Wireguard, allowed-ips, ipv6 and multicast

Roman Mamedov rm at romanrm.net
Tue May 19 11:22:40 CEST 2020

On Tue, 19 May 2020 11:09:24 +0200
nicolas prochazka <prochazka.nicolas at gmail.com> wrote:

> Hello,
> I'm trying to use vxlan encapsulated into Wireguard tunnel, with a
> multicast group for announcement.
> Ex :
> ip -6 link add vxlan100 type vxlan id 100 dstport 4789  local
> `wg0Ip6_lock`  group ff05::100 dev wg0 ttl 5
> All works very well when i set wg tunnel with ::/0  as allowed-ips,
> but if i'm trying to be more restrictive, as ff05::/32  for example,
> it does not work.
> Is a specific interaction between allowed-ips and multicast group in ipv6 ?

AFAIK multicast or broadcast do not work over WG at all. There's no special
handling for it, and no mechanism to duplicate the same packet and send it out
to several peers at once.

For VXLAN you have to rely on adding each peer's MAC and its underlying IP
explicitly via "bridge fdb append". To make it simpler you could use MACs and
IP(v6)s generated from peers' public keys, so there will be no need for any
centralized system of tracking and management for those. Or as I do, just
generate them from hashes of peers' human readable names.

With respect,

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