Comcast enables 6to4 relays

Jack Bates jbates at
Mon Aug 30 21:44:11 UTC 2010

Franck Martin wrote:
> Is there a list of 6to4 relays?
> I'm curious.
> Also, I'm also curious to know if ISPs in Europe (which are more advanced in IPv6 deployment) have experienced the same issues?

Sprint has one which is absolutely horrible (or was a year or two ago). 
I'd recommend any and every ISP to setup a 6to4, even if it runs over a 
v6 tunnel to HE. Accidentally getting one from someone else can give you 
exceptionally broken 6to4 connectivity. Being anycast, I'd say 
routeviews might be a good place to check for some, but often times they 
are hidden within the networks they serve.

That being said, 6to4 itself is often horrible. It works fine if you are 
talking 6to4 direct to the remote site (vs using a relay), but relays 
often break and are hard to troubleshoot due to their nature.

In the last year, my 6to4 tunnel has peaked at 6.44mb/s (1day average) 
but more common peaks are 150-250kb/s (5min average).

My tunnel to was running 4-8 times that including the 6to4 relay 
serving all my customers + native traffic for 15 hosts and 2 servers. 
It's hard to get accurate on recent traffic loads as much of my v6 
traffic shifted to dual stacked peers and I don't have a method of 
separating the v4/v6 traffic in the graphs (me thinks it's time to test 
ipv6 over mpls).


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