Commands for CCNA
debug eigrp fsm
Command using to examine some of the output from EIGRP's FSM. Use this command to examine what DUAL does when a route is removed from the routing table.
ping traceroute show ip route show ip interface brief show cdp neighbors detail
Common IOS troubleshooting commands include:
Step 1. Enable DHCP snooping using the ip dhcp snooping global configuration mode command. Step 2. Enable DHCP snooping for specific VLANs using the ip dhcp snooping vlan number command. Step 3. Define ports as trusted at the interface level by defining the trusted ports using the ip dhcp snooping trust command. Step 4. (Optional) Limit the rate at which an attacker can continually send bogus DHCP requests through untrusted ports to the DHCP server using the ip dhcp snooping limit rate rate command.
How to configure DHCP snooping on switch
ip route network mask {next-hop-ip | exit-intf}
IPv4 static routes are configured in global configuration command
encapsulation hdlc
If the default encapsulation method has been changed, use the command in privileged EXEC mode to re-enable HDLC.
ip dhcp pool pool_name
creates a dhcp pool with the specified name and puts the router in DHCPv4 configuration mode
ipv6 dhcp pool pool_name
creates a pool and enters the router in DHCPv6 configuration mode, which is identified by the Router(config-dhcpv6)# prompt.
spanning-tree bpduguard enable
enables BPDU guard
spanning-tree portfast bpduguard default
enables BPDU guard on all PortFast-enabled ports.
IPv6 unicast-routing
enables IPv6 routing
spanning-tree portfast default
enables PortFast on all nontrunking interfaces.
no access-list
enter in global mode to remove entire access list
ip helper-address ip_address
enter in interface mode to configure dhcpv4 relay
ipv6 dhcp relay destination ip_address
enter in interface mode to configure dhcpv6 relay
no ip access-group
enter in interface mode to remove interface from access list
Router(config-if)# no ipv6 nd managed-config-flag Router(config-if)# no ipv6 nd other-config-flag
enter in interface mode, to re-enable an interface for SLAAC(Stateless Address Autoconfiguration) that might have been set to another option
interface port-channel identifier_number
enter port channel interface configuration mode
show ipv6 ospf
examine the OSPFv3 process ID and router ID.
debug ip nat detailed
generates a description of each packet considered for translation. This command also provides information about certain errors or exception conditions, such as the failure to allocate a global address.
show spanning-tree vlan vlan_id
get STP information for a particular VLAN. Use this command to get information about the role and status of each port on the switch.
enable or en
go to Privileged EXEC Mode
R1 (config) # interface g0/0.subinterface_number R1 (config-subif) # encapsulation dot1q vlan_id R1 (config-subif) # ip address 172.17.10.1 255.255.255.0 R1 (config-subif) # interface g0/0 R1 (config-if) # no shutdown
how to configure subinterfaces on router The subinterface number is configurable, but it typically reflects the VLAN number.
no auto-summary
no longer summarizes networks to their classful address at boundary routers
enable password
older one, less secure
clear ip nat translation *
privileged EXEC command to clear all translations from the table. Note: Only the dynamic translations are cleared from the table. Static translations cannot be cleared from the translation table.
redistribute static
propagate that route throughout the EIGRP domain. tells EIGRP to include static routes in its EIGRP updates to other routers. Configure on router configuration mode
show interfaces etherchannel
provide information about the role of the interface in the EtherChannel
show ipv6 route ospf
provides specifics about OSPFv3 routes in the routing table.
service dhcp
re-enable the DHCPv4 server
S1# configure terminal S1 (config-if) # interface interface_id S1 (config-if) # no switchport access vlan S1 (config-if) # end
remove VLAN assignment
no interface port-channel channel_id
remove entire etherchannel
no ip ospf dead-interval
reset OSPFv2 dead interval seconds
no ip ospf hello-interval
reset OSPFv2 hello interval seconds
no ipv6 ospf dead-interval
reset OSPFv3 dead interval seconds
no ipv6 ospf hello-interval
reset OSPFv3 hello interval seconds
show ip route show ip route static show ip route network show running-config | section ip route
show routing table show static routing table show specific routing table for the destination ip show ip route setting on running-config
show span
show spanning-tree protocols
show frame-relay lmi
show the Local Management Interface (LMI) of Frame Relay - The output shows the LMI type used by the Frame Relay interface and the counters for the LMI status exchange sequence, including errors such as LMI timeouts.
