Information Technology | Basic Cisco Switch and Router Configuration

Basic Cisco Switch and Router Configuration

29 Apr 2023

Networking

Switch Configuration

1) Enter privilege mode :

Switch> enable

Switch> en

2) Enter global configuration mode :

Switch# configure terminal

Switch# config term

3) Disables the switch from translating unfamiliar words (typos) into IP addresses :

Switch(config)# no ip domain-lookup

4) Specifies the name for the switch :

Switch(config)# hostname <switch's name>

5) Set a password that is required for any user to enter global configuration mode :

Switch(config)# enable secret <password>

6) Set a password for the console port of the switch and enables password verification at the terminal login session :

Line con 0 refers to the console port of the switch (it is usually either an RJ-45 or, on newer devices, a USB port). The console port is used to physically connect (a PC or laptop) to the device.
```
Switch(config)# line con 0
Switch(config-line)# password <password>
Switch(config-line)# login
```

7) Set a password for VTY (Virtual Terminal) and enables password verification at the virtual terminal login session :

The virtual terminal, or “VTY” lines are virtual lines that allow connecting to the device using telnet or Secure Shell (SSH). Cisco devices can have up to 16 VTY lines. You can determine how many VTY lines you have by issuing “line vty 0 ?” from global configuration mode. The value 0 4 in this command means “from virtual terminal 0 to virtual terminal 4” because in this situation we assume that this switch can have only 5 users login to a virtual terminal (telnet or SSH) at the same time. The device can allow 5 simultaneous virtual connections. By default five vty lines (0–4) are open.
```
Switch(config)# line vty 0 4
Switch(config-line)# password <password>
Switch(config-line)# login
```

8) Encrypt the password :

This command obscures all clear-text passwords in the configuration using a Vigenere cipher.
```
Switch(config)# service password-encryption
```

9) Set a login banner, known as the message of the day (MOTD) banner :

Switch(config)# banner motd #

10) Save the configuration :

This command saves the running configuration to the startup file on non-volatile random access memory (NVRAM).
```
Switch# copy running-config startup-config
```
OR
```
Switch(config)# wr
```

11) List all the IP interfaces or physical port and VLAN in the switch :

This command shows the type (Fast Ethernet, Gigabit Ethernet, VLAN), IP address, status, and protocol of the interface.
```
Switch# show ip interface brief
```
OR
```
Switch# sh ip int brief
```

12) Enter the interface configuration mode for the specific VLAN ID, assign an IP address to that VLAN and brings up the interface :

In Switch, an IP address will only be assigned to the Switch Virtual Interface (VLAN interface) when we want to use Layer 3 routing (IP routing), such as interVLAN routing and management VLAN.
Switch Virtual Interface or SVI is a virtual routed interface or logical routed interface that represents all of the ports belonging to that VLAN.
An IP address is assigned to the VLAN interface. An IP address can’t be assigned to an interface port. By default, all interface ports is in VLAN 1 (Native VLAN by default).
There are differences between a switch port and routed port. A routed port is a physical port that can route IP traffic (Layer 3/Network Layer) to another device.
This command shows an example of creating a VLAN interaface using the “int vlan” command and assigning an IP address to the interface VLAN 1.
The no shutdown command will bring the interface “up”, while the shutdown command will shut down the interface, and the status of the interface will be “administratively down”.
```
Switch(config)# int vlan 1
Switch(config-if)# ip address <ip-address> <subnet-mask>
Switch(config-if)# no shutdown
```

13) Configure the IP default gateway for the switch :

