1
00:00:01,200 --> 00:00:07,260
So the poor field lost to value determines how the writer will boot

2
00:00:10,010 --> 00:00:19,610
that consists of four binary bits which are either set on or off a value of 0 means Romanova to a value

3
00:00:19,610 --> 00:00:22,930
of 1 means boot into our boot.

4
00:00:23,120 --> 00:00:28,760
In the old days all today means boot using the first operating system in Flash.

5
00:00:30,060 --> 00:00:37,240
Setting it to two or a great number such as F or e.

6
00:00:37,410 --> 00:00:44,070
In other words anything from 2 to F means normal boot.

7
00:00:44,140 --> 00:00:50,050
So this value is set to 2 or greater means normal boot.

8
00:00:50,060 --> 00:00:55,700
So in other words enables default booting from flash memory you can override that by using the boot

9
00:00:55,700 --> 00:00:59,360
system commands in the running config of a router.

10
00:00:59,770 --> 00:01:04,790
So on a radio you could use the boot system command to specify that a different operating system is

11
00:01:04,790 --> 00:01:06,220
used as an example.

12
00:01:06,410 --> 00:01:11,480
So the router would boot from a TFT server as an example.

13
00:01:11,480 --> 00:01:20,430
So in other words on the router you could use a command such as pooched system and tell the router to

14
00:01:20,430 --> 00:01:29,100
boot its operating system off a TFT piece of war and peace over as an example rather than puting the

15
00:01:29,100 --> 00:01:38,220
operating system from flash when I wrote it boots up it goes through a series of steps which include

16
00:01:38,280 --> 00:01:45,030
loading the Cisco Iowa software from Flash or if specified from somewhere else such as a nifty piece

17
00:01:45,030 --> 00:01:47,620
of into the ram of the router.

18
00:01:47,970 --> 00:01:56,160
The router will also load the configuration stored in startup config and apply that and use it as the

19
00:01:56,160 --> 00:01:57,750
running config.

20
00:01:57,750 --> 00:02:03,480
So here are the steps that it takes when booting up the first thing it does is perform the power on

21
00:02:03,480 --> 00:02:05,610
self test or post.

22
00:02:05,610 --> 00:02:11,280
This is a series of hardware tests that verify that all the components of a Cisco Rodolf functional

23
00:02:11,940 --> 00:02:12,620
during the test.

24
00:02:12,620 --> 00:02:15,340
The rod also determines which hardware is present.

25
00:02:15,580 --> 00:02:21,060
This executes from microcode that is stored in the system from.

26
00:02:21,180 --> 00:02:28,980
So he has a router and his APC are going to do an immediate reboot on the router

27
00:02:37,870 --> 00:02:44,540
so you can see the rod is booting up and then is loading the operating system.

28
00:02:44,590 --> 00:02:49,110
Now its going to do a power on self-test but thats not very clear on this router.

29
00:02:49,420 --> 00:02:57,490
So what Im going to do is show you the power on self tests on a Cisco switch so I'll do a reboot on

30
00:02:57,490 --> 00:02:58,520
the Cisco switch.

31
00:03:07,220 --> 00:03:15,640
And you can see the 29 50 bootloader is being used.

32
00:03:15,690 --> 00:03:21,570
It's now loading the operating system from flash.

33
00:03:21,690 --> 00:03:28,470
And what I'd like to show you here is notice the power on self tests that are shown on the switch so

34
00:03:28,470 --> 00:03:36,120
you can see clearly back power on self tests have been passed on the switch.

35
00:03:36,350 --> 00:03:40,520
And then the switch boots up and the interfaces come up.

36
00:03:40,520 --> 00:03:47,550
So scrolling back noticed power on self-test power on self-test can see the operating system is loaded

37
00:03:47,970 --> 00:03:50,830
and then the switches ready to start.

38
00:03:50,830 --> 00:03:55,420
Now something similar is taking place on a router.

39
00:03:55,570 --> 00:03:58,040
We just don't see it as clearly in the output.

40
00:04:02,240 --> 00:04:03,250
But here's the output.

41
00:04:03,260 --> 00:04:09,610
When I reloaded the router you can see run monitors initialized the program loads are taking place.

42
00:04:09,800 --> 00:04:14,460
The operating system is being decompressed and loaded.

43
00:04:14,590 --> 00:04:19,650
So the first step on a router is to perform a power on self-test.

44
00:04:19,900 --> 00:04:25,450
The router then loads and runs the bootstrap code which is used to perform subsequent events such as

45
00:04:25,450 --> 00:04:32,710
locating the Cecka Iowa software loading it into RAM and running it off to the Cisco Iowas software

46
00:04:32,740 --> 00:04:40,030
is loaded and running the bootstrap code is not used until the next time the rod he's reloaded will

47
00:04:40,030 --> 00:04:45,640
power cycled on this 1041 router.

48
00:04:45,870 --> 00:04:53,320
We can see that the bootstrap code is loading the operating system.

49
00:04:53,550 --> 00:04:57,660
And here we can see which version of operating system has been loaded into RAM.