lagg Interfaces - don't do Gratuitous ARP?

[Steven Hartland]

On 22/09/2016 02:12, Ryan Stone wrote:
>
>
> On Wed, Sep 21, 2016 at 7:57 PM, Gleb Smirnoff <glebius at freebsd.org 
> <mailto:glebius at freebsd.org>> wrote:
>
>     IMHO, the original patch was absolutely evil hack touching multiple
>     layers, for the sake of a very special problem.
>
>     I think, that in order to kick forwarding table on switches, lagg
>     should:
>
>     - allocate an mbuf itself
>     - set its source hardware address to its own
>     - set destination hardware to broadcast
>     - put some payload in there, to make packet of valid size. Why
>     should it be
>       gratuitous ARP? A machine can be running IPv6 only, or may even
>     use whatever
>       higher level protocol, e.g. PPPoE. We shouldn't involve IP into
>     this Layer 2
>       problem at all.
>     - Finally, send the prepared mbuf down the lagg member(s).
>
>     And please don't hack half of the network stack to achieve that :)
>
>
> The original report in this thread is about a system where it takes 
> almost 15 minutes for the network to start working again after a 
> failover.  That does not sound to me like a switch problem.  That 
> sounds to me like the ARP cache on the remote system.  To fix such a 
> case we have to touch L3.
15mins is a long time however we don't do ARP correctly in this case, 
which is almost certainly the cause.