Keith's Personal Blog

OK So it seems that if you have both IPV4 and IPV6 transit, for some reason SSH prefers IPV6 transit, over IPV4.

Im not sure why this is, perhaps its because IPV6 is meant to supercede IPV4, whatever the reason, this causes lag when using SSH, primarily due to the lack of capable IPV6 upstream providers, until this situation improves, there's a simple change you can do in order to force ssh to use IPV4 first!.

Add the following to ssh_config (/etc/ssh/ssh_config or /etc/ssh_config).

AddressFamily inet

This forces ssh to use IPV4 by default instead of v6, whilst maintaining the ability to connect to ssh capable ipv6 hosts.

Note: Any preference over v4/v6 specified in your ssh command (e.g. ssh -6 user@host) will override this setting.

Enjoy.