#22 How to configure router

Hello friends, today I would show basic router configuration commands. These commands are the essential part of router configuration. 


Router#show running-config

Building configuration...

Current configuration : 419 bytes
!
version 12.4
no service password-encryption
!
hostname Router
!
ip ssh version 1
!
interface FastEthernet0/0
[output is Omitted] 


Active configuration is known as running-configuration. You can view it from router command line interface. show running-config command will display active configuration from memory. You can run this command from privileged mode. On a Cisco router active configuration is not saved automatically. So it would lost automatically in the event of power failure. To avoid it you need to save it manually with copy command.


Router#show flash

System flash directory:
File  Length   Name/status
  1   33591768 c1841-advipservicesk9-mz.124-15.T1.bin
[33591768 bytes used, 30424616 available, 64016384 total]
63488K bytes of processor board System flash (Read/Write)

Flash memory is a special kind of memory on the router that contains the operating system image file(s). Unlike regular router memory, Flash memory continues to maintain the file image even after power is lost.


Router#show history

The routers Command Line Interface (CLI) maintains by default the last 10 commands you have entered in memory .

You can retrieve previous commands by pressing UP Arrow Key

You can retrieve next commands by pressing Down Arrow Key



Router#show protocols

Use this command to view the status of the current layer 3 routed protocols running on your router


Router#show version

Cisco IOS Software, 1841 Software (C1841-ADVIPSERVICESK9-M), Version 12.4(15)T1,
RELEASE SOFTWARE (fc2)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2007 by Cisco Systems, Inc.
Compiled Wed 18-Jul-07 04:52 by pt_team

ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

System returned to ROM by power-on
System image file is "flash:c1841-advipservicesk9-mz.124-15.T1.bin"
[output is Omitted]
Cisco 1841 (revision 5.0) with 114688K/16384K bytes of memory.
Processor board ID FTX0947Z18E
M860 processor: part number 0, mask 49
2 FastEthernet/IEEE 802.3 interface(s)
1 Low-speed serial(sync/async) network interface(s)
191K bytes of NVRAM.
31360K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0x2102 

This command will give you critical information, such as: router platform type, operating system revision, operating system last boot time and file location, amount of memory, number of interfaces, and configuration register.


Router#show clock

*1:46:13.169 UTC Mon Nov 1 2009

Will show you Router clock


Router#show hosts

will display a cached list of hosts and all of their interfaces IP addresses


Router#show users

Will show a list of all users who are connected to the router


Router#show interfaces

will give you detailed information about each interface


Router#show protocols

will show the global and interface-specific status of any layer 3 protocols


Router#show ip interface brief

Interface          IP-Address     OK? Method Status                Protocol

FastEthernet0/0     10.0.0.1        YES manual up                     up

FastEthernet0/1    unassigned      YES manual administratively down  down

Serial0/0/0         20.0.0.1        YES manual up                     up

Vlan1               unassigned      YES manual administratively down  down
Router# 

This command will show brief descriptions about interface. This command 
mostly used in troubleshooting. There may be three possible conditions 
of status. 

UP :- interface is up and operational 
DOWN :- physical link is detected but there are some problem in configurations. 
Administratively down :- port is disable by shutdown command (Default mode of any port on router.) 

R1#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
       i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
       * - candidate default, U - per-user static route, o - ODR
       P - periodic downloaded static route

Gateway of last resort is not set

C    10.0.0.0/8 is directly connected, FastEthernet0/0
C    20.0.0.0/8 is directly connected, Serial0/0/0
D    30.0.0.0/8 [90/40514560] via 20.0.0.2, 00:02:55, Serial0/0/0
D    40.0.0.0/8 [90/41026560] via 20.0.0.2, 00:02:54, Serial0/0/0
D    50.0.0.0/8 [90/41029120] via 20.0.0.2, 00:02:50, Serial0/0/0

R1#

This command will give a detail about known route. Router will not 
forward packet if route is not shown here for that packet. Router’s 
routing decision is made by this routing table.

R1#show controllers serial 0/0/0
Interface Serial0/0/0
Hardware is PowerQUICC MPC860
DCE V.35, clock rate 64000
idb at 0x81081AC4, driver data structure at 0x81084AC0 

Most common use of this command is to find out whether the port is DCE 
end or DTE. If the port is DCE end then clock rate and bandwidth command
will require. As you can see in output that port is DCE.

R1#show ip protocols

Routing Protocol is "eigrp  1 "
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Default networks accepted from incoming updates
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  EIGRP maximum hopcount 100
  EIGRP maximum metric variance 1
Redistributing: eigrp 1
  Automatic network summarization is in effect
  Automatic address summarization:
  Maximum path: 4
  Routing for Networks:
     10.0.0.0
     20.0.0.0
  Routing Information Sources:
    Gateway         Distance      Last Update
    20.0.0.2        90            16
  Distance: internal 90 external 170
 

Use this command to know about running routing protocols. This will give the complete status about routing protocols likes on which interface its receiving updates and on which interface its broadcasting update what is time intervals
press enter to get back router prompt Router>
You are now in User mode. Type ? to view all the available commands at this prompt. Router>?
From privilege mode you can enter in configuration mode by typing configure terminal you can exit configuration mode type exit or <CTL>+z

Router>enable
Router#config terminal
Router(config)#exit
Router# 

To view all commands available from this mode type: ? 
and press: enter This will give you the list of all available commands 
for the router in your current mode. You can also use the question mark 
after you have started typing a command. For example if you want to use a
 show command but you do not remember which one it uses 'show ?' will 
output all commands that you can use with the show command.

Router#show ? 
access-expression List access expression
access-lists List access lists
backup Backup status
cdp CDP information
clock Display the system clock
cls DLC user information
compress Show compression statistics
configuration Contents of Non-Volatile memory