DHCP server not working when IP reservation is made.

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DHCP server not working when IP reservation is made.

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DHCP server not working when IP reservation is made.
DHCP server not working when IP reservation is made.
2023-01-26 22:35:14
Tags: #DHCP Server not working
Hardware Version: V3
Firmware Version: checked all officially available

Hi everyone,

 

I've got very confusing problem with two TP-Link's. I will describe the problem focusing on the VR400, please note that on the second one, the VR2100, I got identical issue.

 

I was using Archer VR400 for very long time (no problems at all) and last time I started installing IP Cameras. To keep it in proper order, it was necessary to clean up the LAN and setup some IP reservation for all the devices - everything that I have is connected via WiFi. 

Everything is working properly until the Router is reset automatically or by hand. After the reset, the DHCP Server is DEAD, completely. Non device, that is acquiring address from the router can connect - doesn't matter if the device is put or not on the reservation list.

Over the WiFi, the only possibility to get inside the router menu, was setting up fixed IP address of my PC's WiFi adapter (the PC is also on the IP reservation list, manually set IP address is the same like in router).

 

The DHCP Server setup is proper. I got reservations outside the address pool (reservations made on x.x.x.100-150, free address x.x.x.151-199).

And now the magic begins - observations:

1. When the Router is in "zombie DHCP state" I can see on the client list, that devices are attempting to connect and beeing disconnected immediately.

2. When I press "SAVE" on the DHCP setup in Network > LAN menu- VOILA! - every device is beeing connected and gets the proper IP address.

Same behavior when opening for edit any of the entries on the IP address reservation, it's not even necessary to "save" the entry, it just magically starts to work when opened.

3. When the address reservation list is smaller than 8 (7 entries maximum), no problems. The router can reset and works properly when it's up again.

4. I've checked all the official firmware that was available on TP-Link website - nothing helps.

5. It doesn't matter what kind of devices were on the reservation list (was looking for device that could cause the problem?) - the story is the same. 

 

I have send my first VR400 on warranty, got it exchanged for brand new - same problems so I returned it and got refund. I bought instead VR2100 and it behaves the same...

Well, there are 2 options - I'm too stupid to setup ip reservation and the DHCP Server, or the 2 TP-L Router models are good to throw into the garbage and I should get Fritz!, Cisco or Asus instead...

Personally, I think that if this is TP-Link fault that the firmware is bugged for so long time (VR400 is over 2yrs on the market) is unacceptable situation. You get management options that are not working.

 

 

 

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Re:DHCP server not working when IP reservation is made.
2023-02-03 14:25:33 - last edited 2023-02-03 14:28:56

Hi,

 

Little update, maybe this will help someone. I have managed the problem a bit.

At the beginning it's worth mentioning what kind of devices are connected to the Router (please note that now I'm using the VR2100):

Laptops, Smarphones and Tablet, Smar TV, Smart Monitor, Home Cinema, Washer, Dryer, e-book reader, smart plugs, smart led stripe, smart relay, 2nd TP-Link router (MR3420, bridged by WDS do VR2100), TP-Link TAPO Cameras.

 

I've found that:

- smart led stripe, smart plugs, smart relay are making problem when they are on IP reservation (router DHCP is not working),

- WDS bridged secondary router (MR3420) is making same issue as above.

- other listed devices have IP reservation (active) and they are working fine (DHCP server also).

 

When above (problematic) devices are on auto IP receive from router/DHCP server (ip reservation entry for each of them is inactive or just not existing) there is no problem. The router after by-hand reset or automatic reset by the schedule works almost fine.

I say that is almost fine, because I observed, that after the reset, it takes some time for the router to get fully online and DHCP working as intended. I'm not sure if this is correct observation, but there is some kind of correlation with DSL line synchronization and connecting to ISP - as soon as router catches the connection to outside world, some missing devices are getting connected.

 

When I will have more info, I will update this topic. Hopefully it may help someone.

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DHCP Server not working