Skip to content

Testing Software with IPv6

About this Document

This document provides instructions on setting up a host with an IPv6 address for testing the OSG software stack. The plan is to be able to spin up special Fermicloud VM’s that have corresponding public IPv6 addresses meaning that there will be a limit of ~15 VM’s at one time.

For more information on IPv6, consult Wikipedia.


  1. Be familiar with your institute's network policy and firewall configuration 1 Root access is required to configure iptables

Enabling IPV6

  1. Determine the public IPv6 address of your host. In the example below that would be 2001:400:2410:29::182:

    user@host $ nslookup -type=aaaa <HOSTNAME>
    Non-authoritative answer:  has AAAA address 2001:400:2410:29::182

    Replacing <HOSTNAME> with your machine's hostname.

  2. Ask your network administrator for your IPv6 default gateway

  3. Modify /etc/sysconfig/network-scripts/ifcfg-eth0 and be sure these lines exist, and :

    IPV6_DEFAULTGW="The IPV6 Default Gateway"

    Replace <IPV6 ADDRESS> with the address found in step 1.

  4. Restart the network devices:

    root@host # service network restart
    Shutting down interface eth0:                              [  OK  ]
    Shutting down loopback interface:                          [  OK  ]
    Bringing up loopback interface:                            [  OK  ]
    Bringing up interface eth0:                                [  OK  ]

Testing IPv6 connectivity

To verify that the VM is capable of IPv6 we will be using the ping6 command between the test VM and another IPv6 capable machine

  1. From another IPv6 capable machine, ping your VM:

    user@host $ ping6
    PING 56 data bytes
    64 bytes from icmp_seq=1 ttl=51 time=68.1 ms
    64 bytes from icmp_seq=2 ttl=51 time=57.6 ms
  2. From your test VM, ping another IPv6 capable machine:

    [efajardo@ipv6vm001 ~]# ping6
    PING 56 data bytes
    64 bytes from icmp_seq=1 ttl=51 time=57.6 ms

Verifying SSH over IPv6

Make sure you can login to your VM over IPv6. Currently, Fermilab's kerberos does not support SSH over IPv6.

  1. Add your ssh_key to your machine and make sure /etc/ssh/sshd_config has the following lines:

    RSAAuthentication yes
    PubkeyAuthentication yes
  2. Try connecting to you IPv6 enabled machine over SSH:

    efajardo@uaf-4 ~$ ssh -6 [email protected]
    Last login: Wed Jun 11 14:51:47 2014 from 2607:f720:1700:1b30:21f:c6ff:feeb:2631
    [root@ipv6vm001 ~]#

Disabling IPv4

If you were able to log into your VM over IPv6, you can disable IPv4 and try to communicate exclusively over IPv6.

  1. Comment the IPADDR line in /etc/sysconfig/network-scripts/ifcfg-eth0:



    Ensure that your IPV6ADDR is uncommented otherwise you will not be able to connect to the host again

  2. Restart the network services:

    root@host # service network restart
  3. The ping command should no longer work:

    root@host # ping
    PING ( 56 data bytes
    Request timeout for icmp_seq 0
    Request timeout for icmp_seq 1

Disabling IPv6

In your testing, you may find the need to disable IPv6.

root@host # sysctl -w net.ipv6.conf.all.disable_ipv6=1
root@host # service network restart

The ping6 command should no longer work:

root@host # ping6
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1

Testing in mixed mode

To test IPv6 in mixed mode, you can use the ntop tool to monitor traffic over IPv6. ntop is installed on all the test machines and you can access the web interface at hostname:3000. To see a table that displays network traffic between your VM and another host by going to All Protocols -> Traffic and looking at the IPv6 column.


Enforcing communication over IPv6

If you want to enforce IPv6 over mixed mode you can try using the IPv6 address for whatever software that you are testing. For example with xrdcp:

root@host # xrdcp -d 1 /tmp/first_test root://[2607:f720:1700:1b30::a4]:1094//tmp/first_test_8

Notice that the IPv6 address follows RFC2732.