show cdp neighbors & show cdp neighbors
show which int connect to which name and int of devices
show ip nat translations
shows active NAT translations
show etherchannel summary
simply display one line of information per port channel
Switch(config)# interface range type module/first-number - last-number
t is simple to make configuration changes to multiple ports on a switch. If a range of ports must be configured, use the interface range command.
configure terminal or conf t
take the device from privileged EXEC mode to the global configuration mode
clock set ?
the IOS displays what command arguments or variables can be next, and provides an explanation of each
dns-server ip_address
the IPv4 address of the DNS server that is available to a DHCPv4 client
show ip ospf interface
the quickest way to verify OSPF interface settings
default-router ip_address
to define the default gateway router for dhcp
ipv6 eigrp as_number
to enable eigrp on an interface
security passwords min-length
to ensure that all configured passwords are a minimum of a specified length
ip ospf priority value_number
to set the OSPFv2 priority of an interface
ipv6 ospf priority value_number
to set the OSPFv3 priority of an interface
show access-list
to show the access list you created
show frame-relay map
to show the map of Frame Relay
netbios-name-server address [address2...address8]
used to define the NetBIOS WINS server for dhcp
domain-name domain
used to define the domain name for dhcp
show ip ospf
used to examine the OSPF process ID and router ID
show ip dhcp server statistics
used to verify that messages are being received or sent by the router. This command displays count information regarding the number of DHCPv4 messages that have been sent and received.
show ntp status
user EXEC command can be used to display such information as the NTP synchronization status, the peer that the device is synchronized to, and in which NTP strata the device is functioning.
show ipv6 dhcp interface
verifies the interface is in relay mode with ipv6_address destination configured as the DHCPv6 server.
show ipv6 dhcp pool
verifies the name of the DHCPv6 pool and its parameters.
ping
verify connectivity
show ipv6 route
verify that IPv6 networks and specific IPv6 interface addresses have been installed in the IPv6 routing table
clear ip nat statistics
verify that the NAT translation is working, it is best to clear statistics from any past translations before testing
show ipv6 protocols
verify that the OSPFv3
show ip ospf neighbor
verify that the router has formed an adjacency with its neighboring routers on OSPFv2
show ipv6 ospf neighbor
verify that the router has formed an adjacency with its neighboring routers on OSPFv3
show glbd
verify the Gateway Load Balancing Protocol (GLBP) status
show ip ospf interface interface_id
verify the current OSPF cost assigned to the interface
debug ip nat
verify the operation of the NAT feature by displaying information about every packet that is translated by the router
show ip eigrp neighbors
view the neighbor table and verify that EIGRP has established an adjacency with its neighbors.
ipv6 rip domain-name enable
enable RIPng on interface for ipv6
show bootvar
(show boot in older IOS versions) to see what the current IOS boot file is set to.
bandwidth 100
Adjusting the Interface Bandwidth for OSPF and EIGRP interfaces in kilobits
no bandwidth
Adjusting the Interface Bandwidth for OSPF and EIGRP interfaces in kilobits to default
copy running-config startup-config
After being executed, the running configuration file updates the startup configuration file.
banner motd # message #
Although requiring passwords is one way to keep unauthorized personnel out of a network, it is vital to provide a method for declaring that only authorized personnel should attempt to gain entry into the device. To do this, add a banner to the device output.
reload
Assuming that we have not overwritten the startup configuration with the changes, we can replace the running configuration with the startup configuration by using this command.
frame-relay lmi-type [cisco | ansi | q933a]
Based on the LMI status messages it receives from the Frame Relay switch, the router automatically configures its interface with the supported LMI type acknowledged by the Frame Relay switch. If it is necessary to set the LMI type, use the command. Configuring the LMI type disables the autosense feature.
