Ping IPv6?

~$ping6 fe80::20c:76ff:fe81:1
connect: Invalid argument

Huh? Silly question... how do I ping an IPv6 address in Ubuntu Hardy?
Any ideas? This does seem like a really stupid question but.....
"Invalid argument."

Is my IP address formatted incorrectly? It looks right to me.

~$ ping6 server
unknown host

Oh dear.

On Tue, 03 Jun 2008 10:27:12 +0100, Cork Soaker rearranged some electrons
to say:

> ~$ping6 fe80::20c:76ff:fe81:1
> connect: Invalid argument
>
> Huh? Silly question... how do I ping an IPv6 address in Ubuntu Hardy?
> Any ideas? This does seem like a really stupid question but.....
> "Invalid argument."
>
> Is my IP address formatted incorrectly? It looks right to me.
>
> ~$ ping6 server
> unknown host
>
> Oh dear.

What you wrote means:

fe80:0:0:0:20c:76ff:fe81:1

Is that what you meant? (ie. did you put the double colon in the right
place?)

david wrote:
> On Tue, 03 Jun 2008 10:27:12 +0100, Cork Soaker rearranged some electrons
> to say:
>
>> ~$ping6 fe80::20c:76ff:fe81:1
>> connect: Invalid argument
>>
>> Huh? Silly question... how do I ping an IPv6 address in Ubuntu Hardy?
>> Any ideas? This does seem like a really stupid question but.....
>> "Invalid argument."
>>
>> Is my IP address formatted incorrectly? It looks right to me.
>>
>> ~$ ping6 server
>> unknown host
>>
>> Oh dear.
>
> What you wrote means:
>
> fe80:0:0:0:20c:76ff:fe81:1
>
> Is that what you meant? (ie. did you put the double colon in the right
> place?)
>

Yes, that's correct. This is the IP of another machine on the same
(physically connected) network.

Hello,

Cork Soaker a écrit :
> ~$ping6 fe80::20c:76ff:fe81:1
> connect: Invalid argument

This is a "link local" address, so you must specify which interface to
use because such an address may be reachable on any interface. For the
ping6 command, use the -I option, e.g. :

$ ping6 -I eth0 fe80::20c:76ff:fe81:1

With other programs, you can use the syntax <address>%<interface> as the
destination, e.g. :

$ telnet fe80::20c:76ff:fe81:1%eth0

But it is best to use global or unique local unicast addresses.

Pascal Hambourg wrote:
> Hello,
>
> Cork Soaker a écrit :
>> ~$ping6 fe80::20c:76ff:fe81:1
>> connect: Invalid argument
>
> This is a "link local" address, so you must specify which interface to
> use because such an address may be reachable on any interface. For the
> ping6 command, use the -I option, e.g. :
>
> $ ping6 -I eth0 fe80::20c:76ff:fe81:1
>
> With other programs, you can use the syntax <address>%<interface> as the
> destination, e.g. :
>
> $ telnet fe80::20c:76ff:fe81:1%eth0
>
> But it is best to use global or unique local unicast addresses.


That's it! :-D

ping6 worked fine with %eth0 appended to the end, I'm very happy to say. :-)

I really should have figured this out from my Windows days, but alas, I
did not!

However, given that the PC only had two IPv6 addresses,
fe80::20c:76ff:fe81:1 and ::1, I would have hoped the stack would be
able to figure out where to send the ping (as the fe80 address would be
unreachable on lo).

I am, of course, aware of the problem with multiple NICs and link-local
addresses, but this shouldn't affect desktop users, and of course MID
and mobile-IPv6 users, as most will only have one network card, so maybe
this needs to be resolved before stupid Windozers start crying about the
"complexity" of Linux networking?

Thanks again Pascal.

Cork Soaker a écrit :
>
> However, given that the PC only had two IPv6 addresses,
> fe80::20c:76ff:fe81:1 and ::1, I would have hoped the stack would be
> able to figure out where to send the ping (as the fe80 address would be
> unreachable on lo).

This makes sense, but I guess the routing code in the kernel has
hardcoded that link local destinations must specify the interface,
whether the link local route in the routing table is unique or not.

> I am, of course, aware of the problem with multiple NICs and link-local
> addresses, but this shouldn't affect desktop users, and of course MID
> and mobile-IPv6 users, as most will only have one network card, so maybe
> this needs to be resolved before stupid Windozers start crying about the
> "complexity" of Linux networking?

As I wrote, my opinion is that the users should not use link local
addresses, so it not that much an issue.