Configure IPv6 addresses and perform some basic IPv6 troubleshooting.
IPv6 in Brief
IPv6 Address Format
The IPv6 address is noted as 8 groups of 16 bits (which equals 4 hexadecimal numbers), for example:
fe80:7eef:0000:0000:1000:002a:0003:0001
There are a couple of formatting rules: leading zeroes do not have to be written, and long strings of all zeroes can be summarised as ::. This would make the previous example look like:
fe80:7eef::1000:2a:3:1
Common IPv6 Addresses
The localhost address is ::1/128, which is 127.0.0.1/8 in IPv4 format.
All addresses would be ::, what is 0.0.0.0 in IPv4 format.
Multicast address is ff00::/8.
Unique Local Addresses
A unique local address is an IPv6 address in the block fc00::/7. Unique local addresses are not routable in the global IPv6 Internet.
A comparison to IPv4 would be 10.0.0.0/8 or 192.168.0.0/16 networks.
Link-local Addresses
The link-local address is automatically configured on each IPv6 interface, but does not allow for globally unique addressing.
To conform to standard /64 addressing on subnets, the actual link-local addresses are assigned with the prefix fe80::/64.
IPv6 requires a link-local address on every network interface on which the IPv6 protocol is enabled, even when routable addresses are also assigned.
Configure IPv6
Add IPv6 Address to an Existing Interface
# nmcli c NAME UUID TYPE DEVICE slave2 684ab2dc-6b40-4a50-b2b4-0450f65c4cef 802-3-ethernet enp0s8 slave1 00a5d6e6-5360-414e-8997-025fdec6d09e 802-3-ethernet enp0s17 mybond0 d021371e-5e22-4b1a-a4eb-0b96bde80702 bond mybond0
We want to add an IPv6 address fc00::10:8:8:71 to the mybond0 interface:
# nmcli c mod mybond0 ipv6.addresses fc00::10:8:8:71/7 ipv6.method manual
# nmcli c down mybond0; nmcli c up slave1; nmcli c up slave2
# ip ad show mybond0
7: mybond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
link/ether 08:00:27:ff:71:00 brd ff:ff:ff:ff:ff:ff
inet 10.8.8.71/24 brd 10.8.8.255 scope global mybond0
valid_lft forever preferred_lft forever
inet6 fc00::10:8:8:71/7 scope global
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:feff:7100/64 scope link
valid_lft forever preferred_lft forever
We see that the link-local address (scope link) is created automatically based on the network prefix fe80::/64, followed by the MAC address 08:00:27:ff:71:00 of the network card, where fffe is inserted in the middle of the MAC address part.
The unique local address (scope global) is the one that we just set up, fc00::10:8:8:71/7. We should be able to ping6 it.
# ping6 -c2 fc00::10:8:8:71 PING fc00::10:8:8:71(fc00::10:8:8:71) 56 data bytes 64 bytes from fc00::10:8:8:71: icmp_seq=1 ttl=64 time=0.037 ms 64 bytes from fc00::10:8:8:71: icmp_seq=2 ttl=64 time=0.054 ms --- fc00::10:8:8:71 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 999ms rtt min/avg/max/mdev = 0.037/0.045/0.054/0.010 ms
The link-local addresses that can be reached through interface mybond0:
# ping6 -c2 fe80::a00:27ff:feff:7100%mybond0 PING fe80::a00:27ff:feff:7100%mybond0(fe80::a00:27ff:feff:7100) 56 data bytes 64 bytes from fe80::a00:27ff:feff:7100: icmp_seq=1 ttl=64 time=0.039 ms 64 bytes from fe80::a00:27ff:feff:7100: icmp_seq=2 ttl=64 time=0.059 ms --- fe80::a00:27ff:feff:7100%mybond0 ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 999ms rtt min/avg/max/mdev = 0.039/0.049/0.059/0.010 ms
Create a New Interface with IPv6 Address
Add a new eth2 interface and assign IPv4 and IPv6 addresses:
# nmcli c add type ethernet ifname eth2 con-name eth2 \ ip4 10.8.8.90/24 gw4 10.8.8.2 \ ip6 fc00::10:8:8:90/7 gw6 fc00::10:8:8:2
We can then modify assignments later (use ipv4.gateway if on RHEL 7.2):
# nmcli c mod eth2 ipv4.addresses "10.8.8.91/24 10.8.8.2" ipv4.method manual \ ipv6.addresses "fc00::10:8:8:91/7" ipv6.method manual
Troubleshooting IPv6
Ping all nodes (multicast address) on the local network connected to the mybond0 interface:
# ping6 ff02::1%mybond0
Check IPv6 routing table:
# ip -6 ro|grep -v error fc00::/7 dev mybond0 proto kernel metric 256 fe80::/64 dev mybond0 proto kernel metric 256
what if I lost my domain name whenever I configure static ipv6 and turns the system into localhost ?
