[j-nsp] Solved: MX: Hardware-Down for an irb logical unit

Chuck Anderson cra at WPI.EDU
Tue Apr 28 20:24:49 EDT 2015

On Wed, Apr 29, 2015 at 12:21:11AM +0000, Ben Dale wrote:
> Hi Chuck,
> On 29 Apr 2015, at 9:32 am, Chuck Anderson <cra at WPI.EDU> wrote:
> > What would cause an irb logical interface unit to stay in
> > "Hardware-Down"?  I'm using identical configs on 4 different routers
> > (different IPs of course), and one of them won't come up.  There is at
> > least one physical interface in the BD that is up.  The irb physical
> > interface is up.  There are many other irb logical units that are up
> > and working fine, just this one unit that is down.
> > 
> This is usually caused because there are no physical interfaces up in the bridge-domain.  
> I notice you've got an aggregated-ethernet interface in there - if you have LACP enabled, but no LACP partner, the physical link will stay up, but the logical interface will go down, thus taking down your IRB as well.

I've solved the problem.  There is No LACP, but there is STP.  The
problem was that MSTP was blocking the only link the VLAN was
configured on.  I had to move the VLAN to the correct MSTI.  Once
there was an interface in the BD that was up and not MSTP-blocked, the
irb unit came up.


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