The default gateway is the address of the interface port (Router) that is connecting directly to the switch.
The default gateway must be configured on a layer 2 switch to allow traffic to be sent to a remote network or remote subnet (different network or different subnet).
If the default gateway is not configured, any traffic that is receive on the switch would not be able to be sent again to source address (Sender would not get any reply from the switch).
Layer 2 switches are different from layer 3 switches (multilayer switch). layer 3 switches have an IP routing feature that allows traffic to be sent to other networks (layer 3 IP routing).
In layer 3 switch (Multilayer Switch), we don’t need a default gateway, we just need to enable IP routing feature.
If the Layer 2 switch is directly connected to the Multilayer Switch, the default gateway is only used when the IP routing feature on Multilayer Switch is disabled. Otherwise, we need to use the IP default route on the Layer 2 switch when the IP routing feature is enabled. Reference
```
Switch(config)# ip default-gateway 192.168.1.1
```

14) Enabling port security on the switch :

Port Security limits the number of valid MAC addresses allowed to transmit data through a switch port (If an unknown MAC address sends data through the port, it will be dropped by the switch and take an action based on Violation Modes - Default Mode: Shutdown).

Before enabling port security, the port must be configured as a static port, whether access or trunk.

Switch(config)# int FastEthernet 0/1
Switch(config)# switchport mode access
Switch(config)# switchport port-security

Router Configuration

1) Enter privilege mode :

Router> enable

Router> en

2) Enter global configuration mode :

Router# configure terminal

Router# config term

3) Disables the router from translating unfamiliar words (typos) into IP addresses :

Router(config)# no ip domain-lookup

4) Specifies the name for the router :

Router(config)# hostname <router's name>

5) Set a password that is required for any user to enter global configuration mode :

Router(config)# enable secret <password>

6) Set a password for the console port of the router and enables password verification at the terminal login session :

Line con 0 refers to the console port of the router (it is usually either an RJ-45 or, on newer devices, a USB port). The console port is used to physically connect (a PC or laptop) to the device.
```
Router(config)# line con 0
Router(config-line)# password <password>
Router(config-line)# login
```

7) Set a password for VTY (Virtual Terminal) and enables password verification at the virtual terminal login session :

The virtual terminal, or “VTY” lines are virtual lines that allow connecting to the device using telnet or Secure Shell (SSH). Cisco devices can have up to 16 VTY lines. You can determine how many VTY lines you have by issuing “line vty 0 ?” from global configuration mode. The value 0 4 in this command means “from virtual terminal 0 to virtual terminal 4” because in this situation we assume that this router can have only 5 users login to a virtual terminal (telnet or SSH) at the same time. The device can allow 5 simultaneous virtual connections. By default five vty lines (0–4) are open.
```
Router(config)# line vty 0 4
Router(config-line)# password <password>
Router(config-line)# login
```

8) Encrypt the password :

This command obscures all clear-text passwords in the configuration using a Vigenere cipher.
```
Router(config)# service password-encryption
```

9) Set a login banner, known as the message of the day (MOTD) banner :

Router(config)# banner motd #

10) Save the configuration :

This command saves the running configuration to the startup file on non-volatile random access memory (NVRAM).
```
Router# copy running-config startup-config
```
OR
```
Router(config)# wr
```

11) List all the IP interfaces or physical port of the router :

This command shows the type (Fast Ethernet, Gigabit Ethernet, Subinterface, VLAN), IP address, status, and protocol of the interface.
```
Router# show ip interface brief
```
OR
```
Router# sh ip int brief
```

12) Enter the interface configuration mode for the specific interface port and assign an IP address to that interface port :

This command shows an example of assigning an IP address to the interface FastEthernet 0/1.
The no shutdown command will bring the interface “up”, while the shutdown command will shut down the interface, and the status of the interface will be “administratively down”.
```
Router(config)# int FastEthernet 0/1
Router(config-if)# ip address <ip-address> <subnet-mask>
Router(config-if)# no shutdown
```

13) Adding a description to an interface configuration :

This command shows an example of assigning an IP address to the interface GigabitEthernet 0/1.
The description command is meant to provide a reminder in the configuration to describe what certain interfaces are used for.
```
Router-1(config)# int GigabitEthernet 0/1
Router-1(config-if)# description Link Directly Connected to Router-2
```

Basic Cisco Switch and Router Configuration

Switch Configuration

Router Configuration

Reference :