[j-nsp] EX4200 Virtual chassis ??

[Tore Anderson]

* Rachid DHOU

> We have two EX4200 switches, mainly used for L2 functionalities.
> We want to add two new EX4200 Switches and we want to connect them with the
> old switches.
> 
> i have two possibilities :
> 
> * Either, interconnect them and control everything with STP.
> * or use Virtual chassis.
> 
> 
> Please advise, what is the best way ? did you try Virtual chassis in EX ?
> Do you have other options ?

We have several VCs from both EX4200s and EX4500s (no mixed VCs though),
and disregarding some troubles with the former when the EX product line
was brand spanking new several years ago, they've been rock solid and I
wouldn't hesitate to recommend it over a traditional approach with STP.
You'll get one management interface, and you can build a loop-free
redundant network without STP wasting your bandwidth on blocked ports.

The core switch in one of our data centres is a two-node EX4500 VC with
LAGs to each downstream switch/device and upstream routers. The LAGs has
at least one member from each physical node in the VC, so it's all fully
redundant and I'm very happy with the setup.

The largest downside with it is that upgrading JUNOS, you will have a
30-60 sec downtime on the LACP and OSPF adjacencies, due to the fact
that a VC will not form if the member nodes have different JUNOS
versions. So after first having upgraded the line-card node, when
rebooting the routing-engine node, the upgraded line-card must start
everything from scratch when assuming the routing-engine role. This is
about to improve though, as I hear JUNOS 12.1 has gained support for
NSSU. Haven't tried it myself though, so I don't know if it's mature
enough to be trusted quite yet. (Interested in hearing about any
experiences though.)

BTW: Make sure to enable no-split-detection in your VC, or your two
EX4200s will be mutually dependent and you'll have no HA.

Best regards,
-- 
Tore Anderson
Redpill Linpro AS - http://www.redpill-linpro.com