[j-nsp] EX4200 L2 to MX960 L3

[Chuck Anderson]

On Thu, Feb 26, 2015 at 09:14:03AM -0500, adfjklaufao akjvlauroe wrote:
> Hello
> 
> We connect our devices to a 4200 and run layer 2 to an AE on the 960. The
> layer 3 is on the ae on the 960. Currently the layer 3 stays up when
> the physical layer port is down on the 4200.  Is there a way to have the
> layer 3 shutdown when the physical port on the 4200 is down?

Is the port on the MX960 also down when the port on the EX4200 is
down?  Are you using auto-negotiation on the link?  If you don't use
autonegotiation, and there is a single fiber fault (one direction
only) then the MX could see the physical link as up even when the EX
sees the physical link as down.  The fix is to use auto-negotiation if
the devices are directly connected.  If there is another device
in-between, like a service provider cloud, active optics, media
converter, etc., then you may have to use LACP, Ethernet OAM, or BFD
for L3 protocols.  Those solutions also work in the directly-connected
case.

Is there a bridge-domain w/irb interfaces on the MX associated with
the ae interface?  In my experience, if you have the layer 3 config
directly on the physical interface or on the ae, with no bridge-domain
or irb involved, then the layer 3 DOES shutdown when the physical port
shuts down.  BUT if you have an irb interface where the layer 3 config
is, then it will stay up if there are any other interfaces in the same
bridge-domain that are still up.