Isso provavelmente se deve à configuração padrão do atributo keep_addr_on_down. Por favor, verifique isso . Você poderia testá-lo definindo esse atributo como 1 e abaixar o link novamente.
in linux/ubuntu after the link flap on an interface the global ipv6 address is flushed out & not seen in ifconfig. Any kernel patch/sysctl to retain the ipv6 address configured after the link flap.?
Also this behavior is different than ipv4 address on the same interface where the ipv4 address is retained across the link flap, any particular reason why this is the behavior for ipv6 address only.?
root@ubuntu:/home/sharb# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:0c:29:99:03:c2
inet addr:192.168.136.160 Bcast:192.168.136.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe99:3c2/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
root@ubuntu:/home/sharb# ip -6 addr add dead::1/120 dev eth0
root@ubuntu:/home/sharb# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:99:03:c2 brd ff:ff:ff:ff:ff:ff
inet 192.168.136.160/24 brd 192.168.136.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 dead::1/120 scope global
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe99:3c2/64 scope link
valid_lft forever preferred_lft forever
root@ubuntu:/home/sharb# ifconfig eth0 down
root@ubuntu:/home/sharb# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 00:0c:29:99:03:c2 brd ff:ff:ff:ff:ff:ff
inet 192.168.136.160/24 brd 192.168.136.255 scope global eth0
valid_lft forever preferred_lft forever
root@ubuntu:/home/sharb# ifconfig eth0 up
root@ubuntu:/home/sharb# ip addr show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:99:03:c2 brd ff:ff:ff:ff:ff:ff
inet 192.168.136.160/24 brd 192.168.136.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe99:3c2/64 scope link
valid_lft forever preferred_lft forever
root@ubuntu:/home/sharb# ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:0c:29:99:03:c2
inet addr:192.168.136.160 Bcast:192.168.136.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe99:3c2/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:48116 errors:0 dropped:0 overruns:0 frame:0
TX packets:13355 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:65293789 (65.2 MB) TX bytes:1052427 (1.0 MB)"