In preparation of your CCNA exam, we want to make sure we cover the various concepts that we could see on your Cisco CCNA exam. So to assist you, below we will discuss the CCNA concepts of Cisco Router Commands. As you progress through your CCNA exam studies, I am sure with repetition you will find this topic becomes easier. So even though it may be a difficult concept and confusing at first to learn all the Cisco commands, keep at it as no one said getting your Cisco certification would be easy!

  • Config# terminal editing – allows for enhanced editing commands
  • Config# terminal monitor – shows output on telnet session
  • Config# terminal ip netmask-format hexadecimal|bit-count|decimal – changes the format of subnet masks
  • Config# hostname ROUTER_NAME
  • Config# banner motd # TYPE MESSAGE HERE # – # can be substituted for any character, must start and finish the message
  • Config# description THIS IS THE SOUTH ROUTER – can be entered at the Config-if level
  • Config# clock timezone Central -6
    # clock set hh:mm:ss dd month yyyy
    – Example: clock set 14:35:00 25 August 2003
  • Config# config-register 0x2100 – ROM Monitor Mode
  • Config# config-register 0x2101 – ROM boot
  • Config# config-register 0x2102 – Boot from NVRAM
  • Config# boot system tftp FILENAME SERVER_IP – Example: boot system tftp 2600_ios.bin
  • Config# boot system ROM
  • Config# boot system flash – Then – Config# reload
  • Config# cdp run – Turns CDP on
  • Config# cdp holdtime 180 – Sets the time that a device remains. Default is 180
  • Config# cdp timer 30 – Sets the update timer.The default is 60
  • Config# int Ethernet 0
  • Config-if# cdp enable – Enables cdp on the interface
  • Config-if# no cdp enable – Disables CDP on the interface
  • Config# no cdp run – Turns CDP off
  • Config# ip host ROUTER_NAME INT_Address – Example: ip host lab-a
  • Config# ip host RTR_NAME INT_ADD1 INT_ADD2 INT_ADD3 – Example: ip host lab-a – (for e0, s0, s1)
  • Config# ip domain-lookup – Tell router to lookup domain names
  • Config# ip name-server – Location of DNS server
  • Config# ip domain-name – Domain to append to end of names
  • # clear interface Ethernet 0 – Clears counters on the specified interface
  • # clear counters – Clears all interface counters
  • # clear cdp counters – Clears CDP counters
  • Config# ip route Net_Add SN_Mask Next_Hop_Add – Example: ip route
  • Config# ip route Next_Hop_Add – Default route
  • Config# ip default-network Net_Add – Gateway LAN network
  • Config# ip routing – Enabled by default
  • Config# router rip
  • Config# router igrp 100
  • Config# interface Ethernet 0
  • Config-if# ip address
  • Config-if# no shutdown
  • Config# ipx routing
  • Config# interface Ethernet 0
  • Config# ipx maximum-paths 2 – Maximum equal metric paths used
  • Config-if# ipx network 222 encapsulation sap – Also Novell-Ether, SNAP, ARPA on Ethernet. Encapsulation HDLC on serial
  • Config-if# no shutdown

  • Config# access-list 10 permit – allow all src ip’s on network
  • Config# access-list 10 permit host – specifies a specific host
  • Config# access-list 10 permit any – allows any address
  • Config# int Ethernet 0
  • Config-if# ip access-group 10 in – also available: out
  • Config# access-list 101 permit tcp eq telnet
    -protocols: tcp, udp, icmp, ip (no sockets then), among others
    -source then destination address
    -eq, gt, lt for comparison
    -sockets can be numeric or name (23 or telnet, 21 or ftp, etc)
  • Config# access-list 101 deny tcp any host eq www
  • Config# access-list 101 permit ip any any
  • Config# interface Ethernet 0
  • Config-if# ip access-group 101 out
  • Config# access-list 801 permit 233 AA3 – source network/host then destination network/host
  • Config# access-list 801 permit -1 -1 – “-1” is the same as “any” with network/host addresses
  • Config# interface Ethernet 0
  • Config-if# ipx access-group 801 out
  • Config# access-list 901 permit sap 4AA all 4BB all
    – Permit protocol src_add socket dest_add socket
    -“all” includes all sockets, or can use socket numbers
  • Config# access-list 901 permit any any all any all
    -Permits any protocol with any address on any socket to go anywhere
  • Config# interface Ethernet 0
  • Config-if# ipx access-group 901 in
  • Config# access-list 1000 permit 4aa 3 – “3” is the service type
  • Config# access-list 1000 permit 4aa 0 – service type of “0” matches all services
  • Config# interface Ethernet 0
  • Config-if# ipx input-sap-filter 1000 – filter applied to incoming packets
  • Config-if# ipx output-sap-filter 1000 – filter applied to outgoing packets
  • Config# ip access-list standard LISTNAME
    -can be ip or ipx, standard or extended
    -followed by the permit or deny list
  • Config# permit any
  • Config-if# ip access-group LISTNAME in -use the list name instead of a list number -allows for a larger amount of access-lists
  • Config-if# encapsulation ppp
  • Config-if# ppp authentication chap pap
    -order in which they will be used
    -only attempted with the authentification listed
    -if one fails, then connection is terminated
  • Config-if# exit
  • Config# username Lab-b password 123456
    -username is the router that will be connecting to this one
    -only specified routers can connect
  • Config-if# ppp chap hostname ROUTER
  • Config-if# ppp chap password 123456
    -if this is set on all routers, then any of them can connect to any other
    -set same on all for easy configuration
  • Config# isdn switch-type basic-5ess – determined by telecom
  • Config# interface serial 0
  • Config-if# isdn spid1 2705554564 – isdn “phonenumber” of line 1
  • Config-if# isdn spid2 2705554565 – isdn “phonenumber” of line 2
  • Config-if# encapsulation PPP – or HDLC, LAPD

