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I have a server that I can connect via SSH over IPv4 address. Now I want to SSH over IPv6.

I'm sure that my server is assigned with a valid IPv6 address, and I've configured sshd to listen on v6 address (I set it to [::]:311), but when I run (on my laptop)

ssh -v -6 -p 311 PUBLIC_V6_IP -l same_user_as_v4 -i ~/.ssh/id_rsa

I got the following output:

OpenSSH_5.8p2, OpenSSL 1.0.0d 8 Feb 2011
debug1: Reading configuration data /home/winus/.ssh/config
debug1: Applying options for *
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to PUBLIC_V6_IP [PUBLIC_V6_IP] port 311.
debug1: connect to address PUBLIC_V6_IP port 311: Permission denied
ssh: connect to host PUBLIC_V6_IP port 311: Permission denied

Some extra info:

  1. My laptop is running Arch Linux, while my server is Ubuntu Server 10.10
  2. sshd -V on the server shows OpenSSH_5.5p1 Debian-4ubuntu5, OpenSSL 0.9.8o 01 Jun 2010
  3. ssh -V on my laptop shows OpenSSH_5.8p2, OpenSSL 1.0.0d 8 Feb 2011
  4. ssh -6 ::1 on my laptop is OK.
  5. ping6 PUBLIC_V6_IP is OK.
  6. ssh -6 ::1 -p 311 on the server is OK.
  7. ssh -6 PUBLIC_V6_IP -p 311 on the server is also OK.

Question: Anyone knows what's going on?

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Can you do strace -o log.txt -e network ssh -6 PUBLIC_V6_IP true, then check for "EPERM" in log.txt? –  grawity May 13 '11 at 13:07
    
@grawity I paste the output here - I didn't find EPERM in it... –  E.T May 13 '11 at 20:24
    
Oh, it's EACCESS, not EPERM :( (It's present on the last line.) –  grawity May 14 '11 at 14:03
    
I can't connect to the addres in the link on port 311, and I have otherwise working IPv6. –  Turbo J May 14 '11 at 14:24
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1 Answer

Possible causes could be:

  • Local firewall (ip6tables)

  • External firewall on your network (according to some sources, ICMPv6 "Administratively prohibited" error message is interpreted by Linux as EACCESS)

  • AppArmor, SELinux, Smack (although neither of them is on by default on Arch)

Things you could try:

  • reset ip6tables rules

  • connect to the server using other programs (socat stdio tcp:[2604:....]:311) and see if they return the same message; test with both same and different ports

  • ping6, traceroute6, and see if any hop returns "Administratively prohibited" or any other error

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