Candra Setiawan Blog

Cisco mempunyai software register 16 bit yang ditulis pada nonvolatile memory. Configuration register diatur secara default untuk me-load Cisco IOS dari flash dan me-load startup-config dari NVRAM

Kita bisa mengubah configuration register untuk keperluan:

• Memaksa system untuk masuk bootstrap monitor
• Memilih sebuah boot source dan default boot filename
• Enable atau men-disable fungsi break
• Mengontrol alamat broadcast
• Mengatur baud rate terminal console
• Me-load software operating dari ROM
• Booting dari TFTP server

Konfigurasi default pada Cisco router adalah 0×2102

Nomor bit pada configuration register

Prefix 0x pada alamat configuration register (0×2102) untuk menunjukkan bilangan yang digunakan adalah hexadecimal

Maksud dari Nomor Bit

Bit ke 6 digunakan untuk mengabaikan isi dari NVRAM

Boot field

Untuk boot ke mode ROM Monitor atur configuration register ke 0×2100, kemudian reboot router. Pada router akan muncul rommon>

Untuk booting ke mini-IOS images pada ROM (dikenal sebagai RXBOOT), atur configuration register ke 0×2101. Maka akan tampil router(boot)> Jika ini jenis router lama, atau akan muncul rommon 1> jika router berbasiskan RISC terbaru dengan sebuah “smart ROM” pengganti dari mini IOS.

Nilai dari 0×2102 sampai 0×210F untuk memberi tahu pada router untuk menggunakan perintah boot yang spesifik di NVRAM. Semua nilai dalam bentuk hexadecimal, skemanya adalah 0-9 dan A-F. (A=10, B=11, C=12, D=13, E=14, dan F=15). Sehingga kita mengatur configuration register sampai 210(15), atau 1111 dalam bentuk binary.

MENGUBAH CONFIGURATION REGISTER

Sebelum mengubah configuration register, maka perlu mengetahui nilai configuration register yang sudah ada. Pada router ketikkan perintah:

Router>enable

Router#show version

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

System returned to ROM by power-on

System image file is “flash:c1841-advipservicesk9-mz.124-15.T1.bin”

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2102

Untuk mengubah configuration register

Router#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)#config-register 0×2101

Router(config)#^Z

%SYS-5-CONFIG_I: Configured from console by console

Router#show version

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

System returned to ROM by power-on

System image file is “flash:c1841-advipservicesk9-mz.124-15.T1.bin”

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0×2102 (will be 0×2101 at next reload)

PASSWORD RECOVERY

Bit ke 6 pada configuration register merupakan bit yang digunakan untuk memberi tahu router apakah harus menggunakan isi dari NVRAM, atau malah sebaliknya untuk mengabaikan isi dari NVRAM.

Nilai default dari configuration register adalah 0×2102, dimana bit ke tersebut dinyatakan off, jika nilai ini off maka router akan mencari dan me-loading konfigurasi yang disimpan pada NVRAM (startup-config). Untuk melakukan recovery password, kita perlu memberi nilai pada bit ke 6 tersebut, sehingga router akan mengabaikan startup-config yang terdapat pada NVRAM, sedangkan konfigurasi mengenai password tersendiri disimpan pada startup-config tersebut, jika startup-config diabaikan maka router tidak akan membaca password yang sudah ada.

Untuk melakukan recovery password pada router, hubungkan router pada program hyperterminal. Setelah itu matikanlah router, kemudian pada keyboard computer tekan Control+break, dan nyalakan lagi router. Router akan masuk ke ROM monitor, pada ROM monitor ketik perintah confreg 0×2142

rommon 1 > confreg 0×2142

rommon 2 > reset

Setelah direset maka router akan masuk ke configuration dialog, ketik no

System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Self decompressing the image :

########################################################################## [OK]

Restricted Rights Legend

Use, duplication, or disclosure by the Government is

subject to restrictions as set forth in subparagraph

(c) of the Commercial Computer Software - Restricted

Rights clause at FAR sec. 52.227-19 and subparagraph

(c) (1) (ii) of the Rights in Technical Data and Computer

Software clause at DFARS sec. 252.227-7013.

cisco Systems, Inc.

170 West Tasman Drive

San Jose, California 95134-1706

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

Image text-base: 0×60080608, data-base: 0×6270CD50

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

— System Configuration Dialog —

Continue with configuration dialog? [yes/no]:

Masuk ke privileges mode

Router>enable

Kemudian masuk ke Global Configuration Mode

Router#configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Berikan password yang baru

Router(config)#enable secret candra

Kembalikan konfigurasi kenilai default

Router(config)#config-register 0×2102

Router(config)#^Z

%SYS-5-CONFIG_I: Configured from console by console

Simpan ke startup config

Router#copy run startup-config

Destination filename [startup-config]?

Building configuration…

[OK]

Reload router

Router#reload

Proceed with reload? [confirm]

%SYS-5-RELOAD: Reload requested by console. Reload Reason: Reload Command.

System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Self decompressing the image :

########################################################################## [OK]

Restricted Rights Legend

Use, duplication, or disclosure by the Government is

subject to restrictions as set forth in subparagraph

(c) of the Commercial Computer Software - Restricted

Rights clause at FAR sec. 52.227-19 and subparagraph

(c) (1) (ii) of the Rights in Technical Data and Computer

Software clause at DFARS sec. 252.227-7013.

cisco Systems, Inc.

170 West Tasman Drive

San Jose, California 95134-1706

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

Image text-base: 0×60080608, data-base: 0×6270CD50

This product contains cryptographic features and is subject to United

States and local country laws governing import, export, transfer and

use. Delivery of Cisco cryptographic products does not imply

third-party authority to import, export, distribute or use encryption.

Importers, exporters, distributors and users are responsible for

compliance with U.S. and local country laws. By using this product you

agree to comply with applicable laws and regulations. If you are unable

to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

http://www.cisco.com/wwl/export/crypto/tool/stqrg.html

If you require further assistance please contact us by sending email to

export@cisco.com.

Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.

Processor board ID FTX0947Z18E

M860 processor: part number 0, mask 49

2 FastEthernet/IEEE 802.3 interface(s)

191K bytes of NVRAM.

31360K bytes of ATA CompactFlash (Read/Write)

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1, RELEASE SOFTWARE (fc2)

Technical Support: http://www.cisco.com/techsupport

Copyright (c) 1986-2007 by Cisco Systems, Inc.

Compiled Wed 18-Jul-07 04:52 by pt_team

%LINK-5-CHANGED: Interface Vlan1, changed state to up

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up

%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to administratively down

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down

%LINK-5-CHANGED: Interface Vlan1, changed state to administratively down

Press RETURN to get started!

Ketik enable dan masukkan password baru yang kita buat tadi

Router>enable

Password:

Router#

Jika interface pada router sudah ada konfigurasi mengenai IP address dan lain-lain, jangan lupa untuk masuk ke Interface mode karena seluruh interface kembali berada dalam kondisi down.