Switching

Hi everybody,

https://www.juniper.net/us/en/products-services/switching/ex-series/datasheets/1000511.page

Features and Benefits

EX4600 Ethernet switches include the following key features and benefits:

• Unified in-service software upgrade (unified ISSU): With its Intel core processor, the EX4600 switch allows Junos OS to run within a virtual machine (VM) on Linux. Junos OS runs in two separate VMs in active and standby pairs; during software upgrade cycles, the switches seamlessly move to the newer software version while maintaining intact data plane traffic. This true topology-independent ISSU (TISSU), an industry-first software upgrade feature for a fixed-configuration top-of-rack switch, is supported across all L2 and L3 protocols and doesn’t need the support of any other switches to perform an image upgrade.

I am looking for some details:

1) How ISSU works on EX4600 with these VMS

2) If active VM gets corrupted ( abrupt power outage), how EX4600 recovers? does it boot up using standby VM?

3) do these VMS run the same JUNOS OS when we upgrade JUNOS on EX4600 using  normal " request software add" ( not using ISSU)?

Thanks and have a good night!!

Hi sarahr202,

Looking at your query I remember my team and I had this conversation a long ago, see here a brief answer to your questions:  

1) How ISSU works on EX4600 with these VMS
All communications between the running VMs takes place through the host bridge, which is a virtual switch and part of the Linux-based hypervisor.
When TISSU is initiated, a second VM (VM-B in our example) is launched with the new version of the software. Once VM-B has launched, it synchronizes protocol states with VM-A. When that synchronization process is complete, VM-B seamlessly takes over switch operations and VM-A shuts down.

To support the TISSU operations, a number of connections and communications between the two VMs must exist. The connections, as shown on the slide, are either active or passive. The solid lines represent active connections while the dotted lines are passive connections. The passive connections become active when the graceful Routing Engine switchover (GRES) event associated with TISSU is complete.

2) If active VM gets corrupted ( abrupt power outage), how EX4600 recovers? does it boot up using standby VM?
A recovery image is created automatically on the switches. If a previously-running switch is powered on and unable to boot using a Junos OS image, you can boot the switch using the recovery Junos OS image by selecting one of the saved images.

Because the architecture of EX4600 is identical with the one of QFX5100, the same process applies to EX4600.
https://kb.juniper.net/InfoCenter/index?page=content&id=KB34866&cat=EX_SERIES&actp=LIST&showDraft=false

3) do these VMS run the same JUNOS OS when we upgrade JUNOS on EX4600 using normal " request software add" ( not using ISSU)?
The primary VM, which is used to implement and manage any third-party or Juniper VMs, runs Junos OS. The standby Junos OS VM is used when a topology-independent in-service software upgrade (TISSU) is performed.
Meaning, during normal operation only one, the Master RE will operate. 

If this clears out all question please mark as resolved so we call help others!  

Thanks, 

esmontes,