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When a rocket boots up it's so just for Siska iris image in a specific sequence.

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It will search for the Cisco IOS based on what's configured in the configuration register whether there's

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a Iowas in Flash.

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If a TFT server is available or it will use run monitor.

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So when the router boots up the first thing it checks is the configuration register boot field.

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If the boot field is set to zero in hexadecimal it will load run monitor remember the configuration

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registers 16 binary bytes.

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By default it would be 0 x 2 1 0 to the last hexadecimal value specifies the boot field.

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So if that's set to 0 it will go into run monitor mode if it's set to a greater.

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In other words two three four five six seven eight and so forth up to f it will check for Buddh commands

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and load the Cisco Iowa image as specified in the boot command if no boot command is being configured

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it will boot an image in Flash.

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And typically it will boot the first Iowas image found in Flash.

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Unless you specify a boot command telling it to boot off a different operating system if no files are

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available in flash it will look for an Iowa image on a TV B server so it'll try and load a Cisco iris

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image from A to B server but if none is available then it will load Romont after the Strada.

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It has multiple files in flash so it has this operating system and this operating system in Flash.

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Notice the difference in the name.

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The one that was loaded is the one with underscore two in the name that was loaded from flash.

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The reason why that operating system was loaded is the configuration register set to the default.

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So the boot field is set to two but in the running configuration there is a boot command telling the

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router to boot from that second operating system.

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So the two files in flash this one and this one put the router was configured to boot off the second

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image has the full show run command.

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Notice she has the command in the running config telling the Rodda which image to boot from.

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So show version shows that image was loaded by the router on this router.

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However there are no boot commands.

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So show run pipe.

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Include boot doesn't show any boot commands specifying that the Rodda should boot from some other operating

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system.

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Short version shows which operating system was loaded and we can see that the configuration registers

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using the default value.

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So the router loaded the first operating system that it found in Flash.

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In other words the operating system.

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So you can specify with boot commands which operating system should be loaded by the router but by default

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it will simply use the first operating system found in Flash.

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Unless you override that with the boot system command.

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You could as an example specify that it boot from a TFT server or server as an example.

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So how do Cisco routers load highway configuration files when the operating system is loaded and started

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the rot it needs to be configured with IP addresses and other valleys to make it of any use.

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So it will typically look for the startup config in NV RAM.

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If there's no startup config and nv ram it will either begin or to install or enter the setup utility.

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So when the router boots up it looks for a startup config and nv ram.

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If it exists it will load that startup config.

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If there's no startup config it looks for an active link to another router and then tries to load a

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configuration from a TFT server using a protocol called slop.

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If that doesn't work it will prompt for the initial configuration dialog.