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migration script for router-advert sets link-mtu 0 on bridge interfaces
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Upgrading to latest rolling, the router-advert options got denested into service router-advert, but the bridge interface got set link-mtu 0, which caused it to fail to apply. Deleting link-mtu made it commit successfully.
Sadly no logs, I can't find any on disk from that failed commit.


Difficulty level
Unknown (require assessment)
Why the issue appeared?
Will be filled on close
Is it a breaking change?
Config syntax change (migratable)
Issue type
Bug (incorrect behavior)

Event Timeline

jjakob triaged this task as Unbreak Now! priority.Mar 25 2020, 5:18 PM
jjakob created this task.
jjakob created this object in space S1 VyOS Public.

Can you send me your previous config.boot file prior of the upgrade? I'm happy to take a look

c-po changed the task status from Open to In progress.Mar 25 2020, 7:01 PM
c-po claimed this task.

Actually I had link-mtu 0 on br0 for a long time now and it worked without problem previously, maybe 0 was a special meaning for radvd?
br0 is the only interface that had ipv6 router-advert, I included one of the eth's for completeness:

interfaces {
    bridge br0 {
        address 2001:db8::1/64
        aging 300
        description LAN
        firewall {
            local {
                name lan-local
        hello-time 2
        ipv6 {
            dup-addr-detect-transmits 2
            router-advert {
                cur-hop-limit 64
                link-mtu 0
                managed-flag true
                max-interval 600
                other-config-flag false
                prefix 2001:db8::/64 {
                    autonomous-flag true
                    on-link-flag true
                    valid-lifetime 2592000
                reachable-time 0
                retrans-timer 0
                send-advert true
        max-age 20
        member {
            interface eth0 {
            interface eth1 {
            interface eth2 {
            interface eth4 {
            interface wlan0 {
        priority 20480
    ethernet eth0 {
        duplex auto
        hw-id xx:xx:xx:xx:xx:xx
        smp-affinity auto
        speed auto

Good catch!

The problem was that I intended to delete the link-mtu node when its value was 0 "disabled" as configuringing a node that is disable makes no sense in my brain, when other values enable it. The node should be enabled when there's a valid configuration and if not specified it's disabled.

This was unfortunatley not handled by the migration script and the new validation catched it. Please re-upgrade from your previous vyos installation to one of the todays rolling releases. The bugfix will be included.

c-po changed Is it a breaking change? from Unspecified (possibly destroys the router) to Config syntax change (migratable).
erkin set Issue type to Bug (incorrect behavior).Aug 31 2021, 5:11 PM
erkin removed a subscriber: Active contributors.