IPv6 alias do not respond from outside

[Marcelo Gondim]

Dear,

I'm having the following problem:

Host A (my network):
===================
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
options=4219b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,TSO4,WOL_MAGIC,VLAN_HWTSO>
         ether 00:1e:67:30:ea:27
         inet 186.xxx.48.3 netmask 0xffffffe0 broadcast 186.xxx.48.31
         inet6 fe80::21e:67ff:fe30:ea27%em0 prefixlen 64 scopeid 0x1
         inet6 2805:xxxx:dead::3 prefixlen 64
         inet 186.xxx.48.4 netmask 0xffffffff broadcast 186.xxx.48.4
         inet 186.xxx.48.5 netmask 0xffffffff broadcast 186.xxx.48.5
         inet6 2805:xxxx:dead::5 prefixlen 64
         inet6 2805:xxxx:dead::4 prefixlen 64
         nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
         media: Ethernet autoselect (1000baseT <full-duplex>)
         status: active

Router (Internet):
===============
vlan0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
         options=303<RXCSUM,TXCSUM,TSO4,TSO6>
         ether 00:1b:21:89:25:32
         inet 186.xxx.48.1 netmask 0xffffffe0 broadcast 186.xxx.48.31
         inet6 fe80::21b:21ff:fe89:2532%vlan0 prefixlen 64 scopeid 0x10
         inet6 2805:xxxx:dead::1 prefixlen 64
         nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
         media: Ethernet autoselect (10Gbase-SR <full-duplex>)
         status: active
         vlan: 3081 parent interface: ix0

Host B (Datacenter OVH):
======================
eth0      Link encap:Ethernet  HWaddr 00:27:0e:36:67:ae
           inet addr:91.xxx.115.215  Bcast:91.xxx.115.255 Mask:255.255.255.0
           inet6 addr: fe80::227:eff:fe36:67ae/64 Scope:Link
           inet6 addr: 2001:xxxx:1:aad7::1/64 Scope:Global
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:680611577 errors:0 dropped:115467 overruns:0 frame:0
           TX packets:410997111 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:929626301412 (865.7 GiB)  TX bytes:28858569748 (26.8 
GiB)



If I try to ping the origin Host Bto destination 2805:xxxx:dead::3, I 
get an answer correctly:

(hostb)# ping6 2805:xxxx:dead::3
PING 2805:xxxx:dead::3(2805:xxxx:dead::3) 56 data bytes
64 bytes from 2805:xxxx:dead::3: icmp_seq=1 ttl=55 time=219 ms
64 bytes from 2805:xxxx:dead::3: icmp_seq=2 ttl=55 time=218 ms
64 bytes from 2805:xxxx:dead::3: icmp_seq=3 ttl=55 time=219 ms
64 bytes from 2805:xxxx:dead::3: icmp_seq=4 ttl=55 time=218 ms

But it does not ping 2805:xxxx:dead::4 and 2805:xxxx:dead::5:

(hostb)# ping6 2805:xxxx:dead::4
PING 2805:xxxx:dead::4(2805:xxxx:dead::4) 56 data bytes
 From 2001:xxxx:2001:1001::96 icmp_seq=2 Destination unreachable: 
Address unreachable
 From 2001:xxxx:2001:1001::96 icmp_seq=8 Destination unreachable: 
Address unreachable

Now if I do a ping from the router to Host A, it goes to work:

(router)# ping6 2805:xxxx:dead::4
PING6(56=40+8+8 bytes) 2805:xxxx:dead::1 --> 2805:xxxx:dead::4
16 bytes from 2805:xxxx:dead::4, icmp_seq=0 hlim=64 time=13.550 ms
16 bytes from 2805:xxxx:dead::4, icmp_seq=1 hlim=64 time=7.776 ms

(hostb)# ping6 2805:xxxx:dead::4
PING 2805:xxxx:dead::4(2805:xxxx:dead::4) 56 data bytes
64 bytes from 2805:xxxx:dead::4: icmp_seq=1 ttl=56 time=219 ms
64 bytes from 2805:xxxx:dead::4: icmp_seq=2 ttl=56 time=218 ms
64 bytes from 2805:xxxx:dead::4: icmp_seq=3 ttl=56 time=219 ms

Why work now?

FreeBSD xxxxx 10.0-STABLE FreeBSD 10.0-STABLE #10 r267839: Thu Jul 10 
15:35:04 BRT 2014 root at xxxxx:/usr/obj/usr/src/sys/GONDIM  amd64

Thanks and best regards,
Gondim