Apr 11, 2009

Configuration Register instructions

The Configuration Register is a 16 bit field that is converted into a hexadecimal value for convenience.  As you know each hexadecimal character represents 4 bits.  Hexadecimal numbers go from 0 to F and represent decimal numbers from 0 to 15.  Hexadecimal numbers generally are preceded by a 0x to clue us in on the fact that we are looking at a hexadecimal number.  By default a Cisco router has a Configuration Register setting of 0×0101 so the actual 16 bits would look like 0000000100000001 so now you see that finally there is a use for the hexadecimal numbering system!  The bits in the Configuration Register are numbered 0 to 15 and you start from the far right:

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

So for every 4 bits we translate that into hex, observe the following typical Configuration Register:

2

1

0

2

0

0

1

0

0

0

0

1

0

0

0

0

0

0

1

0

Each bit position serves a function with the exception of bits 4, 5 and 9 which were used in the early days when Cisco routers used a gas engine, but are not currently used.  Here is what each bit position is used for:

0

Boot Field

Set to ON by default

1

Boot Field

2

Boot Field

 

3

Boot Field

 

4

Headlight Relay

No longer used

5

Horn Relay

No longer used

6

Ignore NVRAM

Very cool

7

OEM

No practical function

8

Ignore Console Break

Set to ON by default

9

Starter Solenoid

No longer used

10

IP Broadcast

Works with bit 14

11

Console Connection Speed

 

12

Console Connection Speed

 

13

Boot to flash if Netboot fails

Not a bad idea

14

IP Broadcast

Works with bit 10

15

Ignore NVRAM

Diagnostic messages

The fields in gray you can ignore, the fields in green are that you will typically be interested in.  The boot field if set to 0 will boot into ROMMON mode and not load any IOS.  If the boot field is set to 1 then the first IOS image found in flash will be loaded.  If the boot field is set from 2 to F then the router loads the system image specified by boot system commands in the startup configuration file. When the startup configuration file does not contain boot system commands, the router tries to load a default system image stored on a network server.

If the number 6 bit is switched on, the router will not load the configuration file stored in NVRAM and will load IOS without any configuration.  This is a how you do password recovery, you boot up the router and hit the break key, this will dump you into ROMMON mode, from here you use the confreg utility to alter the Configuration Register so that when you boot the machine it doesn’t pull the config from NVRAM, then you can edit the password in the config, then don’t forget to change the Configuration-Register while you are in IOS so that when you reload it will load the contents of NVRAM and you’re in like Flint! 

The Configuration Register can be set in ROMMON or in IOS.  In IOS the command is: config-register 0×2101 of course substitute the value you want.  If the third hex digit from the left is 4 that means skip whatever’s in NVRAM.  Bits 11 and 12 set the console connection speed, 9600 is as fast as it will go and you get that speed by leaving those bits set to 0.  Bits 10 and 14 control if IP broadcasts are sent using all zeros or all ones, leave these bits set to 0, the factory default.  Bit 8 controls the break key, leave it set ON this way if your router has been up for 30 days and you accidentally send a break to the router, it won’t suddenly drop everything and go into ROMMON mode.  The router will always respond to a break key sent right away when booting up.  Although you will never need to dick around with the bits 8,10,11 and 12 pay attention to your Config Register because even though you know better, your workmates will change these values every couple of days for reasons unknown.  Check the value of your Configuration Register by using the show version command.

Apr 9, 2009

遠傳籲正視不合理網際網路互連費用

更新日期:2009/04/09 18:51

(中央社記者葉代芝台北9日電)台固與中華電信互連費引發爭議,遠傳電信今天也呼籲,為維護台灣網路用戶利益及網路上下游產業健全發展,社會應正視電信業者長期遭收取不合理的網際網路互連費用。

台灣大哥大子公司台灣固網與遠傳電信子公司速博2家ISP(網際網路服務業者)今天罕見地召開聯合記者會。遠東集團電信事業群家用服務事業處副總經理鄭智衡質疑,中華電信長期持有固網市場資源,並一再濫用其市場地位,在網際網路巿場遲遲未及充分競爭下,消費者權益誰來維護?

鄭智衡指出,3家民營固網業者,無論再怎麼努力,也無法對抗巿場獨大!目前所有民營固網業者的網際網路市佔率仍不到25%,而中華電信卻要求單一業者的IP Address(網路位置)數量須達1/3以上才能對等互連,這是同業互連費用談判的 6大條件中,民營固網業者唯一無法做到的。

鄭智衡質疑,在資源傾斜的情形下,民營業者的IPAddress要到何年何月才能達到1/3以上的市佔率?何時才能對等談話,共同提昇產業發展?

另外,鄭智衡指出,ADSL電路是全民共同擁有的資產,理當由全民共享,電路費用不應該由特定的業者制價,應透過共同自由市場機制,以消費者需求為依歸來制訂合理的電路服務費用。

鄭智衡指出,民營固網業者的成本不斷攀高,讓民營固網業者命在旦夕,基於爭取網路頻寬以及支付合理費用,以及為台灣電信產業健全發展的立場,速博 (遠東集團電信事業群)以同理心表達期望政府相關單位正視此次事件,並能有一個公平共同協商的機會。