Recovery EPROM Cookie on Router Cisco

Tagged: Cisco router

Sometimes when rains a lighting could damage your router, that’s what happened to me last week.The problem was that the lighting deleted the cookies of my router’s eprom, it contains the data that the bootloader use to determine the MAC address,the CPU version,the vendor etc. Based on this informations the IOS runs or not on the platform, if these cookie are lost (my chase) the router cannot start…..

The router will be in ROMMON status, so don’t try to use the TFTPDNLD command or XMODEM to load the IOS because it’s still in the Flash.
Here’s the steps to follow to repair the router:

1- in the rommon mode digit the command PRIV that allows to you to enter in the privileged mode, use the password 0000 (four zeros) and enter.

2- if you cookies are corrupt you’ll see this situation:
>>rommon 1 > cookie
>>WARNING: Cookie information is corrupt
>>
>>cookie:
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>>rommon 2 >

3- now type the command COOKIE so you can set the values manually.When you insert them you just need to insert the values after the :
Below you can see good cookies of a 827 router:

byte 0×00 – Version: 01
byte 0×01 – Vendor (Recommended Value: 0×01): 01
bytes 0×02-0×07 – Ethernet HW Address: 00 04 27 fe 00 ea
byte 0×08-0×08 – Processor (Recommended Value: 0×3e): 3e (0×3E for 827
e_machine=62)(0×5B for soho77 e_machine=91)
byte 0×09-0×09 – NVRAM Size (Recommended Values: 256K – 0×00): 00
byte 0×0a-0×0a – CPU Speed (Recommended Value: 50Mhz – 0×01): 01
byte 0×0b-0×0b – Unused: ff
bytes 0×0c-0×0d – On-board PM ID: 01 ff
bytes 0×0e-0×0f – MAC Address Allocated: 00 00
bytes 0×10-0×17: 00 00 00 00 00 00 00 00
bytes 0×18-0×22: 4a 41 44 05 42 30 39 ** ** 03 01 (Processor board ID
JAD054209**)+(CPU revision 0×301)
bytes 0×23-0×24 – Deviation: 6f e6 (hardware revision 6FE6)
bytes 0×25-0×2c: 00 00 00 00 ff ff ff 50 (50 should be cpu_type)
bytes 0×2d-0×2d – Board Config: 04
bytes 0×2e-0×31: 49 11 ec 03
bytes 0×32-0×37 – WAN MAC Address: ff ff ff ff ff ff
bytes 0×38-0×3f: ff ff ff ff ff ff ff ff
bytes 0×40-0×47: ff ff ff ff ff ff ff ff
bytes 0×48-0×4f: ff ff ff ff ff ff ff ff
bytes 0×50-0×57: ff ff ff ff ff ff ff ff
bytes 0×58-0×5f: ff ff ff ff ff ff ff ff
bytes 0×60-0×67: ff ff ff ff ff ff ff ff
bytes 0×68-0×6f: ff ff ff ff ff ff ff ff
bytes 0×70-0×77: ff ff ff ff ff ff ff ff
bytes 0×78-0×7f: ff ff ff ff ff ff ff ff

As i told you the important values are number after the : as you can see let’s see the first two rows of the previous example :

byte 0×00 – Version: 01 —–> insert only 01
byte 0×01 – Vendor (Recommended Value: 0×01): 01 —> insert 01
and the same for all the others rows.

The final situation of the cookies will be something like this:

01 01 00 b0 c2 8e 5e 81 5b 00 01 ff 01 ff 00 00
00 00 00 00 00 00 00 00 4a 41 44 05 31 30 50 38
33 04 01 00 00 00 00 00 00 ff ff ff 50 04 49 11
ec 04 ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff

(these are exact cookies for a soho77)

At the end you just need to reset your router and your IOS and configuration will be there ready to work again.

jotfco 2005

PS: sorry for my “not perfect” english.