Enable ipv6 on centos PPPoE unifi

ref: http://wandin.net/dotclear/index.php?post/2011/02/10/Native-IPv6-with-Internode-and-CentOS

Note: you will need new BTU from unifi technician that support ipv6. old btu does not support ipv6 at my place.

remember to put ipv6[space],

# vi /etc/ppp/options 
lock
ipv6 ,

May  5 15:24:46 backup pppd[15296]: PAP authentication succeeded
May  5 15:24:46 backup pppd[15296]: local  LL address fe80::78e0:xxxx:xxxx:xxxx
May  5 15:24:46 backup pppd[15296]: remote LL address fe80::2a6e::xxxx:xxxx:xxx
May  5 15:24:46 backup pppd[15296]: local  IP address 175.143.xx.xx
May  5 15:24:46 backup pppd[15296]: remote IP address 175.143.xx.xx