[SOLVED] Cloned CentOS8 VMWare VM has duplice IPv6 Link Local Address

Issues related to configuring your network
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otakugenx
Posts: 2
Joined: 2020/05/19 15:04:54

[SOLVED] Cloned CentOS8 VMWare VM has duplice IPv6 Link Local Address

Post by otakugenx » 2020/05/19 15:12:54

We are a VMWare house with mostly CentOS and Red Hat machines. I usually create a "base" machine, configure out all the basics and then when I need a new machine I clone it. Upon cloning it gets a new MAC address. I usually delete the clones network interface and create a whole new one also. But, after cloning and adding a new interface and deleting the old interface I have 2 IPv6 link-locals being generated and 1 of them conflicts with the “parent” machine. I have tried deleting the conflicting link-local but on reboot it comes back. Since the auto generated ipv6 link-locals are not set in the config I can not simply remove them there. How can I get rid of the conflicting link-local? Is this something to worry about?
Last edited by otakugenx on 2020/05/19 16:04:30, edited 1 time in total.

otakugenx
Posts: 2
Joined: 2020/05/19 15:04:54

Re: Cloned CentOS8 VMWare VM has duplice IPv6 Link Local Address

Post by otakugenx » 2020/05/19 16:02:47

OK I figured it out. RHEL and CentOS 8 generate their link-locals based on the Machine-ID. That is not based on the MAC address and is not regenerated on cloning. The Link-Local address should be disabled by duplicate address detection, but you can fix the error so it does not happen at all. You need to regenerate a new Machine-ID. Make the machine-id file (/etc/machine-id) writable. Copy it to a backup file then delete the contents of it. Run systemd-machine-id-setup again. Change the permissions on the machine-id file back to original, 444.

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