Link-local and ACLs

Theodore Baschak theodore at
Mon Jul 24 21:52:16 CEST 2017

On Mon, Jul 24, 2017 at 12:46 PM, David Farmer <farmer at> wrote:

> In practice Neighbor Discovery, and other critical protocols, need
> link-local addresses to talk to other link-local addresses and some
> multicast addresses.
> Also, in theory a link-local address could talk to a GUA or ULA address on
> the same link. However, in practices does this really happen? If it does
> happen in practice what are circumstances?
> Thanks
> --
> ===============================================
> David Farmer               Email:farmer at
> Networking & Telecommunication Services
> Office of Information Technology
> University of Minnesota
> 2218 University Ave SE        Phone: 612-626-0815 <(612)%20626-0815>
> Minneapolis, MN 55414-3029   Cell: 612-812-9952 <(612)%20812-9952>
> ===============================================

Not quite 100% related, but I had an upstream provider put an artisanal
handcrafted IPv6 BCP38 ACL that didn't allow link-locals to talk to the
multicast range (or to the GUA on-link address possibly) on a port, and it
caused problems after a reboot I believe only. Things were able to keep
working for quite a while if I recall.

Theodore Baschak - AS395089 - Hextet Systems - -
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