netflix OCA in a CG-NAT world

Dave Temkin dave at
Mon Nov 26 05:09:53 UTC 2018

Not exactly. You don't need to advertise the RFC1918 to the OCA - just make
sure you advertise the CGN prefix to it, and make sure that the OCA's
default gateway knows how to reach the RFC1918 clients. So long as the
"outside" IP of your CGN is advertised to the OCA (the IP that clients who
would be using the OCA would appear to the internet as) it should work.


On Mon, Nov 26, 2018 at 1:04 PM Aaron1 <aaron1 at> wrote:

> Thanks Dave, so my local OCA will listen to my BGP advertisements for
> RFC1918 prefixes if I decided to advertise them?
> Aaron
> On Nov 25, 2018, at 10:47 PM, Dave Temkin <dave at> wrote:
> FWIW (reviving an old thread)-
> Putting an OCA with bypass through the CGN with RFC1918 space will
> actually work just fine. We (Netflix) don't formally support it because of
> the vast number of non-standard CGN implementations out there, but if your
> clients are in RFC1918 space and the next hop router from the OCA knows how
> to reach them, it will just work. We only use BGP to inform our control
> plane, not for local routing. Any traffic not served via the OCA will go
> through CGN as usual and out peering/transit. Note that it does complicate
> troubleshooting for both sides.
> And yes, IPv6 is fully supported by every piece of our infrastructure; the
> issue is TVs and STBs that do not support v6 - but we have finally seen the
> largest device manufacturers commit to supporting it (if they don't already
> on their late model sets) so that should change year over year.
> -Dave
> On Mon, Sep 17, 2018 at 11:52 PM Jared Mauch <jared at>
> wrote:
>> > On Sep 17, 2018, at 6:54 AM, Tom Ammon <thomasammon at> wrote:
>> >
>> > I'm looking to understand the impact of CG-NAT on a set of netflix
>> OCAs, in an ISP environment. I see in Netflix's FAQ on the subject that
>> traffic sourced from RFC 1918/6598 endpoints can't be delivered to the OCA.
>> Is this simply a matter of deploying the OCA on the outside of the CGN
>> layer? What are the other consequences of CGN upon the OCA?
>> >
>> Yes, you want to deploy it outside your CG-NAT.
>> I also strongly suggest you look at how to get native IPv6 from your
>> clients behind the CG-NAT rolled out.  I know many folks have had issues
>> with various CDNs and the number of devices that reach out.  This is why
>> folks get the Google captcha, etc.
>> Giving those end-users an alternate way out will help.  I understand this
>> may take effort and is harder for folks using UBNT & Tik gear in a smaller
>> environment, but there is value for your end-users.
>> - Jared
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