Same problem, same routers, all afternoon digging around and finally solution reached until modifying cookie in ROMMON . First of all; let me say that when you modify this file your smartnet may not be useful anymore. So, if you have smartnet open a case to TAC and wait them to arrange an interactive session for you.
How I solve the issue is;
- Boot the router in ROMMON
- Go to priv mode (you need priv password; write "cookie" and copy&paste first line to the following web site http://ers.pp.ru/cgi-bin/priv.cgi - In priv mode modify cookie file by using "cookie" command again. This may be very trick since every offset is represented in hex . That's why you need to dig more; you will see "FF"s on the corrupted part of this file (I am not talking about continous FF s at the end of the file).
-Change them base on the reference below: (I also used another running 2801's cookie for some true references)
bytes 0x00-0x07: 04 ff c3 06 00 1e be b5 - MAC address (FA0/0,F0/1) you can change if you > want bytes 0x08-0x0F: 84 38 43 00 22 c1 8b 46 > bytes 0x10-0x17: 4f 43 31 31 34 39 32 37 - PCB Serial Number ( you MUST assign your PCB > serial number from motherboard.
I can confirm myself that a corrupt cookie on one of my ISR routers produced an identical issue - a router simply hanging during boot, unable to proceed. A corrupt cookie was found as the cause.
What I can recommend at this stage for everyone is to use the command show diag in IOS and cookie in ROMMON to display and back up the cookie values from their routers, and in case of cookie corruption, to have its original value using which it can be restored.
By the way, it is close to raising suspicions: why do these cookie values get corrupted so often? Every now and then, some router becomes a brick after the cookie value goes havoc. The thing is, if the cookie format was documented (there's nothing so special in it), it would be possible to repair the router in the field instead of RMAing etc.
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