the used steps are :
#ip a
#nmcli con mod “Systemeth0” ipv6.addr fddb:fe2a:ab1e::coa8/64 ipv6.method manual
#nmcli con up “Systemeth0”
sometimes #nmcli con reload
#ping6 ipv6addr%eth0
then after rebooting the system turns into localhost.. I am seeking information for RHCE7 examination. Please help me.
In such case I would likely set a hostname by using the hostnamectl command.
Does that fine in the RH300 exam. Is that the proper way. Is there any mistakes in those commands and do I need to set the gateway for ipv6 by static but we aren’t provided with an ipv6 gateway in the exam. hostnamectl is the method I need to use ?
The hostnamectl command is a proper way of setting up a hostname. Not sure what you mean by mistakes.
In terms of a gateway, it depends, if the question asks you to configure one, then you need to do that, otherwise it should not be required. It really depends on a question.
thank you :-)
Tomorrow is my RHCE exam
Good luck with your exam!
Would you need to setup an ipv6 address if you’ve setup bonded or team interfaces?
I’d say that it depends on whether you need IPv6 or not.
during the exam i support we will be required to setup teaming on both servers,
so in this case we will be needing to setup ipv6 with the teaming feature ??
or we can setup the ipv6 separately and let the teaming run separately on ipv4.
thanks for clarification.
This information will be provided during the exam, but in essence, you need to know how to configure teaming or bonding with IPv6.
There might be a typo above:
On the line that says: “followed by the MAC address 08:00:27:ff:71:00 of the network card, where fffe is inserted in the middle of the”
Could the “fffe” be “feff”? As the address is “inet6 fe80::a00:27ff:feff:7100/64 scope link”
There is no typo, the fffe is in bold: fe80::a00:27ff:feff:7100/64.
The confusion is caused by the fact that the MAC address already contains “ff”.
A better example would be a MAC 00:11:22:33:44:55. In this case we would have:
Hi Tomas,
when I’m trying to add ipv6 on team0 and then network restart works fine, but after reboot it doesn’t. (I can’t ping fc00::7)
example:
nmcli connection modify team0 ipv6.addresses fc00::10/7 ipv6.method manual
could you please provide me with the solution.
Thanks in advance
What’s the ping error reply? Is the IPv6 address assigned to the teamed interface after the system restart?
Hi Tomas,
Here is the output:
[root@server1 ~]# ip -6 route
unreachable ::/96 dev lo metric 1024 error -113
unreachable ::ffff:0.0.0.0/96 dev lo metric 1024 error -113
fc::1 dev nm-team proto static metric 350
unreachable 2002:a00::/24 dev lo metric 1024 error -113
unreachable 2002:7f00::/24 dev lo metric 1024 error -113
unreachable 2002:a9fe::/32 dev lo metric 1024 error -113
unreachable 2002:ac10::/28 dev lo metric 1024 error -113
unreachable 2002:c0a8::/32 dev lo metric 1024 error -113
unreachable 2002:e000::/19 dev lo metric 1024 error -113
unreachable 3ffe:ffff::/32 dev lo metric 1024 error -113
fc00::/7 dev nm-team proto kernel metric 256
fe80::/64 dev nm-team proto kernel metric 256
default via fc::1 dev nm-team proto static metric 350
[root@server1 ~]#
No, IPV6 assigned before system reboot.
Thank you
This is the routing table, but what’s the ping error reply that you get?
Are you saying that after you restart the system the IPv6 address is not automatically assigned on boot?
