updated summary page and added cli examples

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Hugh Ratsch
2025-01-29 16:33:31 -06:00
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# Cisco IOS Command Reference Sheet
## Basic Device Access
```cisco
# Access Modes
enable # Privileged EXEC Mode (User → Privileged)
configure terminal # Global Configuration Mode (Privileged → Global)
end # Return to Privileged EXEC Mode
exit # Exit one level back
# Basic Show Commands
show running-config # Current configuration
show startup-config # Saved configuration
show version # IOS version and hardware info
show flash: # Contents of flash memory
show history # Previously used commands
# Configuration Management
write memory # Save configuration
copy running-config startup-config # Save configuration (alternative)
erase startup-config # Erase saved configuration
reload # Restart device
```
## Device Configuration
```cisco
# System Settings
hostname DEVICE_NAME
service password-encryption # Encrypt plaintext passwords
no ip domain-lookup # Disable DNS lookup
banner motd #MESSAGE# # Set login banner
# Password Configuration
enable secret PASSWORD # Encrypted privileged mode password
enable password PASSWORD # Plaintext privileged mode password
# Console Settings
line console 0
password PASSWORD
login
logging synchronous # Prevent command interruption by logs
# SSH Configuration
ip domain-name DOMAIN
crypto key generate rsa modulus 2048
username ADMIN privilege 15 secret PASSWORD
line vty 0 15
transport input ssh
login local
```
## Interface Configuration
```cisco
# Basic Interface Commands
interface GigabitEthernet0/0
description LINK_DESCRIPTION
ip address 192.168.1.1 255.255.255.0
no shutdown
duplex {auto|full|half}
speed {auto|10|100|1000}
mtu 1500
# Interface Status Commands
show ip interface brief # Quick interface status
show interfaces # Detailed interface statistics
show interfaces description # Interface descriptions
show interfaces status # L1/L2 interface status
show controllers # Interface hardware status
# Interface Range Configuration
interface range g0/0 - 3 # Configure multiple interfaces
interface range g0/0, g0/2 # Select specific interfaces
default interface g0/0 # Reset interface configuration
```
## Layer 2 Switching
```cisco
# VLAN Configuration
vlan 10
name DEPARTMENT
show vlan brief
show vlan id 10
# Access Port Configuration
interface g0/1
switchport mode access
switchport access vlan 10
switchport port-security
switchport port-security maximum 2
switchport port-security mac-address sticky
# Trunk Configuration
interface g0/1
switchport mode trunk
switchport trunk allowed vlan 10,20,30
switchport trunk native vlan 999
switchport nonegotiate # Disable DTP
# VTP Configuration
vtp mode {server|client|transparent}
vtp domain DOMAIN_NAME
vtp version {1|2|3}
show vtp status
```
## Spanning Tree Protocol
```cisco
# Global STP Commands
spanning-tree mode {pvst|rapid-pvst|mst}
spanning-tree extend system-id
show spanning-tree
show spanning-tree summary
# VLAN STP Configuration
spanning-tree vlan 1 root primary
spanning-tree vlan 1 root secondary
spanning-tree vlan 1 priority 24576
# Interface STP Configuration
interface g0/1
spanning-tree portfast
spanning-tree bpduguard enable
spanning-tree guard root
spanning-tree cost 100
spanning-tree port-priority 64
```
## EtherChannel
```cisco
# LACP Configuration
interface range g0/1-2
channel-group 1 mode active # LACP active
channel-group 1 mode passive # LACP passive
# PAgP Configuration
interface range g0/1-2
channel-group 1 mode desirable # PAgP desirable
channel-group 1 mode auto # PAgP auto
# Static Configuration
interface range g0/1-2
channel-group 1 mode on # Force channel without protocol
# Verification Commands
show etherchannel summary
show etherchannel port-channel
show etherchannel load-balance
```
## Layer 3 Routing
```cisco