eigrp log-neighbor-changes
By Default is enable. On router configuration mode command is enabled.This command is used to: 1) Display any changes in EIGRP neighbor adjacencies. 2) Help verify neighbor adjacencies during configuration of EIGRP. 3) Advise the network administrator when any EIGRP adjacencies have been removed.
logging console - logging buffered
By default, Cisco routers and switches send log messages for all severity levels to the console. On some IOS versions, the device also buffers log messages by default. To enable these two settings, use the commands on global configuration mode
ip nat translation timeout timeout_seconds
By default, NAT translation entries time out after 24 hours, unless the timers have been reconfigured
Router(config)# line vty 0 4 Router(config-line )# exec-timeout 10
By setting the exec timeout, you are telling the Cisco device to automatically disconnect users on a line after they have been idle for the duration of the exec timeout value. Exec timeouts can be configured on console, vty, and aux ports. This command will disconnect users after 10 minutes.
maximum-paths value
Cisco IOS, by default, allows EIGRP load balancing using up to four equal-cost paths; however, this can be modified on router configuration mode command. If the value is set to 1, load balancing is disabled.
show ip ospf interface brief
Command is useful to display a summary and status of OSPF-enabled interfaces.
S1(config)# interface f0/6 S1(config-if)# no switchport S1(config-if)# ip address 192.168.200.1 255.255.255.0 S1(config-if)# no shutdown S1(config-if)# end
Configure routed ports by putting the interface into Layer 3 mode with the no switchport interface configuration command. Then assign an IP address to the port. That's it!
ipv6 dhcp server pool_name
Configure the DHCPv6 Interface Interface configuration mode command binds the DHCPv6 pool to the interface.
summary-address address mask
Configured external route summarization on ASBRs on router configuration mode command.
ipv6 router ospf process_id
Configuring the OSPFv3
show ip route ospf
Display all routers learned through OSPFv2 from routing table
show ppp multilink
Display information about a ppp multilink interface
show mac-address-table
Displays all MAC addresses that the switch has learned, how those addresses were learned (dynamic/static), the port number, and the VLAN assigned to the port.
show protocols
Displays information about the routed protocol that is enabled, and the protocol status of interfaces.
show running-config interface interface-id
Displays the commands configured on the specified interface.
Router# show ssh
Displays the status of SSH server connections.
Router# show ip ssh
Displays the version and configuration data for SSH.
clear access-list counters access-list_ID/Name
During testing of an ACL, the counters can be cleared using this command
variance value
EIGRP for IPv4 and IPv6 can also balance traffic across multiple routes that have different metrics. This type of balancing is called unequal-cost load balancing. Command in router configuration mode enables EIGRP to install multiple loop-free routes with unequal cost in a local routing table.
clear ip nat translation
EXEC mode command. It is useful to clear the dynamic entries when testing the NAT configuration.
R3# configure terminal _ R3(config)# interface serial 0/0/0 - R3(config-if)# encapsulation ppp
Enabling PPP on an Interface. Remember that if PPP is not configured on a Cisco router, the default encapsulation for serial interfaces is HDLC.
Router(config)# interface loopback number Router(config-if)# ip address ip-address subnet-mask Router(config-if)# exit
Enabling and assigning a loopback address
frame-relay map protocol protocol-address dlci [broadcast] [ietf] [cisco]
Establishing Frame Relay static mapping depends on your network needs. To map between a next hop protocol address and DLCI destination address, use this command - Use the keyword ietf when connecting to a non-Cisco router.
Step 1: ip domain-name domain-name Step 2: crypto key generate rsa general-keys modulus modulus-size Step 3: Create a local database username entry using the username name secret secret global configuration command. Step 4: Enable vty inbound SSH sessions using the line vty commands login local and transport input ssh.
