T-Mobile 4G/5G CGNAT vs WireGuard tunnel jitter

[Lonnie Abelbeck]

> On Apr 10, 2021, at 11:12 AM, Lonnie Abelbeck <lists at lonnie.abelbeck.com> wrote:
> 
>> On Apr 10, 2021, at 10:59 AM, Roman Mamedov <rm at romanrm.net> wrote:
>> 
>> On Sat, 10 Apr 2021 10:27:23 -0500
>> Lonnie Abelbeck <lists at lonnie.abelbeck.com> wrote:
>> 
>>> I have been testing the T-Mobile Home Internet (4G/5G fixed wireless) service to a Linode VM via WireGuard.
>>> 
>>> The TMHI service uses CGNAT plus an additional NAT in their modem/gateway with a MTU of 1420, so WireGuard is configured with a 1340 MTU.
>> 
>> Do they provide IPv6? I see mentions that yes, but with incoming connections
>> blocked. Might still work for WG.
> 
> Hi Roman,
> 
> TMHI uses IPv6 for their CGNAT, but AFAIK their current firmware does not support IPv6 on the ethernet ports (I disable their WiFi).
> 
> But if (when) they support IPv6, establishing the WireGuard tunnel over IPv6 would be great, and back to a 1420 MTU for WireGuard.

A quick update, TMHI does support IPv6 via DHCPv6, but sadly has the same MTU (1420) as IPv4 has, and IPv6 is firewalled inbound (as Roman said).

I now have the WireGuard transport endpoints using IPv6 over TMHI, but the jitter with low bitrate traffic still occurs as with the IPv4 transport endpoint setup.  Other than that, it works quite well.

Lonnie