Thursday, January 3, 2013

Configuring HDLC

High-level Data Link Control - Basic Configuration

There are three steps:
1. Assign an IP address to the interface

ip address ---

2. Assign the encapsulation protocol

encapsulation hdlc
and then execute

no shutdown

3. Run the bandwidth command

bandwidth ----(speed)

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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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Routers - Basics 1

Differences between Routers and Switches:
1. IP configurations is different
2. Setup questions are different
3. Routers have an AUX port, which Switches dont

Router Interfaces:
1. Ethernet
2. Serial

Important commands:

show interface ---- shows everything, all interfaces and their properties

show ip interface brief ---- brief status of all interfaces

R2#show ip interface brief
Interface                  IP-Address      OK? Method Status                Prot                ocol
FastEthernet0/0        1.1.3.1           YES NVRAM  up                    down               
Serial0/0                  1.1.1.2            YES NVRAM  up                    up                 
FastEthernet0/1       unassigned      YES NVRAM  up                    up                 
Serial0/1                  unassigned      YES NVRAM  down              down               
Loopback0              192.168.1.2     YES NVRAM  up                    up
 
     

Interface Status:
There are two status' for any interface -

1. Line
2. Protocol

These can only be UP or DOWN. There are 4 combinations for these 2 status' to be in:
1. Administratively down, down ---- means the interface is in shutdown mode
2. down, down ---- means the interface is DOWN physically even when it is in no shutdown mode
3. up, down ---- means the interface is ok physically (line is up) but there's a problem at data-link (protocol) level
4. up, up ---- no problems :) router is up and running


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