Routers - Basics 2

Assigning IP addresses to interfaces:
Each interface on a router needs to have an IP address in order to function.

ip address address mask ---- assigns the IP address and mask to the interface

Example:
Here's the current IP for Fa0/0 (after running the command: show ip interface brief)
R2# show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            10.1.1.1        YES manual up                    down

And here's the same info after running the command: ip address 10.1.1.4 255.255.255.0
(after going into the configuration mode for this particular interface)

R2# show ip interface brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            10.1.1.4        YES manual up                    down


Initial configuration of a Cisco router
setup is the command that gets you in the initial setup mode when issued from the enable-mode EXEC
At the end of the setup process, you are given 3 choices:
0 - go back to the CLI
1 - go back to setup mode
2 - keep the resulting config

Upgrading Cisco IOS:
1 - download the latest IOS image from cisco.com
2 - place the image on a TFTP server
3 - copy the image to flash memory on the router

copy tftp flash - is the command

IOS Boot Sequence:
There are 4 steps in the Boot Sequence:
1 - POST: Power On Self Test that the router performs
2 - the Bootstrap loader is copied from ROM to RAM
3 - Bootstrap decides which OS to load into RAM
4 - If the OS is IOS, it loads the config into RAM (running-config)

Configuration Register:
16-bit number
Controls settings for basic programs
Tells router what OS to load

Low-order 4 bits out of 16 form the boot field.
Boot field = 0 ---- load ROMMON
Boot field = 1 ---- load IOS
Boot field = 0 ---- try each command in the startup-config file, if nothing works, load IOS

show version command:

gives a lot of info but the main things it tells you are:
1. IOS version
2. uptime
3. RAM
4. NVRAM
5. Configuration register settings.

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