Setup IPv6 on CentOS 7 in a ESXi-VM by OVH

Question

Yesterday i orderd a new dedicated server at OVH for a small network with virtual machines powered by ESXi.

Today i created my first VM with CentOS 7 that works fine so far. I'm able to ping Google with IPv4, but i can not get the IPv6-Connectivity to work.

My Configuration (Guest):

Device: ens160
IP: 145.239.XXX.XX/32
Netmask: 255.255.255.255
Gateway: 217.182.XXX.254 (Host)
----
IPv6: 2001:41d0:700:XXX:x
Netmask: 64
Gateway: 2001:41d0:700:XXff:ff:ff:ff:ff (as suggested by OVH)

http://hilfe.ovh.de/BridgeClient

I'm not able to ping the default gateway. What am i missing? I'm really new to this ESXi-thing, so please be kind.

VMware doesn't affect IPv6 routing. You should check with OVH if the provided addresses are correct. — Sander Steffann, Aug 19 '17 at 12:06
I double-checked the provided IPv6-adresses. In the OVH-Manager i can select an address out of this /64-stack: 2001:41d0:700:36d::/64, in my case i choosed ::2. — Tobias, Aug 19 '17 at 12:25
I expected as much :) IPv6 address parts consist of four characters. Therefore the fourth field is `036d`, and the first two characters are `03`. The default gateway should therefore be `2001:41d0:0700:03ff:ff:ff:ff:ff`. — Sander Steffann, Aug 20 '17 at 12:37
This is why you should always include real addresses in questions. Making bits with XXX might mask the actual problem :) — Sander Steffann, Aug 20 '17 at 12:39
Okay, in my next question i'll try to not make this mistake again. :-) — Tobias, Aug 22 '17 at 19:16

score 0 · Accepted Answer · edited May 15 '18 at 16:31

I finally found a solution for my problem. If you have the same problem like me, read these two guides carefully, especially this box:

The default Gateway for your IPv6 block (IPV6_GATEWAY) is always IP:v:6FF:FF:FF:FF:FF.

Some examples:
The IPv6 of the server is 2607:5300:60:62ac::/64.
The IPv6_GATEWAY will then be 2607:5300:60:62FF:FF:FF:FF:FF.

The IPv6 of the server is 2001:41D0:1:46e::/64.
The IPV6_GATEWAY will then be 2001:41D0:1:4FF:FF:FF:FF:FF.

Guide 1 (IPv4): https://docs.ovh.com/gb/en/dedicated/network-bridging/
Guide 2 (IPv6): https://docs.ovh.com/gb/en/dedicated/network-ipv6/

score 0 · Answer 2 · answered May 15 '18 at 15:52

0

IPv6: 2001:41d0:700:XXX:x
Netmask: 64
Gateway: 2001:41d0:700:XXff:ff:ff:ff:ff (as suggested by OVH)

Change your netmask to 56 and it will work. OVH guides are broken.

In case you wonder why changing the netmask setting to 56 fixes this, simply key in the IPv6 prefix you get from OVH into a IPv6 range calculator. Is 2001:41d0:700:XXff:ff:ff:ff:ff within the IPv6 range with /64? Now change to /56 and check the calculator again. You will see what I mean.

answered May 15 '18 at 15:52

Andryan Gouw

1

This will only sort-of work. But you will be unable to reach other OVH IPv6 addresses within the /56. Whether you _need_ to reach them is another question. – Michael Hampton May 15 '18 at 16:29

score 0 · Answer 3 · answered May 15 '18 at 16:36

The IPv6 gateway address that OVH uses is outside the /64 that is routed to your dedicated server. Therefore, you need to configure a static route to the gateway address.

On RHEL/CentOS and Fedora, you can configure static IPv6 routes with a /etc/sysconfig/network-scripts/route6-<interface> file. This file literally contains route additions that will be passed to ip route. For example:

From /etc/sysconfig/network-scripts/ifcfg-eno1 (only IPv6 configuration shown):

DEVICE="eno1"
NAME="eno1"
IPV6INIT="yes"
IPV6_FAILURE_FATAL="no"
IPV6_AUTOCONF="no"
IPV6ADDR="2607:5300:60:62ac::/64"

From /etc/sysconfig/network-scripts/route6-eno1:

2607:5300:60:62ac::/64 dev eno1
2607:5300:60:62ff:ff:ff:ff:ff dev eno1
default via 2607:5300:60:62ff:ff:ff:ff:ff dev eno1

During OS installation, if you simply configure the IPv6 address, prefix 64 and gateway address as given by OVH, the installer will create the necessary static routes for you.

Setup IPv6 on CentOS 7 in a ESXi-VM by OVH

3 Answers3