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Recovering an EX4500 with Virtual Chassis module that is stuck in db prompt after downgrading from 11.1 to 10.4 or lower release.

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Article ID: KB21116 KB Last Updated: 25 May 2011Version: 1.0
Summary:
The Virtual Chassis (VC) module for the EX4500 Switch is supported starting with Junos OS 11.1 and later releases.  If you downgrade, with the VC module installed, to 10.4R4 or earlier Junos OS software release the install will fail and the switch will get stuck at the debug (db) prompt. This article explains how to recover an EX4500 stuck in this state.



Symptoms:
The intraconnect module on the EX4500 is supported from 10.3 onwards and is required on EX4500s running 10.4 and later releases for full functionality. The EX4500 Virtual Chassis module is only supported in 11.1, and later releases, with the introduction of EX4500 virtual chassis mode.

Attempts to install 10.4R4, or earlier Junos OS software, on an EX4500 switch with a Virtual Chassis module installed will cause the switch to get stuck in debug mode at the db prompt with the following error:

*********************************************************************************************************************************************************
KDB: enter:
******No Intraconnect Module or Virtual Chassis Module Found******

Please do the following:
1. Disconnect power from the switch.
2. Remove the faulty module, if any.
3. Insert a working module.
4. Reconnect power to the switch.

dog: ERROR - reset of uninitialized watchdog
[thread pid 0 tid 0 ]
Stopped at kdb_enter+0x1a4: addis r3, r0, -0x7fb2
db>

*********************************************************************************************************************************************************

The switch cannot be recovered from the loader prompt and installation of any software version from the loader prompt will fail with the same error:


*********************************************************************************************************************************************************
loader> install --format file:///jinstall-ex-4500-10.4R3-domestic-signed.tgz


Package /jinstall-ex-4500-10.4R3-domestic-signed.tgz is signed...


/kernel data=0x5542c8+0x55da0 syms=[0x4+0x54ac0+0x4+0x7c60b]


Kernel entry at 0x800000e0 ...


GDB: no debug ports present
KDB: debugger backends: ddb
KDB: current backend: ddb
dog: ERROR - reset of uninitialized watchdog
KDB: enter:
******No Intraconnect Module or Virtual Chassis Module Found******
Please do the following:
1. Disconnect power from the switch.
2. Remove the faulty module, if any.
3. Insert a working module.
4. Reconnect power to the switch.

dog: ERROR - reset of uninitialized watchdog
[thread pid 0 tid 0 ]
Stopped at kdb_enter+0x1a4: addis r3, r0, -0x7fb2
db>

*********************************************************************************************************************************************************
Solution:
To recover an EX4500 switch stuck in this condition, please follow these steps:

1. Replace the Virtual Chassis module with an Intraconnect module.
  •             Procedure to remove the Virtual Chassis module  (See Link Below)
  •             Procedure to install the Intraconnect module          (See Link Below)

2. Boot the switch and interrupt boot process at the loader prompt.


3. At the loader prompt, install the Junos OS 11.1R2, or later, software package for EX4500 using a tftp server or usb device:

loader>install tftp://10.3.217.100/k jinstall-ex-4500-11.1R1.10-domestic-signed.tgz

(See Link Below - Troubleshooting Software Installation.  Section "Recovering fomr a Failed Software Upgrade on an EX Series Switch)
4. After the software installation is completed, replace the Intraconnect module with the Virtual Chassis module.

NOTE: The EX4500 Virtual Chassis module is only supported starting with Junos OS 11.1 and all later releases.

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