we've disabled ipv6 via ipv6.disable=1 in grub in 3363.19+ linux stemcells some time ago. in previous stemcells it was disabled via sysctl at bootup.
we are now aware that small number of releases may be affected (one release for example was disabling portion of ipv6 functionality themselves but no longer can succeed since /proc/... entry is gone and that code was not checking for its existence). we also had a report that some java processes may be affected if they were using particular libraries that for some reason try to obtain local ipv6 address (even though ipv6 was disabled before their startup).
we try very hard to avoid making any breaking changes in minor stemcell versions; however, this changed turned out to be more disruptive than we expected. given that it affects only small number of releases we have decided to keep it in (hoping that it should be easy for release authors to issue a patch if necessary).
(for folks thinking about the future ipv6 support, bosh-agent will automatically turn it on at runtime if necessary.)
as usual feel free to reach out to us on #bosh slack if you need any help.
