[AusNOG] VPNs over Telstra wireless broadband

[James Andrewartha]

On Fri, 15 Mar 2024, James Andrewartha wrote:

> On Thu, 14 Mar 2024, Craig Askings wrote:
> 
> > Are you using an ip address or FQDN as the vpn target for the students to connect to?
> 
> FQDN.
> 
> I've turned on keepalive but there's no timer setting available.

A parent brought their modem into the school for testing, and it already 
had PDP set to IPv4v6 and had a RFC6598 address, so it wasn't that. The 
problem was actually MTU - on testing, pings could get through, and the 
initial stages of a web connection, but the data never made it back from 
the server to the client. So I set the VPN interface MTU to 1280 and 
everything started working. Testing the raw connection showed an MTU of 
1330 which is an odd value. Is there anyone from Telstra who can confirm 
that the 5G home broadband product has a lower MTU?

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