SEO

I am running slack9.1 on two linux boxes and I was able to use ping6
to ping one from the other across an ethernet LAN successfully.

I was also able to "ssh -6 -l user ::1" on each box to the sshd
running on the same box, but I can't ssh -6 from one box to the other.

The ssh command report the error "invalid argument"

When I run the ssh command under strace to see which system call is
failing, it turns out to be a call to connect(). It seems that some
glibc routines refuse to parse inet6 addresses?

On each box, I ran these commands:

insmod ipv6
/etc/rc.d/rc.sshd restart
ifconfig eth0

The last was to get the automatically assigned ipv6 link address on
each machine.

Any ideas what I am doing wrong?

Chris Marshall

On Fri, 22 Oct 2004 11:32:55 -0700, Chris Marshall wrote:
> I am running slack9.1 on two linux boxes and I was able to use ping6
> to ping one from the other across an ethernet LAN successfully.
>
> I was also able to "ssh -6 -l user ::1" on each box to the sshd
> running on the same box, but I can't ssh -6 from one box to the other.
>
> The ssh command report the error "invalid argument"
>
> When I run the ssh command under strace to see which system call is
> failing, it turns out to be a call to connect(). It seems that some
> glibc routines refuse to parse inet6 addresses?
>
> On each box, I ran these commands:
>
> insmod ipv6
> /etc/rc.d/rc.sshd restart
> ifconfig eth0
>
> The last was to get the automatically assigned ipv6 link address on
> each machine.

It probably only got a fe80:: (link-local) address. fe80:: are not
routable, and you probably have to specify the scope (in this case the
interface name) to get it working. So, fe80:<fill in>%eth0. But generally
speaking it is a very good idea to assign at least a site-local address to
the interface (site-local functions comparable to 192.168.0.0/255.255.0.0
in IPv4). Site-local addresses start with fec0::. An example of how to set
this up can be found in :

http://www.linuxpackages.net/howto/s...netconfig.html

It will probably work without a hassle if both interfaces have a
site-local address.

-- Daniel

Daniel de Kok <daniel@nowhere.nospam> wrote in message news:<pan.2004.10.24.08.35.30.472819@nowhere.nospa m>...
> It probably only got a fe80:: (link-local) address. fe80:: are not
> routable, and you probably have to specify the scope (in this case the
> interface name) to get it working. So, fe80:<fill in>%eth0. But generally
> speaking it is a very good idea to assign at least a site-local address to
> the interface (site-local functions comparable to 192.168.0.0/255.255.0.0
> in IPv4). Site-local addresses start with fec0::. An example of how to set
> this up can be found in :
>
> http://www.linuxpackages.net/howto/s...netconfig.html
>
> It will probably work without a hassle if both interfaces have a
> site-local address.
>
> -- Daniel

Daniel:

Thanks! That was indeed the problem. I didn't realize link local
addresses were not routable. I assigned global addresses, and then I
was able to ssh from one box to the other.

I wrote some notes to myself showing the commands I used to get this
working. For the benefit of future USENET searchers, I have appended
it below.

Chris Marshall

# some commands

# load the kernel module
insmod ipv6

# show ipv6 routes
route -A inet6

# ping a link local address residing somewhere on the LAN eth0 is
connected to
# this works from one machine to another!
ping6 -I eth0 fe80::2e0:81ff:fe10:38cd

# restart sshd with ipv6 support (meaning you restart it after the
kernel module is loaded),
# then connect to ssh using ipv6.
# this also works!
/etc/rc.d/rc.sshd restart
ssh -6 -l user ::1

# this is what doesn't work.
ssh -6 -l user fe80::2e0:81ff:fe10:38cd
# from searching the internet, I gather one problem may be that fe80
is a link local address and,
# as such, you have to specify an interface to use with it.
# ssh may not let you specify an interface.
# so, perhaps, if you could create a global address, and put a route
for it in your routing
# table, you could ssh from one machine to another.

# Ah HA!
# This lets me connect from one machine to another.
# on A:
ifconfig eth0 inet6 add 3ffe::1/64
# on B:
ifconfig eth0 inet6 add 3ffe::2/64
# on A:
ssh -6 -l user 3ffe::2
# that's because to use tcp or udp from one machine to another
requires global addresses.
# link local addresses are only for machines to discover routes, I
guess.
# I can't believe I got this working!!!