CCNA 3 Commands List

CCNA3 Commands List

Here is the detailed list of CCNA3 commands:


The default port costs are defined by the speed at which the port operates (ex: 100Mbps have a port cost of 19).

To configure the port cost of an interface:

SW1(config-if)# spanning-tree cost value

value can be between 1 and 200,000,000. The port with the lowest value is selected.


To restore the port cost back to the default value of 19:

SW1(config-if)# no spanning-tree cost

To change the port priority on a certain port:

SW1(config)# interface f0/4        

SW1(config-if)# spanning-tree vlan 500 port-priority 64

Where the port-priority value is an increment of 16 between 0 and 128, the default value is 128.


To verify the port and path cost to the root bridge:

SW1(config)# show spanning-tree

To verify the various states  of a port:

SW1(config)# show spanning-tree summary


To configure a RSTP or PVST+ PortFast  edge port which immediately transitions to the forwarding state:

SW1(config-if)# spanning-tree portfast


To enable the portfast on all nontrunking interfaces:

SW1(config)# spanning-tree portfast default


To show the link type that determines whether the port can immediately transition to forwarding state:

SW1(config)# spanning-tree link-type


To configure a switch as root bridge:

SW1(config)# spanning-tree vlan  10 root primary


SW1(config)# spanning-tree vlan 10 priority 4,096

value is configured in increments of 4,096 between 0 and 61,440. The default value is 32,768.


To configure an alternate root bridge:

SW1(config)# spanning-tree vlan vlanid root secondary

To configure the BPDU guard that puts the port in an error-disabled state on receipt of a BPDU:

SW1(config-if)# spanning-tree bpduguard enable

To enable the bpduguard on all port-fast enabled ports:

SW1(config)# spanning-tree portfast bpduguard default

To show the spanning-tree of the active interfaces only:

SW1(config)# show spanning-tree active

Configure Rapid-pvst+ mode, specify an interface to configure with link type and clear all detected STP.

S1(config)# spanning-tree mode rapid-pvst

S1(config)# interface f0/2

S1 (config-if)# spanning-tree link-type point-to-point

S1 (config-if)# end

S1# clear spanning-tree detected-protocols

SW1(config)# show spanning-tree vlan 10


R1(config)# show standby

R1(config)# int f0/0

R1(config-if)# ip address

R1(config)# standby 1 ip

R1(config)# no shutdown

To assign a priority to a router to become the active router noting that the standard value is 100:

R1(config)# standby 1 priority 110

To re-assign the initial router its initial role

R1(config)# standby preempt

R1# show glbp

Link aggregation configuration:

SW1(config)# interface range f0/1-4

SW1(config-range)# channel-group 1 mode active

SW1(config)# interface port-channel 1

SW1(config-port)# switchport mode trunk

SW1(config-port)# switchport trunk native vlan 90

SW1(config-port)# switchport trunk allowed vlan 1, 10, 90


To display the general status of the port channel interface

S1# show interface port-channel1

To display one line of information per port channel

S1# show etherchannel summary

To display information about a specific port channel interface

S1# show etherchannel port-channel 

To display information about the role of the interface in the EtherChannel

S1# show interfaces f0/1 etherchannel 

OSPF Configuration

R1(config)# Router ospf 10

R1(config-router)# Router-id

R1(config-router)# Network area 0

R1(config-router)# Network area 0

R1(config-router)# auto-cost reference-bandwidth 1000

R1(config-router)# passive-interface g0/0

R1(config)# interface G0/0

R1(config-if)# bandwidth 1000000

R1(config-if)# ip ospf priority 255

To verify that the router has formed an adjacency with its neighboring routers

R1# show ip ospf neighbor

To verify vital OSPF configuration information

R1# show ip protocols

To display the OSPF process ID and router ID as well as the OSPF SPF and OSPF area information

R1# show ip ospf

To display a summary and status of OSPF-enabled interfaces

R1# show ip ospf interface brief

To provide a detailed list for every OSPF-enabled interface

R1# show ip ospf interface

Reset the OSPF process

R1# clear ip ospf process

Distribute the static into the routing table

R1(config)# ip route g0/0

R1(config)# default-information originate

R1# show ip route

OSPF Hello and Dead intervals can be modified manually using the following interface configuration mode commands:

ip ospf hello-interval 10

ip ospf dead-interval 40

To reset the intervals to their default

no ip ospf hello-interval

no ip ospf dead-interval

To enable OSPF MD5 authentication globally, configure:

R1(config)# area 0 authentication message-digest

R1(config)# int g0/0

R1(config-if)# ip ospf message-digest-key 1 md5 password 

To enable OSPF MD5 authentication on each interface, configure:

R1(config)# int g0/0

R1(config-if)# ip ospf message-digest-key 1 md5 password 

R1(config-if)# ip ospf authentication message-digest

R1# show ip ospf interface serial 0/0/0






EIGRP Configuration:

Router(config)# router eigrp autonomous-system

Router(config-router)# eigrp router-id ipv4-address

show ip protocols

show ip eigrp neighbors

show ip eigrp topology

Router(config-router)# network network-address [wildcard-mask]

Router(config-router)# passive-interface interface-type interface-number

Enable, disable automatic summarization:

Router(config-router)# auto-summary

Router(config-router)# no auto-summary

Manual Summarization:

Router(config)# interface Serial0/0/0

Router(config-if)# ip summary-address eigrp 1

Propagation of a static route

Router(config)# router eigrp 1

Router(config-router)# redistribute static


Changing the metrics

R1(config)# interface s0/0/0

R1(config-if)# ip hello-interval eigrp 1 10     // time in seconds

R1(config-if)# ip hold-time eigrp 1 30

Router(config)# interface g0/0

Router(config-router)# delay 100   ///unit is ms

Router(config-router)# bandwidth 1000   ///unit is kbps


The composite metric calculation: (where k1=k3=1 and k2=k4=k5=0)

((10⁷/min (BW) (in Kbps)) +∑DLY (in ԋs)/10)*256


Router(config)#key chain mykey                         //configure key chain name mykey
Router(config-keychain)#key 1                          // Specifies the key number
Router(config-keychain-key)#key-string cisco  //Specifies the authentication string for a key.

Router(config)#interface fa0/0
Router(config-if)#ip authentication mode eigrp 1 md5
Router(config-if)#ip authentication key-chain eigrp 1 mykey


Conversion :


Subnet mask /19 can be converted to binary 11111111.11111111.11100000.00000000 and to dotted decimal

The wildcard mask is – =


Subnet mask /28 can be converted to binary 11111111.11111111.11111111.11110000 and to decimal

The wild card mask is –