# Basic Routing Commands
ip routing # Enable routing on L3 switch
show ip route
show ip protocols
# Static Routes
ip route 0.0.0.0 0.0.0.0 NEXT_HOP # Default route
ip route NETWORK MASK NEXT_HOP # Static route
ip route NETWORK MASK Null0 # Null route
# OSPF Configuration
router ospf 1
router-id 1.1.1.1
network 192.168.1.0 0.0.0.255 area 0
default-information originate
passive-interface default
no passive-interface g0/1
interface g0/1
ip ospf 1 area 0
ip ospf cost 100
ip ospf priority 255
```
## NAT & PAT
```cisco
# Static NAT
ip nat inside source static LOCAL_IP GLOBAL_IP
# Dynamic NAT
ip nat pool NAT_POOL 200.1.1.1 200.1.1.10 netmask 255.255.255.0
ip nat inside source list 1 pool NAT_POOL
# PAT (NAT Overload)
access-list 1 permit 192.168.1.0 0.0.0.255
ip nat inside source list 1 interface g0/1 overload
# NAT Interface Configuration
interface g0/0
ip nat inside
interface g0/1
ip nat outside
# Verification
show ip nat translations
show ip nat statistics
```
## Network Services
```cisco
# DHCP Server
ip dhcp excluded-address 192.168.1.1 192.168.1.10
ip dhcp pool POOL_NAME
network 192.168.1.0 255.255.255.0
default-router 192.168.1.1
dns-server 8.8.8.8
lease 7
# DHCP Relay
interface g0/1
ip helper-address DHCP_SERVER_IP
# NTP Configuration
ntp server IP_ADDRESS
ntp master
ntp authenticate
ntp trusted-key 1
ntp authentication-key 1 md5 PASSWORD
# Syslog
logging host IP_ADDRESS
logging trap debugging
logging facility local7
```
## Monitoring & Troubleshooting
```cisco
# Discovery Protocols
show cdp neighbors detail
show lldp neighbors detail
show cdp interface
# Debug Commands
debug ip ospf packet
debug ip ospf hello
no debug all # Disable all debugging
# Interface Diagnostics
show interfaces counters
show interfaces counters errors
show controllers ethernet-controller
show processes cpu
show memory statistics
# Logging
show logging
show logging history
terminal monitor # Enable logging in SSH/Telnet
```
---
## 1. Basic Device Configuration
### 1.1 Initial Device Access
- **Enable Mode**: Access privileged EXEC mode
```cisco
Router> enable
Router#
```
- **Configuration Mode**: Enter global configuration mode
```cisco
Router# configure terminal
Router(config)#
```
- **Basic Device Security**:
```cisco
enable password boson # Basic password (not encrypted)
enable secret boson # Encrypted password (preferred)
```
### 1.2 Device Management
- **Hostname Configuration**:
```cisco
hostname R1
```
- **Interface Configuration**:
```cisco
interface GigabitEthernet 0/0
description Connection to SW1
ip address 192.168.1.1 255.255.255.0
no shutdown
```
- **Saving Configuration**:
```cisco
write memory # or 'wr'
copy running-config startup-config
```
## 2. Interface Configuration
### 2.1 IPv4 Configuration
```cisco
## conf ipv4 ##
en
conf t
int f0/1
ip addr 192.168.1.1 255.255.255.0
no shut
end
wr
```
- Purpose: Configures basic IPv4 addressing on an interface
- Key Components:
- `ip addr`: Assigns IP address and subnet mask
- `no shut`: Enables the interface
- `wr`: Saves configuration to NVRAM
### 2.2 IPv6 Configuration
```cisco
## conf ipv6 ##
en
conf t
ipv6 unicast-routing
int f0/1
ipv6 addr 2001:db8:3445:abde::1/64
no shut
end wr
```
- Purpose: Enables and configures IPv6 on an interface
- Key Components:
- `ipv6 unicast-routing`: Enables IPv6 routing globally
- `ipv6 addr`: Assigns IPv6 address with prefix length
## 3. VLAN Configuration
### 3.1 Basic VLAN Setup
```cisco
## create vlan and conf name ##
en
conf t
vlan 10
name Sales
## conf int as switchport for vlan ##
int f0/1
sw mo ac
switchport access vlan 10
```
- Purpose: Creates and assigns VLANs to interfaces
- Key Concepts:
- VLANs segment broadcast domains
- Access ports belong to single VLAN
- Trunk ports carry multiple VLAN traffic
### 3.2 VLAN Trunking
```cisco
## conf SW for 802.1q and trunking mode ##
en
conf t
int f0/1
sw tr enc dot1q
