Bug in Archer C6 - DHCP Static vs ARP Static conflict

Bug in Archer C6 - DHCP Static vs ARP Static conflict
Bug in Archer C6 - DHCP Static vs ARP Static conflict
2019-06-10 17:04:26
Model: Archer C6
Hardware Version: V2
Firmware Version: 190115

Hello

 

I found in Archer C6 a probably all new models you implemented a check - you can not set different IP-MAC combination in DHCP Static list and ARP Bind list.

 

Idea is good unfortunatelly this cause a lot of troubles:

 

1. if you need change (switch) for example 2 devices, it is not possible, you can not change DHCP Static because of its ARP Record, you can not change ARP records because you have the device in DHCP Static record.

You need do it like this: delete DHCP Static record, delete ARP Static record, power off devices so they won't be in ARP devices list, then add DHCP static and ARP static records, then you can power on the devices

As you can see, the DHCP <->ARP check is not helpful 

 

2. you also can NOT change Description in DHCP or in ARP list, because you can NOT edit either record, because the record is already in the other list.

 

3. Also all this is not correctly explained, you see only error  "The to-be-added address already exists." and you have no clue that this is about DHCP static <-> ARP static crosscheck, it just looks like it is a bug (This crosscheck was not present in previous TP-Link models).

 

Solution:

A. quickfix: remove DHCP static <-> ARP static crosscheck

B. if you want this check to be present, put DHCP and ARP static list on one page or in one table, or something like this

 

pls be sure this will be reported and fixed in next firmware

 

thx

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5 Replies
Re:Bug in Archer C6 - DHCP Static vs ARP Static conflict
2019-06-11 06:22:00

Hi,

 

I confirmed with engineer, it is not a bug, actually it is normal, the IP & MAC Binding, namely, ARP (Address Resolution Protocol) Binding, is used to bind network device’s IP address to its MAC address. This will prevent ARP Spoofing and other ARP attacks by denying network access to a device with matching IP address in the Binding list, but unrecognized MAC address. And the device can access internet  with this specific IP only.

 

Address reservation is used to reserve an IP address for a specified client device, while the device still can obtain other IP address and access internet. 

 

If you setup a different IP for a device under ARP list and address reservation, there will be conflict, therefore the device cannot work properly; 

 

May it help and have a nice day. 

 

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#2
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Re:Bug in Archer C6 - DHCP Static vs ARP Static conflict
2019-06-11 08:11:07

Yes but this works differently with older models like Archer C2. Please ask engineer how to change Description, if records are set already in DHCP static and ARP static.

or maybe he can read my whole post

 

thanks

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#3
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Re:Re:Bug in Archer C6 - DHCP Static vs ARP Static conflict
2019-06-13 07:58:33

Hi,

 

I did a test at our lab, the description can be changed always, while the DHCP address reservation and the ARP binding won't take effect at the same time; in other word, only one option can be enabled at once, otherwise, you will get the error message mentioned above. 

 

And it is back to the reason I told you before.

 

May it help and have a nice day. 

 

 

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#4
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Re:Bug in Archer C6 - DHCP Static vs ARP Static conflict
2020-10-10 08:46:19

@Kevin_Z 

Well, at my Archer C6 (latest FW 1.3.6 Build 20200902 rel.65591) this DOES NOT WORK.

I have a device in ARP list. I am able to wake it up using magic pocket from WAN side, so the ARP binding is registered and works.

And after wakeup, this device gets DIFFERENT IP address than is on the ARP binding list !!

And of course, separate address reservation is not possible due to ARP/DHCP crosscheck.

 

Standalone reservation without using ARP binding works, but then I am not able to wake up the device.

 

PLEASE fix this

Thanks

Karel

 

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#5
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Re:Bug in Archer C6 - DHCP Static vs ARP Static conflict
2020-10-14 08:23:19

@KarelH 

 

Hello, thanks for bringing this up again.

 

May I know the detailed ARP binding for the device that you need to remotely wake it up? Do you also have it in the Address Reservation list? Are the IP address for it on both lists the same, what is it?

 

Thanks.

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#6
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