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Author Topic: Zyxel VMG3925-B10B and nowtv  (Read 3458 times)

lurch

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Zyxel VMG3925-B10B and nowtv
« on: March 21, 2021, 07:41:09 PM »

Looking at replacing my nowtv hub 2 with a Zyxel VMG3925-B10B and no matter what option 60/61 values I use it fails to connect.

i've extracted option 60
2.90.2471.R|004|NR801|xxxxxxxxxxxx and converted to hex

option 60 I extracted but understand any combination can be used i.e
dsklfjdsklfewui9e7r@nowtv|zzzzzzzz and converted to hex

is there anything i'm doing wrong/missing form these boxes?

https://i.ibb.co/0BJKGqC/Screenshot-2021-03-21-193855.jpg
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burakkucat

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #1 on: March 21, 2021, 10:55:18 PM »

Welcome to the kitz forum.  :)

From your description, it seem (to me) that you have done everything right. However I am not fully up-to-date with the usage of DHCP Option 61, so I really cannot comment any further.

Other members should be able to assist . . . So please wait for subsequent posts.
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meritez

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #2 on: March 22, 2021, 10:13:49 AM »

Welcome to the forums lurch,

@siofjofj made a very detailed post on a gui limitation on the zyxel vmg8x24 regarding option 60 and 61: https://forum.kitz.co.uk/index.php/topic,25176.0.html

Would you be able to confirm the firmware version on your vmg3925-b10b?
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lurch

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #3 on: March 22, 2021, 12:57:54 PM »

Hi thanks for the welcome. It was actually that post that helped me get this far. It's currently running

V5.13(AAVF.12)C0

There is one newer version available on their ftp site should I upgrade?

As an aside i've jsut found VMG1312-B10A running Current Firmware Version: V1.00(AAJZ.1) I could use if this is a better option?

The router will be used for it's parental controls for a non tech savy parent and the 3925 has a more user friendly gui.
« Last Edit: March 22, 2021, 01:24:52 PM by lurch »
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meritez

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #4 on: March 22, 2021, 01:55:00 PM »

I do not think the latest firmware will help, as it's not mentioned in the changelog: ftp://ftp.zyxel.com/VMG3925-B10B/firmware/VMG3925-B10B_5.13(AAVF.13)C0_2.pdf

I'm interested to see if @siofjofj patch would work on the new web interface, or if you will need to downgrade to the older web interface.
Awaiting to see if anyone else will reply
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meritez

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #5 on: March 29, 2021, 06:50:17 PM »

@lurch, did you get anywhere with the vmg1312?

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siofjofj

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #6 on: March 29, 2021, 08:17:29 PM »

Sorry I'm a bit late to this, I must have missed this thread somehow.

i've extracted option 60
2.90.2471.R|004|NR801|xxxxxxxxxxxx and converted to hex
It is not necessary to include option 60 for Sky/NowTV (though doesn't hurt).

option 60 I extracted but understand any combination can be used i.e
dsklfjdsklfewui9e7r@nowtv|zzzzzzzz and converted to hex
I believe the username can't quite be anything, it has to be 12 hexadecimal digits. Something like abcdef123456@nowtv|abcd1234 would suffice.

It's currently running V5.13(AAVF.12)C0 There is one newer version available on their ftp site should I upgrade?
While I do not own a VMG3925-B10B, I note that this version of the manual includes on page 125
LABELDESCRIPTION
Option 61Select this and enter any string that identifies the device.
IAIDEnter the Identity Association Identifier (IAID) of the device, for example, the WAN connection index number.
DUIDEnter the hardware type, a time value and the MAC address of the device.
whereas this older versions suggests on page 65 that only the IAD and DUID can be used (as in your screenshot). Perhaps the newest firmware will allow you to enter the string directly (as in my bold above), rather than as a IAID and DUID? The description in my other thread about setting the IAID to 00000000 is only relevant if using the custom firmware on that page, otherwise the router will insert a bunch of extra stuff that will prevent authentication.

If the newest firmware still doesn't allow entry of an option 61 string, try entering
Code: [Select]
IAID: 00000000
DUID: 616263646566313233343536406e6f7774767c6162636431323334 (this is abcdef123456@nowtv|abcd1234 as hex)
and then capture the result using Wireshark (like you did for extracting the credentials from the NowTV router) and post it here. The mention of "hardware type" in the manual when describing what goes in the DUID gives a hint that the VMG3925 might not have a hardcoded type field, so we might be able to engineer suitable IAID and DUID hex values which will work on the stock firmware (which was impossible for the VMG8924 due to the hardcoded type bytes sent too).

As an aside i've jsut found VMG1312-B10A running Current Firmware Version: V1.00(AAJZ.1) I could use if this is a better option?
The VMG1312-B10A firmware is very similar to that of the VMG8924-B10A and definitely has no versions available which allow direct entry of an option 61 string. They also would not be as good a choice for a combined modem/router/access point as they are only wireless-n capable, not ac like the VMG8924 and VMG3925.