It is possible to configure a Cisco device to support SSH using four steps Just note that the modulus determines the size of the key and can be configured from 360 bits to 2048 bits. The larger the modulus, the more secure the key, but the longer it takes to encrypt and decrypt information. The minimum recommended modulus length is 1024 bits.
debug ppp authentication
Never assume your authentication configuration works without testing it. Debugging allows you to confirm your configuration and correct any deficiencies. For debugging PPP authentication, use the command.
interface interface_id ipv6 ospf process_id area area_id
OSPFv3 configure directly on the interface instead of using network command router configuration mode command
show ip route
On a Cisco IOS router, this command can be used to display the routing table of a router.
route print or netstat -r
On a Windows host, those commands can be used to display the host routing table. Both commands generate the same output. The output may seem overwhelming at first, but is fairly simple to understand.
delete vlan.dat
On a switch you must also issue the delete vlan.dat command in addition to the erase startup-config command in order to return the device to its default "out-of-the-box" configuration (comparable to a factory reset)
keepalive
On interface configuration command. By default, the keepalive time interval is 10 seconds on Cisco serial interfaces. You can change the keepalive interval. The LMI status exchange messages determine the status of the PVC connection. A large mismatch in the keepalive interval on the router and the switch can cause the switch to declare the router dead.
metric weights tos k1 k2 k3 k4 k5
On router configuration mode command. To change EIGRP composite metric. Modifying the metric weights value is generally not recommended.
show ip route show interfaces show ip interface
Other interface verification commands: 1) Displays the contents of the IPv4 routing table stored in RAM. 2) Displays statistics for all interfaces on the device. 3) Displays the IPv4 statistics for all interfaces on a router.
show run | begin [interface interface-id]
Sticky MAC addresses are added to the MAC address table and to the running configuration.
crypto key zeroize rsa
To delete the RSA key pair. After the RSA key pair is deleted, the SSH server is automatically disabled.
ip hello-interval eigrp as_number seconds
The command to configure a different Hello interval for ipv4 EIGRP on interface configuration mode
ipv6 hold-time eigrp as_number seconds
The command to configure a different Hello interval for ipv6 EIGRP on interface configuration mode
ip hold-time eigrp as_number seconds
The command to configure a different Hold time for ipv4 EIGRP on interface configuration mode
ipv6 hello-interval eigrp as_number seconds
The command to configure a different Hold time for ipv6 EIGRP on interface configuration mode
description Link to LAN -0
The description text is limited to 240 characters. On production networks, a description can be helpful in troubleshooting by providing information about the type of network that the interface is connected to and if there are any other routers on that network.
lease { days [hours] [minutes] | infinite}
The duration of the DHCPv4 lease can be changed
debug ip packet
The extended ACL is used with this command to debug
channel-group identifier_number mode active
The identifier specifies a channel group number. The mode active keywords identify this as an LACP EtherChannel configuration.
service password-encryption
This command causes the encryption of passwords to occur when a password is configured. The purpose of this command is to keep unauthorized individuals from viewing passwords in the configuration file.
show ip dhcp binding
This command displays a list of all IPv4 address to MAC address bindings that have been provided by the DHCPv4 service.
show version
This command displays information about the currently loaded IOS version, along with hardware and device information.
spanning-tree vlan vlan_id priority value
This command gives more granular control over the bridge priority value. The priority value is configured in increments of 4,096 between 0 and 61,440.
debug ip dhcp server events
This command reports server events, like address assignments and database updates. It is also used for decoding DHCPv4 receptions and transmissions.
login block-for 120 attempts 3 within 60
This command will block login attempts for 120 seconds, if there are three failed login attempts within 60 seconds.
Switch(config)# line vty 0 15 Switch(config-line)# password cisco Switch(config-line)# login
This prevents Telnet access to the device without authentication.
Switch(config)# line console 0 Switch(config-line)# password cisco Switch(config-line)# login
This reduces the chance of unauthorized personnel physically plugging a cable into the device and gaining device access. The console user will be prompted to enter a password before gaining access to the CLI.
ntp server ip-address
To allow the software clock to be synchronized by an NTP time server. use in global configuration mode
switchport port-security violation {protect | restrict | shutdown}
To change the violation mode on a switch port.
