ipv6 question

I suppose I took/take the view that it *is*, in a sense, being used for

The network is a training network, isolated from the Internet, and used
for demonstration purposes. It's a good way to engrave the doco prefix
in the students' minds. It also allows all the slides, exercises and
other documentation to use the documentation prefix and yet directly
match the demonstration network.

ULA prefixes have little internal logic and are hard to remember. Not a
problem in production, but just another barrier in a training
environment. "2001:db8::/32" is very easy to remember (I guess that's
the point) and easy to add easy-to-use subnets into.

However, I do appreciate that it's a bit of an edge case. In my training
I specifically draw the students' attention to this fact.

Thanks, K.


Then I won't use this ipv6 address 2001:db8:cafe:1111::12 for test

Acutually, I have one in eth0 when I run ifconfig -a

          inet6 addr: fe80::20c:29ff:fe3c:92a1/64 Scope:Link

but I also can't ping it

ping6 fe80::20c:29ff:fe3c:92a1
connect: Invalid argument

but ping6 ::1 is fine

ping6 ::1
PING ::1(::1) 56 data bytes
64 bytes from ::1: icmp_seq=0 ttl=64 time=7.18 ms
64 bytes from ::1: icmp_seq=1 ttl=64 time=0.050 ms

inet6 addr: fe80::20c:29ff:fe3c:92a1/64 Scope:Link

This is a link level address, only valid on one interface. So you need to look
at which interface it is attached to in the ifconfig output.

ping6 fe80::20c:29ff:fe3c:92a1
connect: Invalid argument

ping6 wants the interface name for link-scope addresses, because on some
hardware setups, the same MAC is used for all interfaces, which means that
each interface has the same link-scope address. So to disambiguate it,
you have to feed it the interface name so it knows which link to use.

On my laptop, I currently have:

wlan0 Link encap:Ethernet HWaddr 00:24:D6:53:C5:BA
  inet6 addr: fe80::224:d6ff:fe53:c5ba/64 Scope:Link

% ping fe80::224:d6ff:fe53:c5ba%wlan0
ping6 fe80::224:d6ff:fe53:c5ba%wlan0
PING fe80::224:d6ff:fe53:c5ba%wlan0(fe80::224:d6ff:fe53:c5ba) 56 data bytes
64 bytes from fe80::224:d6ff:fe53:c5ba: icmp_seq=1 ttl=64 time=0.072 ms
64 bytes from fe80::224:d6ff:fe53:c5ba: icmp_seq=2 ttl=255 time=0.081 ms
64 bytes from fe80::224:d6ff:fe53:c5ba: icmp_seq=3 ttl=255 time=0.090 ms
--- fe80::224:d6ff:fe53:c5ba%wlan0 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.072/0.081/0.090/0.007 ms


Thank you. I try your way. the ipv6 address is on eth0 interface.

I try to run ping6 the fe80::20c:29ff:fe3c:92a1%eth0

lt is same problem!

Any idea?

Thank you

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:3c:92:a1 brd ff:ff:ff:ff:ff:ff
    inet brd scope global eth0
    inet6 fe80::20c:29ff:fe3c:92a1/64 scope link tentative
       valid_lft forever preferred_lft forever

# ping6 fe80::20c:29ff:fe3c:92a1
connect: Invalid argument
# ping6 fe80::20c:29ff:fe3c:92a1%eth0
connect: Invalid argument

Try ping6 -I eth0 fe80::20c:29ff:fe3c:92a1


What is this meaning?

ping6 -l eth0 fe80::20c:29ff:fe3c:92a1
ping: bad preload value, should be 1..65536

Thank you

That was a capital "i" not a lower case "L". man ping6

Hi Jason

Thank you. Can I know what is wrong?

ping6 -I eth0 fe80::20c:29ff:fe3c:92a1
connect: Cannot assign requested address

Thank you

Maybe duplicate address detection? Are you statically assigning this address? Have you checked your kernel log?