> 1) When was the last time you fixed networking issues by turning on IPv6?
I've used IPv6 to help users behind CGNAT; enabling IPv6 for client -> server often means those clients no longer go through carrier stateful firewalls and their sometimes tragically low idle timeouts (I've seen timeouts as low as 10 seconds).
I've also used IPv6 to help in a proxy config when I couldn't get the upstream servers configured for more listening ports; it's super easy to get extra v6 source addresses for the proxy servers and harder to get v4 addresses. With high volumes and low session times, you run into port reuse issues at around 10k-20k sessions per {source ip, dest ip, dest port} tuple; theoretically you can get to 64k, but TIME_WAIT takes time to clear and you don't want to be too aggressive.
Probably less going forward, but v6 and v4 often have different routed paths, and sometimes you want to get off of one path and onto another. If you're using a tunneled v6 connection, you almost certainly have a different path for most destinations.
> 2) When was the last time you fixed networking issues by turning off IPv6?
My previous DSL modem would crash when receiving fragmented IPv6 packets. My current one doesn't crash, but adds a lot of internal latency. Temporarily fixed by disabling IPv6; permanently fixed by using the modem in bridge mode and doing PPPoE on my own personal equipment (at great cost to my own sanity, PPPoE is gross, and I built a multi-node redundancy setup, so PPPoE sessions can be transferred between my redundant routers, bleh)
I've used IPv6 to help users behind CGNAT; enabling IPv6 for client -> server often means those clients no longer go through carrier stateful firewalls and their sometimes tragically low idle timeouts (I've seen timeouts as low as 10 seconds).
I've also used IPv6 to help in a proxy config when I couldn't get the upstream servers configured for more listening ports; it's super easy to get extra v6 source addresses for the proxy servers and harder to get v4 addresses. With high volumes and low session times, you run into port reuse issues at around 10k-20k sessions per {source ip, dest ip, dest port} tuple; theoretically you can get to 64k, but TIME_WAIT takes time to clear and you don't want to be too aggressive.
Probably less going forward, but v6 and v4 often have different routed paths, and sometimes you want to get off of one path and onto another. If you're using a tunneled v6 connection, you almost certainly have a different path for most destinations.
> 2) When was the last time you fixed networking issues by turning off IPv6?
My previous DSL modem would crash when receiving fragmented IPv6 packets. My current one doesn't crash, but adds a lot of internal latency. Temporarily fixed by disabling IPv6; permanently fixed by using the modem in bridge mode and doing PPPoE on my own personal equipment (at great cost to my own sanity, PPPoE is gross, and I built a multi-node redundancy setup, so PPPoE sessions can be transferred between my redundant routers, bleh)