clear frame-relay inarp
To clear dynamically created Frame Relay maps that are created using Inverse ARP
ipv6 summary-address eigrp as_number prefix/prefix_length
To configure EIGRP for IPv6 manual summarization on a specific EIGRP interface, use the following interface configuration mode command:
ip default-gateway 192.168.10.1
To configure a default gateway on a switch
ipv6 route ::/0 {ipv6-address | interface-type interface-number}
To configure a default static IPv6 route
ntp master [stratum]
To configure a device as having an NTP master clock to which peers can synchronize themselves. use in global configuration mode
ip route 0.0.0.0 0.0.0.0 {exit-intf | next-hop-ip}
To configure an IPv4 default static route
R3(config)# interface serial 0/0/0 - R3(config-if)# encapsulation ppp - R3(config-if)# compress [ predictor | stac ]
To configure compression over PPP, enter the following commands:
ipv6 bandwidth-percent eigrp as-number percent
To configure the percentage of bandwidth that can be used by EIGRP for IPv6 on an interface
traffic-share balanced
To control how EIGRP traffic is distributed among routes when there are multiple routes for the same destination network that have different costs. Traffic is then distributed proportionately to the ratio of the costs.
router ?
To determine which routing protocols are supported by the IOS
no cdp run
To disable CDP globally, use the global configuration command
no cdp enable
To disable CDP on an interface, use the interface command
show port-security [interface interface-id]
To display port security settings for the switch or for the specified interface
show ntp associations
To display the status of NTP associations. use in privileged EXEC mode
show ip interface brief
To display the usability status of interfaces configured for various IP addresses, use the show ip interface brief command in privileged EXEC mode.
ip ospf message-digest-key key md5 password ip ospf authentication message-digest interface
To enable MD5 authentication for OSPF on a per-interface basis, configure: on interface configuration mode command. on interface configuration mode command.
ip ospf message-digest-key key md5 password area area-id authentication message-digest router
To enable OSPF MD5 authentication globally, configure: on interface configuration mode command. on configuration mode command.
sdm prefer lanbase-routing
To enable the routing functionality on the 2960 switch in global configuration mode
erase NVRAM:startup-config erase startup-config
To erase the startup configuration file
ip summary-address eigrp as_number network_address subnet_mask
To establish EIGRP manual summarization on a specific EIGRP interface, use the following interface configuration mode command
area area_id range address mask
To manually configure interarea route summarization on an ABR (OSPFv2) on router configuration mode command.
area area_id range prefix/prefix_length.
To manually configure interarea route summarization on an ABR (OSPFv3) on router configuration mode command.
Router(config-if)# ipv6 nd other-config-flag
To modify the RA(Router Advertisement) message sent on the interface of a router to indicate stateless DHCPv6. The stateless DHCPv6 option informs the client to use the information in the RA message for addressing, but additional configuration parameters are available from a DHCPv6 server.
Router(config-if)# ipv6 nd managed-config-flag
To modify the RA(Router Advertisement) message sent on the interface of a router to signify stateful DHCPv6:
_ _ _ - _ _ Router(config)# boot system flash0://c1900-universalk9-mz.SPA.152-4.M3.bin _ Router(config)# boot system tftp://c1900-universalk9-mz.SPA.152-4.M3.bin _ no boot system
To upgrade to the copied IOS image after that image is saved on the router's flash memory, configure the router to load the new image during bootup. command is a global configuration command that allows the user to specify the source for the Cisco IOS Software image to load. Specify the flash device as the source of the Cisco IOS image. _ Specify the TFTP server as a source of Cisco IOS image. _ _ commands in the configuration, the router defaults to loading the first valid Cisco IOS image in flash memory and running it.
