[GLLUG] radvd and vlans

Tim Woodall t at woodall.me.uk
Tue Feb 6 19:22:41 UTC 2018

On Sun, 4 Feb 2018, Tim Woodall via GLLUG wrote:

> Hi all,
> I'm getting some very bizarre behaviour from radvd when I try to add
> vlan interfaces.
> The possibly unusual feature is that the eth0 vlans share a common
> subnet with eth0. Most people have one subnet per vlan.
> Radvd is sitting there ticking nicely advertising on eth0. radvdump also
> shows I've got some announcements coming in on eth2 but they don't have
> any useful information in them and I'm not using eth2 for IP (and can
> disable ipv6 on the interface)
> I bring up the two vlans: ifup eth0.100; ifup eth0.102
> And suddenly my RA that were going out on eth0 are going out on eth2
> instead! Adding RA stanzas for eth0.100 and eth0.102 and they all go out
> on eth2!

This seems to have been a bug in the version of radvd I was using. It
wasn't just related to vlans, even adding a new stanza for another
interface was enough to cause everything to go wrong. No idea quite what
it was as the bugs I could find reported appear to be related to adding
an interface - but I was restarting radvd.

I've upgraded the server and now the RAs appear to be on the correct
interfaces. Haven't yet had time to try out the vlan stuff again.


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