Cisco Support Community
Community Member

Problem with 2851 - looks like power off but is not

I got problem with my router 2851 for last 3 days. Suddenly it hangs up - looks like there is no power - but it is switched on, no errors, just looks like powered off.

It happens not everyday.

When I switch off power button and ON - router starts to work normally. Is it problem with Power Adapter?

(of course I changed cable, checked power socket and plug etc...)

here are some details about my router

Cisco IOS Software, 2800 Software (C2800NM-IPVOICE-M), Version 12.4(7a), RELEASE SOFTWARE (fc3)

Cisco 2851 (revision 53.51) with 249856K/12288K bytes of memory.
2 Gigabit Ethernet interfaces
96 Serial interfaces
4 Channelized T1/PRI ports
DRAM configuration is 64 bits wide with parity enabled.
239K bytes of non-volatile configuration memory.
62720K bytes of ATA CompactFlash (Read/Write)

I use it as VoIP gateway with ISDN lines.

Anyone has similar experience?

Cisco Employee

Re: Problem with 2851 - looks like power off but is not

Hi Marek,

If the box is hanging (I.E. it does not reply anymore to the

console, or does not forward traffic, and the only way to recover

is to power cycle the box), then I would need you to follow

this action plan:

1) When the console is not responding:

   - Verify that the power supply is on.

   - Verify the router LED status. If all LEDs are down, it is most likely

     an issue with the power supply of the router.

2) If traffic still flows through the router.

    If it does, you may have a problem of low resources (cpu, mem, etc.) and that may be caused by the traffic:

   - Disconnect network interfaces and see if the router responds

   If it does verify cpu, memory and interfaces configurations. You may want to contact Cisco Support at this stage to help troubleshooting this.

3) If Traffic Does Not Pass Through:

   1- change the config-register to enable the break key

         Router(config)#config-register 0x2002

   2- reload the router to use the new config register

   3- Send the break sequence when the problem occurs from the console. The ROM Monitor

      prompt ">" or "rommon 1 >" must be displayed

      Try this before the hang to ensure the procedure you follow is correct. Use the "c" (continue) command to get out of rommon.

      ---> When a hang occurs, if you can't go to rommon but managed to go before a hang, you probably have a defective hardware

   4- If you can go to rommon during a hang, You probably face an IOS bug and should consider an upgrade.

      If you can't, you'll need help from Cisco Support. Capture a stack trace. For this, collect the output from either the "k

      50" or "stack 50" commands.

   5- Issue the c or cont command to continue.

   6- Repeat the three last steps several times to ensure that multiple

      points in a continuous loop have been captured.

   7- After you have obtained several stack traces, reboot the router to

      recover from the hung state

   8- Open a new service request with Cisco Support to decode the stack trace and help troubleshooting the hang.

Hope this helps!

Community Member

Re: Problem with 2851 - looks like power off but is not

Thanks Raphael for very detailed steps.

When the router is down is totally down. No traffic, no response, no console. Like without power.

When the hung occurs - I can not do anything - no rommon.

Probably power supply is dead...but..if I wait about 2-3 min and turn on - router boot up again.

Sometimes I swich on - and nothing going no power. So again turn off and on - and starts.

So 90% its power there any way to diagnose it?

thanks in advance

Cisco Employee

Re: Problem with 2851 - looks like power off but is not

Hi Marek,

I'm afraid you should have a hardware issue then. There is no real way to troubleshoot this than trial and error with other hardware. If you have a support contract with hardware replacement I guess it's time to replace the router. If you have support contract, you should see a link upper right of this thread to open a new service request and all the informations will be transferred to the case.

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