Creating the correct TTN dev_addr for ABP devices

Hi there.

We have some devices that we need to configure as ABP - not ideal but that is the requirement.

The documentation https://www.thethingsnetwork.org/docs/lorawan/addressing/ states that TTN ABP EU devices should use a prefix of 26 01 1 x xx

We are using prefixes here too for different device classes (for example, ABP devices in the eu region start with 0x26011) or to shard devices over different servers

However, when we use the API to generate a ‘formal’ dev_addr https://eu1.cloud.thethings.network/api/v3/ns/dev_addr from the NS

Ref: https://www.thethingsindustries.com/docs/reference/api/network_server/#message:GenerateDevAddrResponse

The prefix is currently returned as 260B xx xx
There does not seem to be a method in the API to specify this is an ABP dev_addr request.

I understand from other forum posts that the prefix is used for network routingt (26/27 prefix) and for internal routing too (xx 01 1 x xx) so it’s probably important to get this right.

So my question is should we generate our own dev_addr with 26011 prefix or is the return from the API call valid? It could be that the documentation is out of date.

Thanks

It’s valid - The Things Network is assigned 26000000/7 so everything from 26000000 to 27FFFFFF is in range.

qf https://www.thethingsnetwork.org/docs/lorawan/prefix-assignments/

@descartes I agree it’s valid at that top level, but the documentation does say that different prefixes within the 26/27 range are used for different device classes (ABP in my case), presumably in internal routing.

We are using prefixes here too for different device classes (for example, ABP devices in the eu region start with 0x26011)

I suppose the safe option would be to use 26011xxx and randomly generate the xxx to comply with both documents.

You might want to consider that you are focusing on an example given in the docs that shows an address prefix. It does NOT state that is the prefix in use. It may have been at the time of writing, but has since changed. What reason would you have to question the return from an API call?

That is one of the least safe options.

The safe option is to ask on Slack.

I’d just try a manual registration on the correct regions console to see what I’m assigned. Because I’d reasonably expect the console to give me an appropriate address - right now I’ve just been given 260BF13A.

If you are registering “some” devices on ABP, you may want to chat with @rish1 about device numbers.

Nope, that is not a safe option. Do not try to outsmart the LNS and just use the values it generates for you.

Thank you - we’ll leave it there then

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