option 212 for 6RD

Jean-Francois.TremblayING at videotron.com Jean-Francois.TremblayING at videotron.com
Mon Jan 14 21:49:52 CET 2013

> > The only recent issue we hit what with a specific brand of home 
> > that auto-detects native IPv6 vs 6RD. In some cases, they forget to 
> > lower the IPv6 MTU in RAs to 1480. This issue will be fixed in their 
> > future release. Leaving the LAN MTU at 1500 with 6RD causes PMTUD 
> > problems with many content providers, especially YouTube, who doesn't 
> > seem to process ICMP too bigs properly.
> It would really help if you could share more specifics on this.
Have a look at these threads: 

Linksys also does 6RD "autodetection" I believe. Most of their routers
lower the MTU to 1480, with the notable exception of the E4200v1 (which 
is not autodetect, so less of a problem). 

> > I'd say you're safe enabling it, but be aware that you may get a few 
> > support call from people having "YouTube problems" on the short term.
> If I knew the ethernet address prefix of this vendor we could perhaps 
> blacklist that one from getting the option 212 response?

This is one way out, it could help with the problem. But these routers
also offer to "copy your PC's MAC address" in the initial wizard. So 
a number of them show up with a MAC different from the router vendor. 


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