Disabling IPv6

[#1]

In a recent Predictive Cluster Validation Summary for one of my clusters, Cloudera Proactive Support states:

"The following hosts have IPv6 enabled, which is against our best practices, because it can cause connectivity problems. This is discussed in the CDH documentation. (http://www.cloudera.com/content/cloudera/en/documentation/core/latest/topics/cdh_ig_req_supported_ve..."

Yet that page simply says that "IPv6 is not supported and must be disabled."

If this is a hard requirement, then why is there no documentation on *how* to disable IPv6 for the various supported OSs?  I understand that Cloudera may not want to get into the OS configuration business, but at least pointers to vender documentation should be provided.

[#2]

Hello @mjarnold,

Thank you for pointing that out.  I have added this post to internal Cloudera Jira DOCS-1862 where we are discussing documentation.

Regards,

Ben

[#3]

Thank you Ben.

[#4]

Hey @bgooley,

Is there any update on DOCS-1862?

[#5 · Accepted solution]

Hi @mjarnold, I can comment on this on behalf of Ben. The docs received a minor improvement that advises the OS vendor to be contacted for complete information or any necessary assistance regarding disabling ipv6:

Networking Protocols Support
CDH requires IPv4. IPv6 is not supported and must be disabled.
Note: Contact your OS vendor for help disabling IPv6.

This was the resulting improvement in the docs stemming from the jira I filed after we first spoke about this issue. I know this isn’t much of a change, but we felt it was the most sound advice we could provide on the next-steps necessary.

If you have any feedback please do let us know. We sincerely appreciate your long-running excellent partnership here with us in Cloudera Support.

Best,
Alex

[#6]

@Alex,

I am curious as to what the Proactive Support tests look for when testing whether IPv6 is enabled.  Is it the existence of IPv6 addresses on interfaces or the presence of the IPv6 kernel module?

Red Hat's solutions indicate that you can either disable the kernel module via kernel boot options (results in other things breaking) or disable IPv6 on network interfaces via sysctl.  Debian appears to be similar.

[#7]

Hi Michael,

Based on what I see in the script/code, it's the presence of inet6 in the ifconfig output, which is included in the diagnostic bundle. If inet6 is present and in use, I believe that's the basis for the alert that was issued.

Best,

Alex

[#8]

Thanks.  It sounds like the following should suffice:

sysctl -w net.ipv6.conf.all.disable_ipv6=1

sysctl -w net.ipv6.conf.default.disable_ipv6=1

[#9]

Completely agreed sir. +1

[#10]

And to fully answer myself, here are the links to vendor documentation:

Red Hat/CentOS

https://access.redhat.com/solutions/8709

https://wiki.centos.org/FAQ/CentOS7#head-8984faf811faccca74c7bcdd74de7467f2fcd8ee
https://wiki.centos.org/FAQ/CentOS6#head-d47139912868bcb9d754441ecb6a8a10d41781df

Debian/Ubuntu

https://wiki.debian.org/DebianIPv6#How_to_turn_off_IPv6

https://wiki.ubuntu.com/IPv6#Disabling_IPv6

Suse

https://www.suse.com/support/kb/doc.php?id=7015035

https://www.suse.com/support/kb/doc/?id=7012111