Cisco IOS

Cisco Internetwork Operating System (IOS) is a family of network operating systems used on many Cisco Systems routers and current Cisco network switches

Basic commands

• show version or sh ver (includes uptime information)

Interfaces:

• show interfaces
• show interface trunk
• show interfaces switchport. To display the administrative and operational status of a switching (nonrouting) port

• show configuration or sh conf
• show running-config or sh run An enable mode command that displays the current configuration
• configure terminal or conf t Logs you into configuration mode

• show ip
• show ip interface
  • show ip interface brief or sh ip int br
• enable Logs into enable mode. Also known as user exec mode or privileged mode. See also: show privilege
  • enable 5 Change to level 5
  • no enable password

• show ip traffic
• show logging
• no shutdown. Enables an interface (brings it up).

• ip route-cache
• no ip route-cache

• ip ssh pubkey-chain

• include, similar to grep linux command

• show vlan [brief | id <vlan-id> | name <name> [ifindex] | <ifindex>]
  • show vlan
  • show vlan brief or sh vlan br
  • show vlan summary or sh vlan s

• aaa new model

• show ip route or show ip ro

• show ip arp
• show ip ssh
• show privilege

• username Create and delete users
• show users

• write

• show crypto ca certificates

Access List

Configuring IP Access Lists: https://www.cisco.com/c/en/us/support/docs/security/ios-firewall/23602-confaccesslists.html#acltypes

Types of ACLs: Standard ACLs, Extended ACLs, Lock and Key (Dynamic ACLs), IP Named ACLs, Reflexive ACLs, Time-Based ACLs Using Time Ranges, Commented IP ACL Entries, Context-Based Access Control, Authentication Proxy, Turbo ACLs, Distributed Time-Based ACLs, Receive ACLs, Infrastructure Protection ACLs, Transit ACLs.

• show access-list
• show ip access-list
• router(config)#access-list 101 deny icmp any any
• router(config)#access-list 101 permit ip any any

• router(config)#ip access-list extended test
• router(config-ext-nacl)#permit ip host 2.2.2.2 host 3.3.3.3
• router(config-ext-nacl)#permit tcp host 1.1.1.1 host 5.5.5.5 eq www
• router(config-ext-nacl)#permit icmp any any
• router(config-ext-nacl)#permit udp host 6.6.6.6 10.10.10.0 0.0.0.255 eq domain

• ip access-group

HTTP Server

• sh ip http server all
• R1(config)#ip http authentication local
• R1(config)#ip http secure-server

Configuration Guides

• Cisco IOS DHCP Server configuration
• Configure public RSA key authentication: ip ssh pubkey-chain

Activities

1. Read wikipedia article about Cisco Internetwork Operating System
2. Read Cisco IOS command reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fundamentals/command/Cisco_IOS_Configuration_Fundamentals_Command_Reference.pdf
3. Read Cisco IOS Cheat Sheet: https://www.netwrix.com/cisco_commands_cheat_sheet.html
4. Configure a user with public key access Configure public RSA key authentication
5. Associate a user with default higher privileges using username command

See also

• Cisco Networking
• Cisco Networking/CCENT/IOS Basics