Sometimes you’re going to come across a router you need to work on where someone’s changed the password and forgotten to write it down, and sometimes that person may or may not be you. Regardless of the reason, how to you get in to a router which you’re locked out of?
You’ll need a few bits of kit to get you started. First, a 1700 or 1800 router (obviously) which is unusable. Second, you’ll need a Cisco console cable (light blue with an RJ-45 on one end and a DB9 serial connector on the other). Finally you’ll need a computer with a serial port and a VT100 program of some description. Hyperterm will do in a pinch, but something like Zoc or PuTTY is my preference.
Configuration procedure:
- Turn the router off and connect with your serial cable. You’ll need to set your settings as 9600 baud, no parity, 8 data bits and 1 stop bit.
- When you see the rommon 1> prompt, enter confreg 2×0142 and press enter. This says you want to boot from flash, but don’t want to actually enable the stored config. This means that you’ll have access to the stored-config, but won’t have any passwords in the way.
- When you see the rommon 2> prompt, enter reset to reboot into the new configuration.
- During startup, enter no when asked any questions and you’ll be presented with the router> prompt.
- Type enable and press enter, and you’ll be at the router# prompt with full elevated privileges.
- Use configure memory to manually change the stored config to your liking, or use a TFTP server to load a new config on the router. You can also copy startup-config running-config to load the startup config into memory – if you do this and it locks you out again, just reboot and you’ll be back at the router> prompt.
- Whatever you do, don’t use copy running-config startup-config, or you’ll blow away your entire config and end up with a completely blank router and have to start from scratch.
- If you’ve copied your config to running, use enable secret desired_password to change your password.
- Issue no shutdown commands for any interface you intend to use, as using this procedure automatically sets everything to shutdown. If you’re loading a new config via TFTP, make sure that you include a no shutdown command on every interface.
- Once you’re happy with your config, change your startup register so that the unit starts properly next time it’s rebooted. Enter configuration terminal and use the command config-register 0x2102 and hit enter.
- Use write memory or copy running-config startup-config to commit all changes to flash. It’s probably a good idea to reboot and test your new config, ensuring that your passwords are correct and that all your interfaces are running with show ip interface brief. If it doesn’t work and you’re still locked out, rinse and repeat.
Configuration Example:
Router>enable Password: Password: Password: % Bad secrets Router>show version Cisco Internetwork Operating System Software IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 07-Dec-99 02:21 by phanguye Image text-base: 0x80008088, data-base: 0x80C524F8 ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1) Router uptime is 3 minutes System returned to ROM by abort at PC 0x802D0B60 System image file is "flash:c2600-is-mz.120-7.T" cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory. Processor board ID JAB031202NK (3878188963) M860 processor: part number 0, mask 49 Bridging software. X.25 software, Version 3.0.0. Basic Rate ISDN software, Version 1.1. 2 Ethernet/IEEE 802.3 interface(s) 2 Serial(sync/async) network interface(s) 1 ISDN Basic Rate interface(s) 32K bytes of non-volatile configuration memory. 8192K bytes of processor board System flash partition 1 (Read/Write) 8192K bytes of processor board System flash partition 2 (Read/Write) Configuration register is 0x2102 Router> !--- The router was just powercycled, and during bootup a !--- break sequence was sent to the router. ! *** System received an abort due to Break Key *** signal= 0x3, code= 0x500, context= 0x813ac158 PC = 0x802d0b60, Vector = 0x500, SP = 0x80006030 rommon 1 > confreg 0x2142 You must reset or power cycle for new config to take effect rommon 2 > reset System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1) Copyright (c) 1999 by cisco Systems, Inc. TAC:Home:SW:IOS:Specials for info C2600 platform with 32768 Kbytes of main memory program load complete, entry point: 0x80008000, size: 0x6fdb4c 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 Internetwork Operating System Software IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 07-Dec-99 02:21 by phanguye Image text-base: 0x80008088, data-base: 0x80C524F8 cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory. Processor board ID JAB031202NK (3878188963) M860 processor: part number 0, mask 49 Bridging software. X.25 software, Version 3.0.0. Basic Rate ISDN software, Version 1.1. 2 Ethernet/IEEE 802.3 interface(s) 2 Serial(sync/async) network interface(s) 1 ISDN Basic Rate interface(s) 32K bytes of non-volatile configuration memory. 8192K bytes of processor board System flash partition 1 (Read/Write) 8192K bytes of processor board System flash partition 2 (Read/Write) --- System Configuration Dialog --- Would you like to enter the initial configuration dialog? [yes/no]: no Press RETURN to get started! 