$ sudo dhclient -v -6
[sudo] password for [user]: [entered]
Internet Systems Consortium DHCP Client 4.3.1
Copyright 2004-2014 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on Socket/eth0
Sending on Socket/eth0
PRC: Confirming active lease (INIT-REBOOT).
XMT: Forming Confirm, 0 ms elapsed.
XMT: X-- IA_NA 5a:bf:89:f6
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::a:ffc8
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::1:9998
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120:10:250:0:ffc8
XMT: V IA_NA appended.
XMT: Confirm on eth0, interval 1050ms.
XMT: Forming Confirm, 1050 ms elapsed.
XMT: X-- IA_NA 5a:bf:89:f6
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::a:ffc8
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::1:9998
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120:10:250:0:ffc8
XMT: V IA_NA appended.
XMT: Confirm on eth0, interval 2140ms.
XMT: Forming Confirm, 3190 ms elapsed.
XMT: X-- IA_NA 5a:bf:89:f6
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::a:ffc8
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::1:9998
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120:10:250:0:ffc8
XMT: V IA_NA appended.
XMT: Confirm on eth0, interval 3980ms.
XMT: Forming Confirm, 7170 ms elapsed.
XMT: X-- IA_NA 5a:bf:89:f6
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::a:ffc8
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120::1:9998
XMT: | X-- Confirm Address fd57:a10a:9ec2:5120:10:250:0:ffc8
XMT: V IA_NA appended.
XMT: Confirm on eth0, interval 2830ms.
Max retransmission duration exceeded.
PRC: Bound to lease 00:01:00:01:1c:25:13:f1:00:0d:b9:34:27:84.
/sbin/dhclient-script: 55: /sbin/dhclient-script: shopt: not found
/sbin/dhclient-script: 60: /sbin/dhclient-script: [[: not found
/sbin/dhclient-script: 68: /sbin/dhclient-script: shopt: not found
/sbin/dhclient-script: 55: /sbin/dhclient-script: shopt: not found
/sbin/dhclient-script: 60: /sbin/dhclient-script: [[: not found
/sbin/dhclient-script: 68: /sbin/dhclient-script: shopt: not found
/sbin/dhclient-script: 55: /sbin/dhclient-script: shopt: not found
/sbin/dhclient-script: 60: /sbin/dhclient-script: [[: not found
/sbin/dhclient-script: 68: /sbin/dhclient-script: shopt: not found