DHCPv6 CONFIRM message in Linux

user2699113 asked:

I’m testing DHCPv6 client. One of the tasks I need to check is if the CONFIRM message is sent as described in RFC (if it occurs in specified timeout). I know that this message is sent to be sure if it is still appropriate on given link.

I’d like to ask how to enforce sending such CONFIRM message by DHCPv6 client? I tried to ifconfig ethX down/up but it didn’t cause any DHCPv6 activity.

My answer:

If you are using dhclient, you will see it logged in your system logs. For example:

May 06 07:52:51 saurok dhclient[6003]: XMT: Confirm on br0, interval 1060ms.
May 06 07:52:51 saurok dhclient[6003]: RCV: Reply message on br0 from fe80::c6e9:84ff:fe6e:3eb6.
May 06 07:52:51 saurok dhclient[6003]: message status code NotOnLink.

This is the default setup on a RHEL/CentOS/Fedora system with NetworkManager.

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