[CentOS] Diagnosing IPv6 routing

Thu Apr 30 22:44:40 UTC 2020
Kenneth Porter <shiva at sewingwitch.com>

--On Thursday, April 30, 2020 6:08 PM -0500 Chris Adams <linux at cmadams.net> 

> From your traceroutes, it kind of looks like it's possible that it's
> something on your gateway (but I'm not really sure).  Do you have any
> IPv6 firewall running there?

I dropped the firewall just to make sure it wasn't the issue. My 
connections to Linode eventually started working. Comparison to the 
traceroute I posted earlier shows a different router just before my server, 
so I suspect they had a bad router. I still can't connect the other way, 
towards AT&T. But routing must be working because replies from outbound 
connections are getting back. I'd file a ticket with AT&T but they still 
haven't added my account to their ticket system after more than a week of 
service. So I'm stuck playing tag with the sales consultants.

> One other note about mail on v6 - not only do you need to have a valid
> reverse (with matching forward) DNS record, you probably need to do TLS
> with a valid cert (Let's Encrypt is free and easy).

Thanks for reminding me. I added an IPv6-only name for testing and for my 
reverse and need to add that to my certificate.