Hi Tomas,
Here is the ping
[root@server1 ~]# ping6 fc00::10
PING fc00::10(fc00::10) 56 data bytes
From ::1 icmp_seq=1 Destination unreachable: Address unreachable
From ::1 icmp_seq=2 Destination unreachable: Address unreachable
From ::1 icmp_seq=3 Destination unreachable: Address unreachable
From ::1 icmp_seq=4 Destination unreachable: Address unreachable
From ::1 icmp_seq=5 Destination unreachable: Address unreachable
From ::1 icmp_seq=6 Destination unreachable: Address unreachable
From ::1 icmp_seq=7 Destination unreachable: Address unreachable
From ::1 icmp_seq=8 Destination unreachable: Address unreachable
^C
— fc00::10 ping statistics —
8 packets transmitted, 0 received, +8 errors, 100% packet loss, time 7003ms
after that I need to restart network, and it works, I don’t understand why.
my steps.
1. system boot
2. restart network
but why I need to restart the network? — that’s a big question for me.
Can you post the config file for the teamed interface? Are there any IPv6/network related errors in the system journal after you reboot the server?
I have a similar issue.
dmesg output :
[ 6.852644] nm-team: Port device eth2 added
[ 7.539778] IPv6: nm-team: IPv6 duplicate address fe80::a5f9:817b:cd1c:853c detected!
[ 7.713657] IPv6: nm-team: IPv6 duplicate address fc00::10:8:8:82 detected!
[ 8.510707] IPv6: nm-team: IPv6 duplicate address fe80::e0ae:3801:c62a:3c7a detected!
[ 9.123686] IPv6: nm-team: IPv6 duplicate address fe80::dc80:46f2:3d4d:abb8 detected!
ip a s output :
5: nm-team: mtu 1500 qdisc noqueue state UP qlen 1000
link/ether 8e:63:e8:f1:9b:6c brd ff:ff:ff:ff:ff:ff
inet 192.168.122.82/24 brd 192.168.122.255 scope global nm-team
valid_lft forever preferred_lft forever
inet6 fc00::10:8:8:82/7 scope global tentative dadfailed
valid_lft forever preferred_lft forever
inet6 fe80::dc80:46f2:3d4d:abb8/64 scope link tentative dadfailed
valid_lft forever preferred_lft forever
inet6 fe80::e0ae:3801:c62a:3c7a/64 scope link tentative dadfailed
valid_lft forever preferred_lft forever
inet6 fe80::a5f9:817b:cd1c:853c/64 scope link tentative dadfailed
valid_lft forever preferred_lft forever
See the last paragraph on this page:
https://www.lisenet.com/2016/configure-aggregated-network-links-on-rhel-7-bonding-and-teaming/
Hi Everyone,
I have two silly question if anyone can answer.
Question1=Copy paste not working between the server and client VM terminals in graphical mode I mean KVMS?RHEL 7
what is the option to copy and paste? please help so I could save and reduce time in RHCE exam.
Question2=is there any effect of putting SE Linux enforcing mode but don’t restart the system and make all changes to SE manage context. will the changes take place or not.
I recommend using xterm to workaround the copy/paste problem.
If you change SELinux state from “disabled” to “enforcing”, then you have to restart the system.
Hi Tomas,
If I have eth0 with IPv4 addresse + IPv4 gateway in DHCP mode:
Question 1 :
– Is it possible to do :
nmcli con mod eth0 ipv6.addresses fc00::10:8:8:71/7 ipv6.method manual ipv6.gateway fc00::10:8:8:2
– Or do I have to delete and recreate eth0 with IP4 + IP6 static addresses ?
Question 2 :
– Is it possible to have an IP4 gateway + an IP6 gateway ?
Thanks !
You can set IPv6 directly via nmcli. You can also use
GATEWAYandIPV6_DEFAULTGWon the same interface.i configure the ipv6, the gateway is not given, i use nmcli to configure ipv6.address and ipv6.method.
I tried to ping the given ip, it says “unknown host”, May I know what do i miss here?
1. eth0 IPv4 is configured, but it was set to DHCP, though the IPv4 ip is consistent, does it mean i need to change the bootproto of eth0 to non from dhcp and put the address of ipv4?
Or it will not affect the ipv6? if the eth0 bootproto is DHCP.
Thank you
Do you use ping6? IPv4 and IPv6 have their own configuration directives, one should not affect the other.