# Gateway ID : x-FFFF-y or x-FFFE-y?

**URL:** <https://www.thethingsnetwork.org/forum/t/gateway-id-x-ffff-y-or-x-fffe-y/16331>\
**Category:** Gateways\
**Created:** [July 28, 2018, 1:41pm UTC](https://www.thethingsnetwork.org/forum/t/gateway-id-x-ffff-y-or-x-fffe-y/16331 "2018-07-28T13:41:52Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![ivo\_noorhoff](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/ivo_noorhoff/32/35697_2.png) [@ivo\_noorhoff](https://www.thethingsnetwork.org/forum/u/ivo_noorhoff)\
**Post date:** [July 28, 2018, 1:41pm UTC](https://www.thethingsnetwork.org/forum/t/gateway-id-x-ffff-y-or-x-fffe-y/16331/1 "2018-07-28T13:41:52Z")

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I’ve had some trouble with my gateway which i solved by changing the gateway ID from x-FFFF-y or x-FFFE-y and removing and adding the gateway.The gateway is visible again.It may have been the raindance or the ID change but I’m looking for some clarification on how TTN expects the the ID to be generated from the MAC ID.

This [post](https://www.thethingsnetwork.org/forum/t/deveui-for-non-hardware-assigned-values/2093/27) mentions “_In other words, the EUI-64 value was generated by inserting either the value FFFEhex or the value FFFFhex in between eui48[2] and eui48[3]._”

Another [post](https://www.thethingsnetwork.org/forum/t/issues-with-new-pi-based-lora-gateway-using-linklabs-shield/13022) mentions “_For the gateway ID you need to use the MAC address from your ethernet interface with FFFE inserted in the middle._”.

Is there a convention within TTN ? Can someone point me to the standard ?

Thanks, Ivo

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**Author:** ![kersing](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/kersing/32/44777_2.png) [@kersing](https://www.thethingsnetwork.org/forum/u/kersing)\
**Post date:** [July 28, 2018, 4:02pm UTC](https://www.thethingsnetwork.org/forum/t/gateway-id-x-ffff-y-or-x-fffe-y/16331/2 "2018-07-28T16:02:20Z")

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> [@ivo\_noorhoff](#):
>
> Is there a convention within TTN ? Can someone point me to the standard ?

This is an global convention, check [this Microchip document](http://www.microchip.com/stellent/groups/SiteComm_sg/documents/DeviceDoc/en542943.pdf) for more information. For more information on the use of both ffff and fffe see [this ietf forum posting](https://www.ietf.org/mail-archive/web/ipv6/current/msg06035.html).

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**Author:** ![arjanvanb](https://www.thethingsnetwork.org/forum/user_avatar/www.thethingsnetwork.org/arjanvanb/32/46626_2.png) [@arjanvanb](https://www.thethingsnetwork.org/forum/u/arjanvanb)\
**Post date:** [August 17, 2018, 10:06am UTC](https://www.thethingsnetwork.org/forum/t/gateway-id-x-ffff-y-or-x-fffe-y/16331/3 "2018-08-17T10:06:59Z")

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> [@ivo\_noorhoff](#):
>
> This [post](https://www.thethingsnetwork.org/forum/t/deveui-for-non-hardware-assigned-values/2093/27) mentions “_In other words, the EUI-64 value was generated by inserting either the value FFFEhex or the value FFFFhex in between eui48[2] and eui48[3]._”

For future reference, that quote is written in the past tense, and that very same post also mentions (emphasis mine):

> [@DevEUI for non-hardware assigned values](https://www.thethingsnetwork.org/forum/t/deveui-for-non-hardware-assigned-values/2093/30):
>
> But beware it also notes:
> 
> > Mapping an EUI-48 assigned with an MA-S/OUI-36 or MA-M assignment to an EUI-64 potentially creates a duplicate of an EUI-64 assigned with a different MA-S/OUI-36 or MA-M. The IEEE RA has taken appropriate actions to mitigate creation of duplicates based on this mapping but, to protect the integrity of EUI-64 identifiers, **this mapping is deprecated**.

(That said, chances for collisions with officially assigned EUIs within the very same TTN network are low.)