I'm interested to see if @siofjofj patch would work on the new web interface, or if you will need to downgrade to the older web interface.
Something similar to my patch certainly could be made (though I'm sorry to say I don't have time to investigate this at the moment) for the VMG3925 with the new web interface, as the patch itself actually has nothing to do with the web interface whatsoever. It is a modification to the DHCP client itself which results in it ignoring what was entered in the IAID field, not sending any of the 'type' bytes and just passing through the DUID field as-is. Bit of a bodge really.
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meritez

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #7 on: March 30, 2021, 12:38:26 PM »

@siofjofj thank you, I slowly realised that it's a backend patch when reading the patch file.

So if the udhcp package here: https://github.com/trejan/VMG3925-B10B/tree/master/dl was edited it might work?

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siofjofj

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #8 on: March 30, 2021, 06:28:42 PM »

So if the udhcp package here: https://github.com/trejan/VMG3925-B10B/tree/master/dl was edited it might work?
Possibly. My patch applied to the options.c file in the source of the VMG8924-B10A, however a quick look at the same file for the VMG3925-B10B reveals somthing very different that is not doing any of the processing of option 61. A quick grep though the entire udhcp source for the strings 'DUID', 'IAID', '61' and '0x3d' (61 in hex) revealed nothing. My assumption would be that the actual option 61 string is now being created somewhere else (no idea where, it will probably need tracing back from the GUI. Could perhaps try grepping through the entire source for some relevant strings?
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lurch

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #9 on: April 07, 2021, 04:37:11 PM »

Hi @siofjofj

Thanks for the info much appreciated.

I have upgrade to f/w ftp://ftp.zyxel.com/VMG3925-B10B/firmware/VMG3925-B10B_5.13(AAVF.13)C0.zip

When I try and add DUID abcdef123456@nowtv|abcd1234 I get a "No special characters allowed" error it does however accept the hex value like the previous firmware i.e 616263646566313233343536406e6f7774767c6162636431323334

I used IAID: 00000000

I have NOT populated the option 60 box.

I will now need to go to my friends house and try it on their nowtv line to see if it works/capture wireshark. If it doesn't work is there anything else I can try while i'm there to save me making another trip?
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siofjofj

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #10 on: April 07, 2021, 05:13:33 PM »

I have upgrade to f/w ftp://ftp.zyxel.com/VMG3925-B10B/firmware/VMG3925-B10B_5.13(AAVF.13)C0.zip

When I try and add DUID abcdef123456@nowtv|abcd1234 I get a "No special characters allowed" error it does however accept the hex value like the previous firmware i.e 616263646566313233343536406e6f7774767c6162636431323334
What I had more in mind was that there might be an additional box that actually allows direct entry of the string when on the latest firmware. I take it this is not the case then and the manual is a little unclear.

I will now need to go to my friends house and try it on their nowtv line to see if it works/capture wireshark. If it doesn't work is there anything else I can try while i'm there to save me making another trip?
I am next to certain the configuration you currently have will not work. Try capturing the result using Wireshark first (you will need to create a broadband connection of type 'Ethernet' that is otherwise set up with the same parameters as you would use for VDSL, then capture the result using a PC connected to the Zyxel's WAN port). What we need for this to work is for the captured option 61 parameter to be exactly the same hex string you inputted preceded by 3d 1b (3d = 61 in decimal for the option type and 1b = 27 in decimal for the length of the string). If you post exactly what wireshark captures we may be able to come up with something.
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lurch

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #11 on: April 10, 2021, 02:24:10 PM »

Hi I have created a connection on the eth wan port with same details as when I did the xDSL port.

Option 61
DUID: 616263646566313233343536406e6f7774767c6162636431323334 (abcdef123456@nowtv|abcd1234)
IAID: 00000000

Wireshark shows option 61 as
="ÿa0bdcdd639e0@nowtv|aGPcpEmG

https://i.ibb.co/L6DtN7p/Screenshot-2021-04-10-141513.jpg
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siofjofj

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #12 on: April 10, 2021, 02:31:44 PM »

Bad news I'm afraid then. It looks like the VMG3925-B10B does exactly the same thing as the VMG8924-B10A: it inserts 0xff at the beginning of the option 61 string and then 0x00 0x02 between the IAID and DUID. There's nothing you can do about this from the GUI, it will need some form of modified firmware for this to work.
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lurch

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #13 on: April 10, 2021, 02:38:34 PM »

Ahh damn, is this something you would be able to modify the firmware to fix?
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siofjofj

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Re: Zyxel VMG3925-B10B and nowtv
« Reply #14 on: April 10, 2021, 03:29:40 PM »

I'm afraid I'm not well placed to do this as I don't own this device so would be doing it somewhat blind, plus I have less free time than when I produced the patch for the VMG8924. Sorry.

If anyone else on the forum fancies giving it a go, after a bit of digging through the source tree it looks like the file at ./dl/public/zyxel/libzcfg_fe_dal-1.0/zcfg_fe_dal_broadband.c has something to do with it, although it gets modified significantly at build time by the patches in ./package/public-zyxel/libzcfg_fe_dal/patches and I'm having some difficulty piecing it all together.
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