If the configuration register value on a Cisco router has been set to
0x2102, and the router is unable to load a valid IOS image from Flash, the
router will:
1. Attempt a net boot using the boot field value in the configuration
register to determine the filename to use when requesting the IOS image to
be downloaded.
NOTE: If there is a boot system command stored in the startup-config file,
a net boot will NOT be attempted.
2. If a valid IOS image cannot be found, the router attempts to boot from
the RXBOOT file in ROM.
3. If this file cannot be found, the router continues to boot from ROM
Monitor. An IOS can be sent to the router via Xmodem through the console or
AUX port if an AUX port exists.
Configuration registers and boot sequences seemed to be one of those poorly
explained and understood areas - so recently as part of a project I've been
working on, I spent a bit of time researching how exactly these processes
work. When I first removed my IOS images from Flash, I didn't get the net
boot attempt--like as Adam and Raul described. However, once I removed my
boot system command from the startup-config file, I received the message:
%Error opening tftp://255.255.255.255/cisco2-C1600 (Timed out)boot of
"cisco2-C1600"
So it does work as explained by the Network Academy book... Hope that
helps!
- Leigh Anne
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of
A.Strobel
Sent: November 6, 2000 3:44 PM
To: [EMAIL PROTECTED]
Subject: Boot Sequence
How in the world is it possible that there are so many contradicting answers
to a simple question:
On a router: config register is 0x2102
there is no boot system command in the configuration
and there is no valid image file in the flash
what will happen?
Simple question, right?
Now watch the answers:
http://www.cisco.com/univercd/cc/td/doc/product/access/acs_fix/cis2500/2501/
2500ug/conf.htm
- xtocid288623
This link says:
If after five attempts a valid Cisco IOS image is not found in Flash memory,
the router reverts to boot ROM mode.
So, the answer is [boot ROM]
Next: Cisco Net Academy, Sem.2 CBT Chapter 5, 5.1.2 or Cisco Networking
Academy Program: First Year Companion Guide, pg. 252. says:
- Try to boot from network and then from ROM
So, the answer is [Network, ROM]
Next: CCNA exam book by Wendell Odom (official cisco book)
says: will not proceed and terminate the boot process. You must do password
recovery to change the cofig register.
Can someone with a hard evidence ( apparently my evidences suck ) please
tell
me which answer is the correct one?
No guesses please.
TIA,
A. Strobel
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