Originally Posted by sulekha
I gave the folowing command
ip addr show eth0
to get the o/p as
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:80:ad:83:e4:75 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.17/24 brd 192.168.0.255 scope global eth0
inet6 fe80::280:adff:fe83:e475/64 scope link
valid_lft forever preferred_lft forever
now my question is what does valid_lft forever preferred_lft forever means ???
You don't provide all the details (version/distro of Linux? Are you using IPv6? Goals/problems?), but Google turns up lots of answers.
valid_lft = Valid Lifetime
preferred_lft = Preferred Lifetime
Read RFC 3484 "Default Address Selection for Internet Protocol version 6 (IPv6)".
In the case of a tie (ie., source address not decided by destination subnet or other mechanisms), if you have multiple IPv6 addresses on an interface, linux tends to use the last address added.