2501 Router keeps rebooting

[trevorh13]

Hi guys,

Have just bought a secondhand 2501 router. On bootup it tells me that a dialer must be specified, continues to boot. It gets as far as trying to bring the ports up (it cant as they are not connected) including a dialer0. It then reports that it was configured from memory before rebooting itself. I suspect that the Startup-config is maybe corrupted and so have tried to boot into boot rom mode so I configure the config register to ignore thet Startup file - however the router will not respond to a control-break sequence. Any ideas on how I can physically force the router to boot into rom mode? I have never come across this problem before and am unsure what to do next!

Regards

Trevor Hopkins

CCNA, MCSE

 

[Cluebird]

Are you issuing the correct break sequence for the terminal program? Each terminal uses a different combination.

If you're unable to get into ROMMON through a break sequence, someone may have entered the command "no service password-recovery" in which case the password recovery mechanism doesn't work. That usually means ship the box to Cisco.

However, another thing you may try is to remove the Flash chip from the box and reboot it. When the router can't locate an IOS it'll eventually end up in RXboot or ROMMON. From either of these places you can then set the config-register to ignore the NVRAM.

HTH

 

[trevorh13]

Yep is definately correct control+break sequence. Have tried removing the NVRAM but unsuprisingly made no difference. On the 2501 the IOS is stored on the rom chips and if I remove that I am guessing the router will npot be able to boot into rommon either is that correct?

Sounding like it is going to be a return to cisco isnt it!

 

[Cluebird]

On the 2501, the IOS is not stored on the ROM chips. What is stored on the ROM are: POST instructions, Bootstrap code, RXBoot image, ROMMON instructions. Some ROM chips do not have the RXBoot image.

However, you should have a slot0 for a Flash SIMM and another slot for the DRAM. Here's a link that shows the architecture:

http://www.optimumdata.com/shop/files/cisco/2500/2500_Series_Replacing_The_Boot_ROMs.pdf

If you remove the Flash SIMM and boot the router, it should end up at a prompt that looks like Router(boot)> for the RX Boot or > for rommon. Either prompt will let you change the configuration register. The router will cycle a couple times trying to find a full IOS but will eventually get to what looks like the setup dialog which you can bypass to get to the CLI.

Regards,
Tad

 

[Cluebird]

Another link that may help with the break sequence:

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a0080174a34.shtml#topic3

Tad

 

[Cluebird]

Another thought: I had a router that behaved like this when it didn't have enough RAM to load the configuration. Once the router was running, I could load the configuration and all worked well until I needed to reload. I was able to use the break sequence on that box, though. For your issue, if the configuration is too large for the DRAM, make sure you have a full 16 MB on the router (which is the maximum for the platform).

Regards,
Tad

 

[trevorh13]

Removed the Flash simm and did indeed go to a > prompt. Erased the startup-conf and it booted a treat after so problem fixed.

Rather concerned that the hadout I received on the 2501 infrastructure when on my Cisco CCNa course defines the Flash stick as NVRAM and have thought it as such since!

Many thanks for your assistance.

Regards

Trevor

 

[Cluebird]

Documentation errors are always frustrating but I've never seen any technical book that is 100% correct. I always review course materials for errors but I don't always find everything either. Being human does have limits.

I tell my learners as they flail with router configurations the only reason I am an instructor is becuase I've screwed up more than they have! Those miskates give experience which is vital to being credible since we all learn best by making mistakes. We are all learners in this business.