sw mo tr
```
- Purpose: Configures trunk links between switches
- Features:
- 802.1Q tagging for VLAN identification
- Supports multiple VLANs over single link
- Can specify allowed VLANs
### 3.3 Inter-VLAN Routing
```cisco
## create a subint for vlan 10 ##
en
conf t
int f0/0.10
enc dot1q 10
ip addr 192.168.10.1 255.255.255.192
```
- Purpose: Enables routing between VLANs
- Methods:
- Router-on-a-stick (shown above)
- Layer 3 switch routing
- Multiple physical interfaces
## 4. Spanning Tree Protocol (STP)
### 4.1 Basic STP Configuration
```cisco
## conf vlan pvst (Rapid-PVST+) ##
en
conf t
spanning-tree vlan 100 priority root
## conf portfast on int f0/1 ##
int f0/1
spanning-tree portfast
```
- Purpose: Prevents layer 2 loops
- Key Features:
- Root bridge election
- Loop prevention
- Convergence optimization
## 5. EtherChannel Configuration
### 5.1 Layer 2 EtherChannel
```cisco
## layer 2 etherchannel ##
en
conf t
int r f0/1 - 4
channel-group 1 mode active
```
- Purpose: Combines multiple physical links into one logical link
- Benefits:
- Increased bandwidth
- Redundancy
- Load balancing
## 6. Security Features
### 6.1 SSH Configuration
```cisco
## conf ssh ##
en
conf t
line vty 0 15
no password sharedpassword
login local
transport input ssh # enable ssh only
## ssh generate rsa key ##
crypto key generate rsa
```
- Purpose: Secure remote access
- Key Components:
- RSA key generation
- VTY line configuration
- Authentication methods
### 6.2 Port Security
```cisco
## Basic Port Security ##
en
conf t
int f0/1
switchport port-security
switchport port-security maximum 2
switchport port-security mac-address sticky
```
- Purpose: Prevents unauthorized access at switch ports
- Features:
- MAC address limiting
- Violation actions
- Sticky learning
## 7. Routing Protocols
### 7.1 OSPF Configuration
```cisco
## conf OSPF process and area on int ##
en
conf t
int f0/1
ip ospf 10 area 0
## conf network to operate in OSPF area 0 ##
router ospf 10
network 203.0.113.0 0.0.0.7 area 0
```
- Purpose: Dynamic routing protocol for internal networks
- Key Concepts:
- Area-based hierarchy
- Link-state protocol
- Dijkstra's algorithm for path selection
- Verification Commands:
```cisco
show ip ospf
show ip ospf neighbor
show ip route ospf
```
### 7.2 Static Routing
```cisco
## conf a default route by int ##
ip route 0.0.0.0 0.0.0.0 int f0/1
## conf a default route by next int ip addr ##
ip route 0.0.0.0 0.0.0.0 203.0.113.1
```
- Purpose: Manually configured routes
- Use Cases:
- Default routes
- Stub networks
- Small network designs
## 8. Network Address Translation (NAT)
### 8.1 Static NAT
```cisco
## implement static nat on router ##
en
conf t
int g0/0
ip nat outside
int g0/1
ip nat inside
exit
ip nat inside source static 192.168.100.38 192.0.2.9
```
- Purpose: One-to-one mapping of private to public addresses
- Verification:
```cisco
show ip nat translations
show ip nat statistics
```
### 8.2 PAT (NAT Overload)
```cisco
## conf pat aka nat overload ##
en
conf t
access-list 1 permit 192.168.100.32 0.0.0.31
int g0/1
ip nat inside
int g0/0
ip nat outside
ip nat inside source list 1 interface g0/0 overload
```
- Purpose: Many-to-one address translation
- Benefits:
- Conserves public IP addresses
- Common in home/small business networks
## 9. Network Services
### 9.1 DHCP Configuration
```cisco
## conf dhcp server ##
en
conf t
service dhcp
ip dhcp excluded-address 172.16.10.17
ip dhcp pool pool_one
network 172.16.10.16 255.255.255.240
default-router 172.16.10.17
## conf dhcp relay ##
int f0/1
ip helper 203.0.113.1
```
- Purpose: Automatic IP address assignment
- Components:
- DHCP pool definition
- Excluded addresses
- Default gateway
- DHCP relay for remote networks
### 9.2 NTP Configuration
```cisco
## conf ntp server ##
en
conf t
ntp master
## conf ntp client ##
ntp authenticate
ntp authentication-key 1 md5 80$0n!
