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ER605 DHCP option customization issues

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ER605 DHCP option customization issues

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ER605 DHCP option customization issues
ER605 DHCP option customization issues
2023-01-31 14:41:30 - last edited 2023-01-31 15:42:33
Tags: #DHCP Service
Model: ER605 (TL-R605)  
Hardware Version: V2
Firmware Version: 2.1.1

After upgrading to the newest firmware I was eager to try DHCP option customisation feature.  Unfortunately when added option 43 with custom hex it is not passed to the DHCP clients. Same with option number 222, but for example 249 works like expected. 

 

tcpdump output:

15:37:04.107089 IP (tos 0xc0, ttl 64, id 57267, offset 0, flags [none], proto UDP (17), length 340)
    192.168.0.1.bootps > test.bootpc: [udp sum ok] BOOTP/DHCP, Reply, length 312, xid 0x56a10536, secs 1, Flags [none] (0x0000)
      Your-IP test
      Server-IP 192.168.0.1
      Client-Ethernet-Address xx:xx:xx:xx:xx:xx (oui Unknown)
      Vendor-rfc1048 Extensions
        Magic Cookie 0x63825363
        DHCP-Message Option 53, length 1: ACK
        Server-ID Option 54, length 4: 192.168.0.1
        Lease-Time Option 51, length 4: 7200
        RN Option 58, length 4: 3600
        RB Option 59, length 4: 6300
        Subnet-Mask Option 1, length 4: 255.255.255.0
        BR Option 28, length 4: 192.168.0.255
        Default-Gateway Option 3, length 4: 192.168.0.1
        Domain-Name Option 15, length 3: "lan"
        Hostname Option 12, length 7: "test"
        Classless-Static-Route-Microsoft Option 249, length 4: ERROR: length < 5 bytes
        Domain-Name-Server Option 6, length 4: 192.168.0.1
        END Option 255, length 0
    0x0000:  xxxx xxxx xxxx 9ca2 f4e8 8aa3 0800 45c0
    0x0010:  0154 dfb3 0000 4011 1770 c0a8 0001 c0a8
    0x0020:  0064 0043 0044 0140 d970 0201 0600 56a1
    0x0030:  0536 0001 0000 0000 0000 c0a8 0064 c0a8
    0x0040:  0001 0000 0000 xxxx xxxx xxxx 0000 0000
    0x0050:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0060:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0070:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0080:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0090:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00a0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00b0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00c0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00d0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00e0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x00f0:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0100:  0000 0000 0000 0000 0000 0000 0000 0000
    0x0110:  0000 0000 0000 6382 5363 3501 0536 04c0
    0x0120:  a800 0133 0400 001c 203a 0400 000e 103b
    0x0130:  0400 0018 9c01 04ff ffff 001c 04c0 a800
    0x0140:  ff03 04c0 a800 010f 036c 616e 0c07 7069
    0x0150:  6e67 7769 6ef9 04de adbe ef06 04c0 a800
    0x0160:  01ff

 

UI screenshot:

 

Anyone had success with this? 

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#1
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11 Reply
Re:ER605 DHCP option customization issues
2023-01-31 15:45:18

  @ljarosz 

yes in controller mode, tested with some unifi access points with option 43 in hex, the access point found the right remote controller right away.

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#2
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Re:ER605 DHCP option customization issues
2023-01-31 15:48:39
When this option is configured through controller, not through normal webinterface if I understand you right?
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#3
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Re:ER605 DHCP option customization issues
2023-01-31 15:50:48

  @ljarosz 

yes omdada controller, but it looks like the configurations are similar so it should work in stand alone too I would think

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#4
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Re:ER605 DHCP option customization issues
2023-01-31 15:56:54

  @ljarosz 

 

what do you try to do with option 43? maybe you ned a vendor specific code to get it to work, unifi ned 01:04: in the beginning to work cisco ned f1:04: and so one.

 

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#5
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Re:ER605 DHCP option customization issues
2023-01-31 16:13:54

  @shberge I know that this won't work in my exact scenario, but it is much easier to spot 0xdeadbeef on the interface dump instead of smth more obscure like exact IP address. 

Since you have it working with Omada controller this is definitely some standalone interface issue. I submitted support report to TP-Link. I hope they will look into it. 

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#6
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Re:ER605 DHCP option customization issues
2023-01-31 16:18:35

yes  @ljarosz 

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#7
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Re:ER605 DHCP option customization issues
2023-02-02 06:56:09

  @ljarosz 

Maybe try the Type as IP?

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#8
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Re:ER605 DHCP option customization issues
2023-02-22 12:08:33
I tried and nothing changes. I don't think this has anything to do with the formatting of the UI input, but how it is translated to DHCP service configuration file.
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#9
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Re:ER605 DHCP option customization issues
2023-02-22 14:12:43

  @ljarosz 

 

Agreed, but GIGO applies.  Option 43 is defined as:

 

1 byte :  VendorType

1 byte :  count of payload bytes, typically number of IP addresses x 4

X bytes:  payload, typically IP addresses in hex

 

So your minimum Option43 hex string must be 6 bytes, not 4, and if it is 6, then the second byte MUST be 0x04.

If you want something easy to find use 01:04:de:ad:be:ef

<< Paying it forward, one juicy problem at a time... >>
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#10
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Re:ER605 DHCP option customization issues
2023-02-23 17:36:26

I just realised my mistake. My DHCP client was not requesting option hence that's why according to RFC it was missing in the server response. I wrongly assumed that all of the options provided in settings UI are forced.

 

  @d0ugmac1 You are wrong. I set type to IP and value to 255.255.255.255 and that's what I got in the response:

Obviously I also tested my original value de:ad:be:ef:

So TP-Link nicely encodes it. 

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#11
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