations. It was during the last step that I noticed the IP address were wrong on many devices.

 

Thanks Clive for taking the time to respond.

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#5
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