DDR – 4 Steps to setting up ISDN with DDR

  1. Configure switch type
    Config# isdn switch-type basic-5ess – can be done at interface config
  2. Configure static routes
    Config# ip route – sends traffic destined for to
    Config# ip route bri0 – specifies how to get to network (through bri0)
  3. Configure Interface
    Config-if# ip address
    Config-if# no shutdown
    Config-if# encapsulation ppp

    Config-if# dialer-group 1 – applies dialer-list to this interface
    Config-if# dialer map ip name Lab-b 5551212
    connect to lab-b at 5551212 with ip if there is interesting traffic can also use “dialer string 5551212” instead if there is only one router to connect to
  4. Specify interesting traffic
    Config# dialer-list 1 ip permit any
    Config# dialer-list 1 ip list 101 – use the access-list 101 as the dialer list
  5. Other Options
    Config-if# hold-queue 75 – queue 75 packets before dialing
    Config-if# dialer load-threshold 125 either
    -load needed before second line is brought up
    -“125” is any number 1-255, where % load is x/255 (ie 125/255 is about 50%)
    -can check by in, out, or either
    Config-if# dialer idle-timeout 180
    -determines how long to stay idle before terminating the session
    -default is 120
  • Config# interface serial 0
  • Config-if# encapsulation frame-relay – cisco by default, can change to ietf
  • Config-if# frame-relay lmi-type cisco – cisco by default, also ansi, q933a
  • Config-if# bandwidth 56
  • Config-if# interface serial 0.100 point-to-point – subinterface
  • Config-if# ip address
  • Config-if# frame-relay interface-dlci 100
    -maps the dlci to the interface
    -can add BROADCAST and/or IETF at the end
  • Config-if# interface serial 1.100 multipoint
  • Config-if# no inverse-arp – turns IARP off; good to do
  • Config-if# frame-relay map ip 48 ietf broadcast
    -maps an IP to a dlci (48 in this case)
    -required if IARP is turned off
    -ietf and broadcast are optional
  • Config-if# frame-relay map ip 54 broadcast
  • Show access-lists – all access lists on the router
  • Show cdp – cdp timer and holdtime frequency
  • Show cdp entry * – same as next
  • Show cdp neighbors detail – details of neighbor with ip add and ios version
  • Show cdp neighbors – id, local interface, holdtime, capability, platform portid
  • Show cdp interface – int’s running cdp and their encapsulation
  • Show cdp traffic – cdp packets sent and received
  • Show controllers serial 0 – DTE or DCE status
  • Show dialer – number of times dialer string has been reached, other stats
  • Show flash – files in flash
  • Show frame-relay lmi – lmi stats
  • Show frame-relay map – static and dynamic maps for PVC’s
  • Show frame-relay pvc – pvc’s and dlci’s
  • Show history – commands entered
  • Show hosts – contents of host table
  • Show int f0/26 – stats of f0/26
  • Show interface Ethernet 0 – show stats of Ethernet 0
  • Show ip – ip config of switch
  • Show ip access-lists – ip access-lists on switch
  • Show ip interface – ip config of interface
  • Show ip protocols – routing protocols and timers
  • Show ip route – Displays IP routing table
  • Show ipx access-lists – same, only ipx
  • Show ipx interfaces – RIP and SAP info being sent and received, IPX addresses
  • Show ipx route – ipx routes in the table
  • Show ipx servers – SAP table
  • Show ipx traffic – RIP and SAP info
  • Show isdn active – number with active status
  • Show isdn status – shows if SPIDs are valid, if connected
  • Show mac-address-table – contents of the dynamic table
  • Show protocols – routed protocols and net_addresses of interfaces
  • Show running-config – dram config file
  • Show sessions – connections via telnet to remote device
  • Show startup-config – nvram config file
  • Show terminal – shows history size
  • Show trunk a/b – trunk stat of port 26/27
  • Show version – ios info, uptime, address of switch
  • Show vlan – all configured vlan’s
  • Show vlan-membership – vlan assignments
  • Show vtp – vtp configs

I hope you found this article to be of use and it helps you prepare for your Cisco CCNA certification. I am sure you will quickly find out that hands-on real world experience is the best way to cement the CCNA concepts in your head to help you pass your CCNA exam!