1721 IOS Dropping to ROMMON

Unanswered Question
Aug 13th, 2008

Hi All,

I have a weird one. I have a 1721 loaded with a very recent IOS image. FA0 is pointing to the internet and is configured for DHCP. My WIC-4ESW is on the private LAN. The LAN has a four port 3Com gigabit consumer switch. My PC and my router are plugged into the 3Com. The router boots fine and is ready for connections. But it drops straight to ROMMON the moment I turn on OR off my PC. I then have to reboot the router for it to be okay. The motherboard of the PC is a D875PBZ. Suggestions?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
spremkumar Wed, 08/13/2008 - 22:20


Did u you check you out for any error in logs ??? also if its getting restarted then check out for the reload reason using show version command ...


smothuku Thu, 08/14/2008 - 01:24

Hi ,

Can you send us the "show Tech" output of the router.



vaisharm Thu, 08/14/2008 - 01:59


Is your router connected to the PC using a console cable aswell? Please provide 'show version' output from the router after it reboots and comes back up.


Gccadministrator Thu, 08/14/2008 - 18:09

Hi All,

Sorry it took so long to get back to you. That whole "work" thing gets in the way of the "life" thing. Anyway, I think I have figured it out. I have another computer to use for logging collection. I moved the console cable to it and turned on the Intel box. The router did not drop to ROMMON. So it looks like there is some kind of a power surge or COM command sent out at turn on and turn off that throws the 1721 to ROMMON. I tried to use syslog to capture what was happening but the router did not provide any more information. It just left IOS and went to ROMMON. I also used CONT command in ROMMON and the router went back to IOS. So I think it's just a strange thing between the 1721 console cable and the Intel board's COM port.

vaisharm Sun, 08/17/2008 - 22:02


Looks like your configuration register is set to 0x2002. You can verify this by looking at the last line in show version output. Ox2002 means enable break sequence.

When your PC boots up it sends a break sequence to the router causing it to drop into ROMMON. If it is 0x2002, then change it to 0x2102 which would ignore the break signal.


Router#conf t

Router(config)#config-register 0x2102


You can issue show version at this point which would show the config register value would be set to 0x2102 on next reload.


Confirm the config register value again. Connect your old PC back and check if the problem still persits.




This Discussion