Basic CISCO commands and tips from Netskills youtube course Young Fighter’s Course

Basics

enable #enable privileged conf t #configure global ? #help sh run #show running configuration sh vlan #show vlan configuration sh mac address-table #show all macs from switch db do sh #show something from conf t mode write mem #save conf

Authorization and User management

Enable login via password in console
enable conf t enable password new_pass
Encrypted password
enable conf t service password-encryption

Secret (More prioritized than password)
enable conf t enable secret new_secret

Create user
enable conf t username NEW_USER privilege <0-15> NEW_PASSWORD

Enable local authorization
enable conf t line console 0 login local

Interface configuraion / VLAN’s

Configure IP on switch port for telnet access
enable conf t interface Vlan1 ip address 192.168.1.1 255.255.255.0 no shutdown exit line vty 0 4 transport input telnet login local end write mem

Vlan

VLAN - ensure security in our infrastructure and give us an ability to make 4095 identical subnets with different VLAN’s tags without any broadcast noise.
Working on the second level of the OSI model.
Two different port modes on switch’s:

• Access ports (for end-users like computers)
• Trunk ports (for other switches)
  Configuration:
  enable conf t interface vlan 2 name group_1 exit interface FastEthernet 0/1 switchport mode access switchport access vlan 2 exit interface GigabyteEhternet 0/1 switchport mode trunk switchport trunk allowed vlan 2 switchport trunk allowed vlan add 3 exit

STP

STP - spanning tree protocol. Protects us from loops in our network and reduces broadcast traffic.
How it works

1. Connected switches begin to initialize connected ports (every 2 sec BPDU frames are send)
2. Switch with highest throughput elected as root swith in topology
3. If all switches are identical in throughput then the switch with an lowest MAC address would be elected as a root
4. On the next step root ports on non-root switches will be determined (same algorithm - lowest mac on highest throughput)
5. Determination of the designate port on non-root switch (this port will be used for connection with blocked port from next step)
6. Block of the port on another non-root switch
   So with topology which consists from three switches we have this picture:
   First Switch with the lowest MAC will be elected as a root switch with two ports in forwarding mode Second switch with average MAC will be used as non-root switch with both ports in forwarding mode (one of them will be root port connected with root switch and aonther will be a designated port connected with a blocked port on the third switch)
   The last one switch with highest MAC ( or lowest throughput) will be determined as a non-root switch with one root port connected with root switch and another one blocked

Commands:
spanning-tree spanning-tree vlan X priority spanning-tree vlan X primary spanning-tree vlan mode rapid-pvst