Confreg 2142 Password Recovery and Config Wipeout

HOW TO force into ROM MON mode:

Press Break on the terminal keyboard within 60 seconds of power up in order to put the router into ROMMON.

An alternate break sequence is to setup the Hyperterminal session on a wrong baud rate, say 1200. About 10 to 15 seconds after power up, keep pressing the space bar (for about 10 seconds till you feel silly doing that). Close the Hyperterminal and reconnect at the correct baud rate of 9600 and you should see the ROMMON prompt.

If the break sequence does not work, refer to Standard Break Key Sequence Combinations During Password Recovery for other key combinations.


You're in ROMMON and you're really messed up. You can't even do tftpdnld because you don't have a tftp server nor a proper IOS config file. It's bad!

I think I even tried the password recovery mode, which would erase the running config file and all that.
ROMMON 1> confreg 2142
ROMMON 2> reset
The router should boot up in the skeleton configuration with no startup or no running, factory defaults to build up from scratch.

Well that didnt' seem to work so I swapped flash cards with another unit (don't know why I had to do that) but I was desparate and it worked. Now what will happen to the unit with the wrong flash?? Whatever.

So the recovered unit is now in the state of - revert to password recovery mode. You will lose the original configuration. The router will have no login, enable password nor telnet

do show version
Most important remember to change the confreg to 0x2102 (otherwise it will go back to 2142)
reload

The factory default setting for the configuration register is 0x2102. This indicates that the router should attempt to load a Cisco IOS  Software image from Flash memory and load the startup configuration with a console speed of 9600 baud. For most purposes, the factory default setting of the configuration register is the most appropriate. To change the configuration register to this setting, issue the configuration-register 0x2102 command, as shown:

Router(config)#config-register 0x2102

Circuit Switched Networks

Here are some quick facts lifted from a CCNA online quiz

Three accurate descriptions of Circuit Switched Networks
* With circuit switching a dedicated physical circuit is established, maintained and terminated through a carrier network for each communication session
* Circuit switching allows multiple sites to connect to the switched network of a carrier and communicate with each other
* ISDN is a circuit switched network

Three statements for PSTN
* Other than a modem, no additional equipment is required
* Relatively lost cost associated with the implementation of a PSTN connection link
* The maintenance of a public telephone network is very high quality with a few instances in which lines are not available

Three statements describe PPP
* A point to point (or serial) comms link provides a single preestablished WAN communications path from the customer premises through the carrier network ie telephone company to a remote network
* Carriers lease point to point lines usually, so they're often called leased lines
* For a point to point line, the carrier dedicates fixed transport capacity and facility hardware to the line of a customer

Three statements describe WAN bandwidth
* North American standard to describe bandwidth in DS numbers (DS0, DS1...) that refers to the rate and format of the signal
* Bandwidth on a serial connection can be incrementally increased to accommodate the need for faster transmission
* Bandwidth refers to the rate at which data is transferred over the comms link

HDLC
* Includes support for both PPP and multipoint configurations
* Cisco HDLC there is no windowing or flow control
* HDLC specifies an encapsulation method for data on synchronous serial data links using frame character and checksum

Function of PPP
* twist: Authentication phase of PPP session is not necessarily required
* PPP originally emerged as an encapsulation protocol for transporting IP traffic over PPP links
* PPP provides router to router and host to network connections over synchronous and asynchronous circuits
* The LCP in PPP is used for establishment, configuration and testing the data-link connection

Considerations for PPP
* PPP links require minimal expertise to install and maintain
* usually offer a high quality of service
* provide permanent dedicated capacity that is always available

Cisco ICND1 Flashcard: A Brief History of the Internet

The US DOD researchers figured out a way to break up messages into smaller parts, and sending each part to the destination, whereupon reassembly of the original message would be possible. This is called the packet system.

In 1972, ARPANET developers created the first email message software for the purpose of communicating and coordinating projects

In 1984, DNS was introduced to give the world domain endings like .edu, .com, .gov, .org and other country codes.

A 3-way handshake
send-SYN
SYN-ACK
TCP ACK

HVAC and Power Rating Calculators

A quick link to find a Dell Energy Star rating calculator for heat generation and cooling requirements for Dell models for 48U, 42U or 24U Poweredge racks.

I was actually looking for the rating for one machine but it makes sense the application is making the calculations based on an entire rack.  Launch the page for Dell Star Online here.

Another important factor to consider is how many units you can fit into the rack given the power available to the rack. Here is a useful answer for Dell Poweredge Server Power Requirements rated for PE 2950 as a starting point.

Check again for more information about Water Cooled Racks or High Performance Cooling solutions.
Whitepaper for Watts and Volt-Amps