In this article I would show basic router configuration commands. These commands are the essential part of router configuration. For demonstration purpose I used packet tracer software. If you haven’t install packet tracer read our previous article to download and install packet tracer. Create a topology as given in following image
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.
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.
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
Use this command to view the status of the current layer 3 routed protocols running on your router
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
*1:46:13.169 UTC Mon Nov 1 2009
Will show you Router clock
will display a cached list of hosts and all of their interfaces IP addresses
Will show a list of all users who are connected to the router
will give you detailed information about each interface
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 22.214.171.124 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 126.96.36.199/8 is directly connected, Serial0/0/0 D 188.8.131.52/8 [90/40514560] via 184.108.40.206, 00:02:55, Serial0/0/0 D 220.127.116.11/8 [90/41026560] via 18.104.22.168, 00:02:54, Serial0/0/0 D 22.214.171.124/8 [90/41029120] via 126.96.36.199, 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: 10.0.0.0 188.8.131.52 Routing Information Sources: Gateway Distance Last Update 184.108.40.206 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
You are now in User mode. Type ? to view all the available commands at this prompt.
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 --More--
I have uploaded a configured and tested topology in case you are unable to locate the problem spot then download this configuration file. And try to find out where have you committed mistake
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