ntp trusted-key 1
ntp server 203.0.113.5 key 1
```
- Purpose: Network time synchronization
- Security Features:
- Authentication
- Access control lists
- Trusted keys
### 9.3 DNS Configuration
```cisco
## enable dns server ##
en
conf t
ip dns server
## conf dns host table ##
ip host www 192.168.52.44
```
- Purpose: Domain name resolution
- Features:
- Local DNS server
- Static host mappings
- DNS forwarding
## 10. High Availability
### 10.1 HSRP Configuration
```cisco
## conf hsrp ##
en
conf t
int f0/0
standby 1 ip 192.168.1.1
standby 1 priority 110
standby 1 preempt
```
- Purpose: Router redundancy protocol
- Features:
- Virtual IP address
- Priority-based active router selection
- Preemption capability
### 10.2 VRRP Configuration
```cisco
## conf vrrp ##
en
conf t
int vlan 100
vrrp 1 ip 192.168.100.1
vrrp 1 priority 110
```
- Purpose: Alternative to HSRP
- Key Differences:
- Industry standard (vs. Cisco proprietary HSRP)
- Similar functionality
## 11. Troubleshooting
### 11.1 Interface Status
```cisco
## check all int ##
show ip interface brief
show interface status # switches only
## check one int ##
show ip interface f0/1
```
- Purpose: Verify interface operation
- Key Information:
- Line/protocol status
- IP addressing
- Interface errors
### 11.2 Protocol Debugging
```cisco
## debug ospf hello msg ##
debug ip ospf hello
## show nat translations ##
show ip nat translations
## show routing table ##
show ip route
```
- Purpose: Detailed protocol analysis
- Best Practices:
- Use specific debug commands
- Monitor system resources
- Clear debug when finished
### 11.3 Common Show Commands
```cisco
show running-config
show vlan brief
show spanning-tree
show etherchannel summary
show cdp neighbors
```
- Purpose: Configuration verification
- Use Cases:
- Troubleshooting
- Documentation
- Change verification
## 12. Best Practices
### 12.1 Configuration Management
- Save configurations regularly
- Document changes
- Use consistent naming conventions
- Implement secure passwords
- Regular backups
### 12.2 Security Guidelines
- Disable unused ports
- Use secure protocols (SSH vs Telnet)
- Implement access lists
- Regular security audits
- Password best practices
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- [Dynamic Routing](3-ip-connectivity.md#dynamic-routing) - [Dynamic Routing](3-ip-connectivity.md#dynamic-routing)
- [IP Services](4-ip-services.md) - [IP Services](4-ip-services.md)
- [Security Fundamentals](5-security-fundamentals.md) - [Security Fundamentals](5-security-fundamentals.md)
- [Automation and Programmability](6-automation-and-programmability.md) - [Automation and Programmability](6-automation-and-programmability.md)
- [Command Line Examples](7-command-line-examples.md)