NSSU was introduced for the EX8200 series Switches starting with 10.4, and later releases.

Nonstop software upgrade (NSSU) enables you to upgrade the software running on a Juniper Networks EX8200 Ethernet Switch with redundant Routing Engines or on an EX8200 Virtual Chassis with redundant XRE200 External Routing Engines using a single command and with minimal disruption to network traffic.

Requirements for NSSU:

1. GRES (Graceful Routing-Engine switchover) should be enabled
   

   {MASTER.EN_US}[edit]
root#show chassis
    redundancy {
        graceful-switchover;
    }

If GRES is not enabled, use the following command to enable it:
{MASTER.EN_US}[edit]
root# set chassis redundancy graceful-switchover

• NSR (Nonstop Active Routing) should be enabled

{MASTER.EN_US}[edit]
root# run show task replication
Stateful Replication: Enabled
RE mode: Master

Protocol Synchronization Status
PIM Complete

If NSR is not enabled, use the following command to enable it:
{MASTER.EN_US}[edit]
root# set routing-options nonstop-routing

• Chassis should have dual REs and both should be operational (should not see "present" on any slot in 'show chassis routing-engine' output)

{MASTER.EN_US}[edit]
root# run show chassis routing-engine
Routing Engine status:
Slot 0:
Current state Master
Election priority Master (default)
Temperature 26 degrees C / 78 degrees F
DRAM 2048 MB
Memory utilization 18 percent
CPU utilization:
User 0 percent
Background 0 percent
Kernel 4 percent
Interrupt 1 percent
Idle 95 percent
Model RE-EX8208
Serial ID BT0909120542
Start time 2011-02-10 08:50:41 UTC
Uptime 15 hours, 48 minutes, 28 seconds
Last reboot reason Router rebooted after a normal shutdown.
Load averages: 1 minute 5 minute 15 minute
0.06 0.04 0.05
Routing Engine status:
Slot 1:
Current state Backup
Election priority Backup (default)
Temperature 26 degrees C / 78 degrees F
DRAM 2048 MB
Memory utilization 14 percent
CPU utilization:
User 0 percent
Background 0 percent
Kernel 0 percent
Interrupt 1 percent
Idle 99 percent
Model RE-EX8208
Serial ID BT0909120542
Start time 2011-02-10 19:31:06 UTC
Uptime 5 hours, 7 minutes, 53 seconds
Last reboot reason 0x1:power cycle/failure


• Both the REs should run same Junos version

{MASTER.EN_US}[edit]
root# run show version invoke-on all-routing-engines
re0:
--------------------------------------------------------------------------
Model: ex8208
JUNOS Base OS boot [10.4R1.9]
JUNOS Base OS Software Suite [10.4R1.9]
JUNOS Kernel Software Suite [10.4R1.9]
JUNOS Crypto Software Suite [10.4R1.9]
JUNOS Online Documentation [10.4R1.9]
JUNOS Enterprise Software Suite [10.4R1.9]
LC JUNOS Installation Software [10.4R1.9]
JUNOS Routing Software Suite [10.4R1.9]
JUNOS Web Management [10.4R1.9]

re1:
--------------------------------------------------------------------------
Model: ex8208
JUNOS Base OS boot [10.4R1.9]
JUNOS Base OS Software Suite [10.4R1.9]
JUNOS Kernel Software Suite [10.4R1.9]
JUNOS Crypto Software Suite [10.4R1.9]
JUNOS Online Documentation [10.4R1.9]
JUNOS Enterprise Software Suite [10.4R1.9]
LC JUNOS Installation Software [10.4R1.9]
JUNOS Routing Software Suite [10.4R1.9]
JUNOS Web Management [10.4R1.9]
Below config is NSSU config part needs to be added to the config:

{MASTER.EN_US}[edit]
root# show chassis
nssu {
     upgrade-group Bala {
         fpcs [ 0 2 4 ];
     }
     upgrade-group Mridhu {
         fpcs [ 1 3 ];
     }
}
redundancy { 
     graceful-switchover;
}

Perform NSSU:

{MASTER.EN_US}[edit]
root# run request system software nonstop-upgrade reboot /var/tmp/jinstall-ex-8200-11.1-20110207.0-domestic-signed.tgz
Chassis ISSU Check Done
ISSU: Validating Image
ISSU: Preparing Backup RE
Pushing bundle to re1
WARNING: A reboot is required to install the software
WARNING: Use the 'request system reboot' command immediately
Backup upgrade done
Rebooting Backup RE

Rebooting re1
ISSU: Backup RE Prepare Done
Waiting for Backup RE reboot
GRES operational
Initiating Chassis In-Service-Upgrade
Chassis ISSU Started
ISSU: Preparing Daemons
ISSU: Daemons Ready for ISSU
ISSU: Starting Upgrade for FRUs
ISSU: Preparing for Switchover
ISSU: Ready for Switchover
Checking In-Service-Upgrade status
Item Status Reason
FPC 0 Online
FPC 1 Online
FPC 2 Online
FPC 3 Online
FPC 4 Online
Resolving mastership...
Complete. The other routing engine becomes the master.
ISSU: RE switchover Done
ISSU: Upgrading Old Master RE
WARNING: A reboot is required to install the software
WARNING: Use the 'request system reboot' command immediately
ISSU: Old Master Upgrade Done
ISSU: IDLE

For more information, refer to XXX in the technical documentation.

Verify versions:

root@:RE:1% cli sh version invoke-on all
re0:
--------------------------------------------------------------------------
Model: ex8208
JUNOS Base OS boot [11.1-20110207.0]
JUNOS Base OS Software Suite [11.1-20110207.0]
JUNOS Kernel Software Suite [11.1-20110207.0]
JUNOS Crypto Software Suite [11.1-20110207.0]
JUNOS Online Documentation [11.1-20110207.0]
JUNOS Enterprise Software Suite [11.1-20110207.0]
LC JUNOS Installation Software [11.1-20110207.0]
JUNOS Routing Software Suite [11.1-20110207.0]
JUNOS Web Management [11.1-20110207.0]

re1:
--------------------------------------------------------------------------
Model: ex8208
JUNOS Base OS boot [11.1-20110207.0]
JUNOS Base OS Software Suite [11.1-20110207.0]
JUNOS Kernel Software Suite [11.1-20110207.0]
JUNOS Crypto Software Suite [11.1-20110207.0]
JUNOS Online Documentation [11.1-20110207.0]
JUNOS Enterprise Software Suite [11.1-20110207.0]
LC JUNOS Installation Software [11.1-20110207.0]
JUNOS Routing Software Suite [11.1-20110207.0]
JUNOS Web Management [11.1-20110207.0]
root@:RE:1% cli
{MASTER.EN_US}
root>

• Understanding Nonstop Software Upgrade on EX Series Switches
• Example: Configuring Nonstop Software Upgrade on EX Series Switches