show standby
To verify Hot Standby Router Protocol (HSRP) state
cd nvram pwd dir
To view the contents of NVRAM, you must change the current default file system
show ip ospf database
Verify Link-State Database of OSPF (LSDB)
show port-security address
Verify Secure MAC Addresses To display all secure MAC addresses configured on all switch interfaces, or on a specified interface with aging information for each
Router(config)# key chain name-of-chain _ _ _ Router(config-keychain)# key key-id _ _ _ _ _ Router(config-keychain-key )# key-string key-string-text _ _ _ Router(config)# interface type number _ Router(config-if)# ip authentication mode eigrp as-number md5 _ Router(config-if)# ip authentication key-chain eigrp as-number name-of-chain
a. In global configuration mode, create the keychain. Although multiple keys can be configured, this section focuses on the use of a single key. _ b. Specify the key ID. The key ID is the number used to identify an authentication key within a keychain. The range of keys is from 0 to 2,147,483,647. It is recommended that the key number be the same on all routers in the configuration. _ c. Specify the key string for the key. The key string is similar to a password. Routers exchanging authentication keys must be configured using the same key string. _ Configure EIGRP to perform message authentication with the previously defined key. Complete this configuration on all interfaces enabled for EIGRP. _ _ Specify the keychain that should be used for authentication. The name-of-chain argument specifies the keychain that was created previously.
ip ospf cost 647
alternative to setting the default interface bandwidth, the cost can be manually configured on an interface
spanning-tree vlan vlan_id root primary
assigned as the primary root bridge
ip ssh time-out 60
auto logout idle for 60 second on ssh
auto-cost reference-bandwidth 100
change reference bandwidth to 100Mb/s on OSPF domain
show running-config | include no service dhcp
check the dhcp server is not disable on router
show interface trunk
check the status of the trunk ports on the switches
no hostname
command caused the device to revert to the default hostname.
show ip protocols
command displays the IPv4 routing protocol settings currently configured on the router.
show ipv6 ospf interface brief
command displays the active OSPFv3 interfaces
show frame-relay pvc
command displays the status of all the PVCs configured on the router. You can also specify a particular PVC.
clock set 19:50:00 ?
command explanation with more than one argument or variable option
show snmp community
command output does not display information relating to the SNMP community string or, if applicable, the associated ACL.
enable secret password
command provides greater security because the password is encrypted
ip bandwidth-percent eigrp as_number percent
command to configure the percentage of bandwidth that can be used by EIGRP on an interface. By default, EIGRP uses only up to 50 percent of an interface's bandwidth for ipv4 EIGRP information.
debug frame-relay lmi
command to determine whether the router and the Frame Relay switch are sending and receiving LMI packets properly. - Look at the figure to examine the output of an LMI exchange. -out is an LMI status message sent by the router. -in is a message received from the Frame Relay switch. -A full LMI status message is a type 0. -An LMI exchange is a type 1. -dlci 102, status 0x2 means that the status of DLCI 102 is active. - The possible values of the status field are as follows: -0x0 - The switch has this DLCI programmed, but for some reason it is not usable. The reason could possibly be the other end of the PVC is down. -0x2 - The Frame Relay switch has the DLCI and everything is operational. -0x4 - The Frame Relay switch does not have this DLCI programmed for the router, but that it was programmed at some point in the past. This could also be caused by the DLCIs being reversed on the router, or by the PVC being deleted by the service provider in the Frame Relay cloud.
clear counters
command to reset the PVC statistics counters. Wait 5 or 10 minutes after clearing the counters before issuing the show commands again. Note any additional errors. If you need to contact the carrier, these statistics help in resolving the issues.
terminal length number
command to specify the number of lines to be displayed. A value of 0 (zero) prevents the router from pausing between screens of output.
show frame-relay pvc [interface interface] [dlci]
command to view PVC and traffic statistics. This command is also useful for viewing the number of BECN and FECN packets received by the router. The PVC status can be active, inactive, or deleted.
