Print Page - IPv6 seems ok: ping ok, but TCP fails

Title: IPv6 seems ok: ping ok, but TCP fails
Post by: Celotoise on July 29, 2019, 10:51:50 PM

Hi,

I'm using a draytek 2925.

The he tunnel ipv6 seems ok : ping both ways are working.

But web TCP sessions fails.

Any help for fix or troubleshooting is welcome.

Title: Re: IPv6 seems ok: ping ok, but TCP fails
Post by: cholzhauer on July 30, 2019, 04:53:29 AM

Sounds like an MTU mismatch

Title: Re: IPv6 seems ok: ping ok, but TCP fails
Post by: Celotoise on July 31, 2019, 11:13:05 AM

tested multiple IPV6 MTU (1300,1442,1472..) on the windows 10 : no success

Any possibility to monitor or some stat on the traffic from HE point a view ?

Title: Re: IPv6 seems ok: ping ok, but TLS fails
Post by: Celotoise on August 01, 2019, 12:05:27 AM

More info:

from google chrome: http ok but when switching to https timeout during the tls session

Current MTU on HE is 1460

Title: Re: IPv6 seems ok: ping ok, but TCP fails
Post by: alerinaldi on October 14, 2019, 03:34:22 AM

Hello,
this is a thing that made me struggling for many hours. Finally, I discovered this is a quite well-known Broadcom chipset issue:

https://ttlexpired.co.uk/2016/02/12/ipv6-tunnel-and-failing-tcp-sessions/

If you have full control of your router, you can issue those commands to disable flow cache:

fcctl disable
fcctl config --mcast 0

Maybe your router has some GUI options to toggle those settings, too.

Title: Re: IPv6 seems ok: ping ok, but TCP fails
Post by: tullygray on March 30, 2020, 12:24:40 PM

Thanks alerinaldi, this works for me.

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Tunnelbroker.net Specific Topics => Questions & Answers => Topic started by: Celotoise on July 29, 2019, 10:51:50 PM