[j-nsp] MX, ARP cache with L2 bridging

[Chuck Anderson]

On Tue, Sep 18, 2012 at 07:35:28PM +0200, Nicolaj Kamensek wrote:
> Hi list,
> 
> I've just learned that even if the MX operate in L2 bridging mode
> with irb interfaces and an IP address moves from one bridged
> interface to another, the arp cache timeout still applies. This is a
> pain since this might affect convergence time in case of a link
> failure when spanning-tree chooses an alternate path and the ip is
> then seen on xe-0/0/1 instead of xe-0/0/0. Is there anything I can
> do to optimize that behaviour? Clearing the arp cache every few
> minutes is obviously not a good idea in respect of the cpu load.

That is not true in my experience.  L2 MAC Learning takes effect
immediately upon seeing traffic enter the new MX port.  The ARP entry
will point to the new L2 next-hop immediately.