show snmp
command, as it displays the information that is commonly of interest when examining the SNMP configuration. Unless there is an involved SNMPv3 configuration, for the most part the other command options only display selected portions of the output of the commands
ip route 0.0.0.0 0.0.0.0 interface interface_id
configuration of an IPv4 default static route
ip ospf dead-interval 20
configure OSPFv2 dead interval to 20 seconds
ip ospf hello-interval 5
configure OSPFv2 hello interval to 5 seconds
ipv6 ospf dead-interval 20
configure OSPFv3 dead interval to 20 seconds
ipv6 ospf hello-interval 5
configure OSPFv3 hello interval to 5 seconds
ipv6 ospf process_id area area_id
configure OSPFv3 on interfaces
R1(config)# access-list 1 permit 192.168.10.0 0.0.0.255 R1(config)# interface interface_id R1(config-if)# ip access-group 1 out
configure access list with number and apply it on specific interface
spanning-tree portfast
configure as a edge ports that will never have a switch connected to it and immediately transitions to forwarding
ppp authentication pap/chap
configure authentication over ppp by using pap or chap on serial interfaces
ip dhcp excluded-address ip_address/ip_address from low to high for range
configure dhcp excluded addresses
ip access-list standard NO_ACCESS
configure ip access list for name with NO_ACCESS
ipv6 access-list NAME
configure ipv6 access list with NAME name
ipv6 address fe80::1 link-local
configure link local address on router
router ospf process-id network
configure ospf
auto-cost reference-bandwidth ref-bw
configure reference badwidth for OSPF in Mb/s
ip address dhcp
configure router interface as dhcpv4 client on interface mode
ipv6 enable ipv6 address autoconfig
configure router interface as dhcpv6 client on interface mode
ip route 192.168.1.0 255.255.255.0 interface interface_id/next hop address or ip route 192.168.1.0 255.255.255.0 interface interface_id next hop address
configure static route
hostname Sw-Floor-1 or ho Sw-Floor-1
configure the host name of device to Sw-Floor-1
passive-interface interface_id
configure the interface to passive interface on OSPF
S1(config)# vlan vlan_id S1(config-vlan)# name vlan_name S1(config-vlan)# exit S1(config)# interface interface_id S1(config-if)# switchport mode access S1(config-if)# switchport access vlan vlan_id
configure the switch port to the vlan
spanning-tree vlan vlan_id root secondary
configured as the secondary root bridge. This ensures that the alternate switch becomes the root bridge if the primary root bridge fails.
access-class access-list_number in/out
configured in vty line configuration mode restricts incoming and outgoing connections
show ipv6 interface brief
confirms that the correct global IPv6 addresses have been successfully configured and that the interfaces are enabled
debug ipv6 dhcp detail
debug command to view detailed ipv6 dhcp packets
S1# conf t S1 (config-if) # no vlan vlan_id S1 (config-if) # end
delete a VLAN
no ip access-list extended extended_name
delete entire extended ACL in global configuration command.
no service dhcp
disable DHCPv4 server
no cdp run
disable the use of CDP (Cisco Discovery Protocol) on devices or ports that do not need to use it
ip ssh authentication-retries 2
disconnect after 2 fail input password on ssh
cl?
display a list of commands or keywords that start with the characters cl
show etherchannel port-channel
display information about a specific port channel interface
show vlan brief
display the contents of the vlan.dat file.
show ip eigrp topology all-links
displayed EIGRP topology table of all links whether they satisfy the FC (Feasible Condition) or not.
show ip nat translations verbose
displays additional information about each NAT translation, including how long ago the entry was created and used.
show ip dhcp conflict
displays all address conflicts recorded by the DHCPv4 server
show ipv6 dhcp conflict
displays any address conflicts logged by the stateful DHCPv6 server.
show ip nat statistics
displays information about the total number of active translations, NAT configuration parameters, the number of addresses in the pool, and the number of addresses that have been allocated.
show running-config | section dhcp
displays the DHCPv4 commands configured on running-config
show interface port-channel
displays the general status of the port channel interface
show ipv6 interface gigabitethernet 0/0
displays the interface status and all of the IPv6 addresses belonging to the interface
Ctrl + Z
moving from any configuration mode all the way back to privileged EXEC mode
end
moving from any configuration mode all the way back to privileged EXEC mode
disable
return from the privileged EXEC to the user EXEC mode
passive-interface default
set all interfaces to passive interface on OSPF
show ip eigrp topology
show EIGRP topology table
show ip arp
show Resolution Protocol Address on Cisco Router
arp -a
show Resolution Protocol Address on PC
show running-config | section interface interface_id
show ip helper-address on interface
show file systems
which lists all of the available file systems on a Cisco 1941 router, in this example. This command provides useful information such as the amount of available and free memory, the type of file system, and its permissions. Permissions include read only (ro), write only (wo), and read and write (rw), shown in the Flags column of the command output.