Adcantage to using IPv6 on Linode?

At this point, it does not make sense to switch off IPv4 and only run on IPv6. Your best bet is to turn on IPv6 alongside IPv4, allowing access over both protocols.

You may need to reconfigure some of the daemons you mentioned to bind to both your v4 and v6 addresses. You will also need to configure any firewall rules you have separately (iptables vs ip6tables).

The point of enabling IPv6 now is to ensure all of your services are working as expected and iron out any bugs you encounter. IPv4 exhaustion may not be causing problems at this exact moment, but we know what the failure modes are going to look like. If you take the time now to learn and prepare, your services will be IPv6 ready while your peers will be panicking.

True, preparation is good. I think I'll do just that.

I thought I was going to be "forced" to switch completely to IPv6 since I wasn't reading the Manager page right… I need to open my eyes ;-)

I suppose the next question is: Since I don't have an IPv6 connection to test from (not even another Linode, nor any cohorts that have an IPv6 connection), how would I test the new configuration?

Hit up Hurricane Electric's Tunnel Broker and get IPv6 going at home. (There are other tunnel providers, but I've had the best experience with HE.)

@Piki:

I suppose the next question is: Since I don't have an IPv6 connection to test from (not even another Linode, nor any cohorts that have an IPv6 connection), how would I test the new configuration?
You can test you have IPv6 connectivity by using ping6 to an address with AAAA records

eg

% ping6 www.ip6test.com
PING www.ip6test.com(ns1.ip6test.com) 56 data bytes
64 bytes from ns1.ip6test.com: icmp_seq=0 ttl=52 time=154 ms
64 bytes from ns1.ip6test.com: icmp_seq=1 ttl=52 time=153 ms
64 bytes from ns1.ip6test.com: icmp_seq=2 ttl=52 time=153 ms
64 bytes from ns1.ip6test.com: icmp_seq=3 ttl=52 time=153 ms
64 bytes from ns1.ip6test.com: icmp_seq=4 ttl=52 time=153 ms
^C
--- www.ip6test.com ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4003ms
rtt min/avg/max/mdev = 153.525/153.828/154.116/0.473 ms, pipe 2

ping6 only uses IPv6 so if it works then you have connectivity :-)

The website at http://www.ip6test.com/ can also do some server level testing; I've never tried it, though.

You can also ask someone else with IPv6 connectivity to test things out. I'm usually more than happy to try hitting web, mail, etc servers via IPv6 from a "known good" connection.

It doesn't address this situation, but the turtle on http://www.kame.net/ will dance if you're using IPv6. I have an easter egg on http://hoopycat.com/ as well, but that's a less-official test. :-)

(http://test-ipv6.com/ and the top of http://www.opendns.com/ are two other useful resources, neither of which will help you test your server.)

… and I almost forgot to chime in on the original question :-)

Why do I consider IPv6 to be a requirement? Being able to directly communicate between any and all of my servers/workstations irregardless of location is important to me. I should be able to securely and efficiently access the same resources whether I am sitting at my workstation, logged into my Linode or using my netbook on the bus, without having to do strange tricks with bastion hosts or port forwarding.

In other words, imagine a global, ubiquitous network where each computer has a unique, public IP address, and there is no NAT. That's the IPv6 Internet (minus the ubiquitous part…). It's not quite as awesome as a world without war and hunger, but the magnitude is roughly the same. (If John Lennon were alive today…)

Also, at least with Linode, all Linodes within a datacenter are within the same address range. This means the private network trick for unmetered data transfer isn't necessary, so the same IP address can be used for inter- and intra-datacenter traffic. Good stuff.