We can have EXEC Mode, Privileged EXEC Mode, Global Configuration Mode, Interface Configuration.
# User EXEC Mode# This is the initial mode after logging in. Limited to basic monitoring commands.Switch># Privileged EXEC Mode# Provides access to all monitoring commands and some configuration commands. Use 'enable' to enter this mode from User EXEC Mode.Switch> enableSwitch## Global Configuration Mode# Allows configuration changes to the device. Use 'configure terminal' to enter this mode from Privileged EXEC Mode.Switch# configure terminalSwitch(config)## Interface Configuration Mode# Used to configure specific interfaces (e.g., VLANs, Ethernet ports). Enter this mode from Global Configuration Mode.Switch(config)# interface vlan 1Switch(config-if)## Line Configuration Mode# Used to configure console, AUX, and VTY (Telnet/SSH) lines. Enter this mode from Global Configuration Mode.Switch(config)# line console 0Switch(config-line)## To return to Global Configuration Mode from a sub-mode (e.g., Interface or Line Configuration Mode)Switch(config-if)# exitSwitch(config)## To return to Privileged EXEC Mode from Global Configuration ModeSwitch(config)# exitSwitch## To return to User EXEC Mode from Privileged EXEC ModeSwitch# disable
startup-config: This is the saved configuration file stored in NVRAM. It contains all the commands that the device will use on startup or reboot. Flash does not lose its content when the device is powered off.
running-config: This is stored in Random Access Memory (RAM). It reflects the current configuration. Modifying a running configuration affects the operation of a Cisco device immediately. RAM is volatile and loses all content when the device is powered off or restarted.
To save the running configuration to the startup configuration:
At this point, the routers have their basic configurations. The next step is to configure their interfaces because end devices cannot reach the routers until the interfaces are configured. There are many different types of interfaces for Cisco routers. For example, the Cisco ISR 4321 router is equipped with two Gigabit Ethernet interfaces:
GigabitEthernet 0/0/0 (G0/0/0)
GigabitEthernet 0/0/1 (G0/0/1)
Configuring a router interface is very similar to configuring a management SVI on a switch. Specifically, it involves issuing the following commands:
Router(config)# interface type-and-number #example: interface s0/0/0 Router(config-if)# description description-text Router(config-if)# ip address 192.68.101.2 255.255.255.0Router(config-if)# ipv6 address ipv6-address/prefix-length Router(config-if)# no shutdown
Example:
R1> enableR1# configure terminalEnter configuration commands, one per line.End with CNTL/Z.R1(config)# interface gigabitEthernet 0/0/0R1(config-if)# description Link to LANR1(config-if)# ip address 192.168.10.1 255.255.255.0R1(config-if)# ipv6 address 2001:db8:acad:10::1/64R1(config-if)# no shutdownR1(config-if)# exitR1(config)#*Aug 1 01:43:53.435: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to down*Aug 1 01:43:56.447: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to up*Aug 1 01:43:57.447: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/0, changed state to upR1(config)#R1(config)# interface gigabitEthernet 0/0/1R1(config-if)# description Link to R2R1(config-if)# ip address 209.165.200.225 255.255.255.252R1(config-if)# ipv6 address 2001:db8:feed:224::1/64R1(config-if)# no shutdownR1(config-if)# exitR1(config)#*Aug 1 01:46:29.170: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/1, changed state to down*Aug 1 01:46:32.171: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/1, changed state to up*Aug 1 01:46:33.171: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0/1, changed state to upR1(config)#
Verify the configuration:
show ip interface brief
R1# show ip interface briefInterface IP-Address OK? Method Status ProtocolGigabitEthernet0/0/0 192.168.10.1 YES manual up upGigabitEthernet0/0/1 209.165.200.225 YES manual up upVlan1 unassigned YES unset administratively down downR1# show ipv6 interface briefGigabitEthernet0/0/0 [up/up] FE80::201:C9FF:FE89:4501 2001:DB8:ACAD:10::1GigabitEthernet0/0/1 [up/up] FE80::201:C9FF:FE89:4502 2001:DB8:FEED:224::1Vlan1 [administratively down/down] unassigned
R1# show ip interface briefInterface IP-Address OK? Method Status ProtocolGigabitEthernet0/0/0 192.168.10.1 YES manual up upGigabitEthernet0/0/1 209.165.200.225 YES manual up upVlan1 unassigned YES unset administratively down downR1#
Codes: L - local, C - connected, S - static, 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 i - IS-IS, su - IS-IS summary, 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, H - NHRP, l - LISP a - application route + - replicated route, % - next hop override, p - overrides from PfR
show ip route
R1# show ip routeGateway of last resort is not set 192.168.10.0/24 is variably subnetted, 2 subnets, 2 masksC 192.168.10.0/24 is directly connected, GigabitEthernet0/0/0L 192.168.10.1/32 is directly connected, GigabitEthernet0/0/0 209.165.200.0/24 is variably subnetted, 2 subnets, 2 masksC 209.165.200.224/30 is directly connected, GigabitEthernet0/0/1L 209.165.200.225/32 is directly connected, GigabitEthernet0/0/1R1#
R1 is manually configured with a static route to reach the 10.1.1.0/24 network. If this path changes, R1 will require a new static route.