00:00:19: %LINK-3-UPDOWN: Interface BRI0/0, changed state to up 00:00:19: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up 00:00:19: %LINK-3-UPDOWN: Interface Ethernet0/1, changed state to up 00:00:19: %LINK-3-UPDOWN: Interface Serial0/0, changed state to down 00:00:19: %LINK-3-UPDOWN: Interface Serial0/1, changed state to down 00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0, changed state to down 00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up Router> 00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1, changed state to up 00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, changed state to down 00:00:20: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/1, changed state to down 00:00:50: %SYS-5-RESTART: System restarted -- Cisco Internetwork Operating System Software IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 07-Dec-99 02:21 by phanguye 00:00:50: %LINK-5-CHANGED: Interface BRI0/0, changed state to administratively down 00:00:52: %LINK-5-CHANGED: Interface Ethernet0/0, changed state to administratively down 00:00:52: %LINK-5-CHANGED: Interface Serial0/0, changed state to administratively down 00:00:52: %LINK-5-CHANGED: Interface Ethernet0/1, changed state to administratively down 00:00:52: %LINK-5-CHANGED: Interface Serial0/1, changed state to administratively down 00:00:53: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to down 00:00:53: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/1, changed state to down Router> Router>enable Router#copy startup-config running-config Destination filename [running-config]? 1324 bytes copied in 2.35 secs (662 bytes/sec) Router# 00:01:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:1, changed state to down 00:01:24: %LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0/0:2, changed state to down Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#enable secret < password > Router(config)#^Z 00:01:54: %SYS-5-CONFIG_I: Configured from console by console Router#show ip interface brief Interface IP-Address OK? Method Status Protocol Ethernet0/0 10.200.40.37 YES TFTP administratively down down Serial0/0 unassigned YES TFTP administratively down down BRI0/0 193.251.121.157 YES unset administratively down down BRI0/0:1 unassigned YES unset administratively down down BRI0/0:2 unassigned YES unset administratively down down Ethernet0/1 unassigned YES TFTP administratively down down Serial0/1 unassigned YES TFTP administratively down down Loopback0 193.251.121.157 YES TFTP up up Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#interface Ethernet0/0 Router(config-if)#no shutdown Router(config-if)# 00:02:14: %LINK-3-UPDOWN: Interface Ethernet0/0, changed state to up 00:02:15: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet0/0, changed state to up Router(config-if)#interface BRI0/0 Router(config-if)#no shutdown Router(config-if)# 00:02:26: %LINK-3-UPDOWN: Interface BRI0/0:1, changed state to down 00:02:26: %LINK-3-UPDOWN: Interface BRI0/0:2, changed state to down 00:02:26: %LINK-3-UPDOWN: Interface BRI0/0, changed state to up 00:02:115964116991: %ISDN-6-LAYER2UP: Layer 2 for Interface BR0/0, TEI 68 changed to up Router(config-if)#^Z Router# 00:02:35: %SYS-5-CONFIG_I: Configured from console by console Router#copy running-config startup-config Destination filename [startup-config]? Building configuration... [OK] Router#show version Cisco Internetwork Operating System Software IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 07-Dec-99 02:21 by phanguye Image text-base: 0x80008088, data-base: 0x80C524F8 ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1) Router uptime is 3 minutes System returned to ROM by abort at PC 0x802D0B60 System image file is "flash:c2600-is-mz.120-7.T" cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory. Processor board ID JAB031202NK (3878188963) M860 processor: part number 0, mask 49 Bridging software. X.25 software, Version 3.0.0. Basic Rate ISDN software, Version 1.1. 2 Ethernet/IEEE 802.3 interface(s) 2 Serial(sync/async) network interface(s) 1 ISDN Basic Rate interface(s) 32K bytes of non-volatile configuration memory. 8192K bytes of processor board System flash partition 1 (Read/Write) 8192K bytes of processor board System flash partition 2 (Read/Write) Configuration register is 0x2142 Router#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Router(config)#config-register 0x2102 Router(config)#^Z 00:03:20: %SYS-5-CONFIG_I: Configured from console by console Router#show version Cisco Internetwork Operating System Software IOS (tm) C2600 Software (C2600-IS-M), Version 12.0(7)T, RELEASE SOFTWARE (fc2) Copyright (c) 1986-1999 by cisco Systems, Inc. Compiled Tue 07-Dec-99 02:21 by phanguye Image text-base: 0x80008088, data-base: 0x80C524F8 ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1) Router uptime is 3 minutes System returned to ROM by abort at PC 0x802D0B60 System image file is "flash:c2600-is-mz.120-7.T" cisco 2611 (MPC860) processor (revision 0x202) with 26624K/6144K bytes of memory. Processor board ID JAB031202NK (3878188963) M860 processor: part number 0, mask 49 Bridging software. X.25 software, Version 3.0.0. Basic Rate ISDN software, Version 1.1. 2 Ethernet/IEEE 802.3 interface(s) 2 Serial(sync/async) network interface(s) 1 ISDN Basic Rate interface(s) 32K bytes of non-volatile configuration memory. 8192K bytes of processor board System flash partition 1 (Read/Write) 8192K bytes of processor board System flash partition 2 (Read/Write) Configuration register is 0x2142 (will be 0x2102 at next reload) Router#
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