i am trying to find out if it is possible to run a Cisco ISR (1000/4000) router directly and without ONT on a GPON port. To my knowledge there is no NIM module for an ISR4000 for this. Does anyone know a method to do this (maybe via a special SFP that emulates the ONT or similar)?

The component should be compatible with definition 1TR112 of Deutsche Telekom.

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    – Ron Maupin
    Nov 19, 2022 at 22:40
  • cisco.com/c/en/us/products/routers/… there the list of sfp modules on the bottom. It states GPON modules as third party supported but only on 4461. Dec 6, 2022 at 22:37

3 Answers 3


Possible? Maybe. There are various ONT-in-a-SFP modules out there. [GPON, XGS-PON, EPON...] I don't know of any "approved" by Cisco, or DT for that matter. And I've not heard of anyone using one in a Cisco. However, I have heard of other devices not being happy with them -- they assume the SFP is a simple optic that is instantly ready, ONT SFP's tend to run OpenWRT (yeap) and take a while to boot, worse yet, some of them don't contain a PROM, so they can't even be identified until the mini-OS boots. [Cisco switches hate that.]

[BTW, there are entire OLT's in an SFP, too. How's that for miniaturization.]


I'm afraid, a "special SFP" for a simple 1000BASE-X port isn't technically possible as GPON uses time-division multiple access (TDMA) and an SFP would require considerable intelligence and buffering capacity.

Any router that you connect directly would need to actively support G.984 (or 1000BASE‑PX10/20‑D, depending on your ISP) which isn't all too likely. [...] I'm not too much into Cisco gear, but they list a "3rd Party GPON SFP. Reach out to local account team" for the 4461 - so it is possible but support is rather scarce. Check https://www.cisco.com/c/en/us/products/routers/4000-series-integrated-services-routers-isr/relevant-interfaces-and-modules.html

1TR112 aka UR-2 is DSL based, so I don't think that's the right spec...

You might also want to check your SLAs for where exactly the handover port is located. If it's the ONT port, connecting your own gear to the fiber breaks contract.

  • 1
    There is an Amendment (14) of 1TR112 which expands the xDSL Definition to GPON telekom.de/hilfe/downloads/1tr112.zip Jul 8, 2022 at 15:03
  • @AndreasSchaefer Well, live and learn - thx! That's all G.984 but given the strict requirements you should clear them first with Cisco if your ISR is capable of interfacing that.
    – Zac67
    Jul 8, 2022 at 16:32

just to provide some answers:

we tested a lot in the last weeks/months. There are several products on the market that work quite well in my environment.

The best resource i found on the Web is: hack-gpon.org

I made quite good experiences using the Lantiq based Modules (eg. from FS.com) in Ciscos ISR1k Routers, but didn't manage to get this module running in other Ciscos like C900, ISR4k or Cat8k. "Deutsche Telekom" uses the Zyxel "PMG3000-D20B" in their Small-Business All-in-one CPEs (called "Digitalisirungsbox") ... but i didn't get one of these modules running in a Cisco (even with the well-known-but-hidden CLI commands).

Nevertheless... i think creating a Business service that includes "hacky" 3rd Party GPON SFP Modules and a Cisco Router (which is always a compatibility nightmare) might not be the best idea in general. ;-) Currently we are testing all Modules we have in Junipers small SRX Boxes. Maybe i'm more successful on this way.

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