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Table of Contents: Network Warrior 2nd Edition

  1. Introduction to Network Warrior
  2. Network Fundamentals
    • OSI Model and TCP/IP Stack
    • Ethernet and Switching
    • IP Addressing and Subnetting
  3. Cisco IOS Basics
    • Command Line Interface
    • Configuration Management
    • Basic Commands and Navigation
  4. Switching Technologies
    • VLANs and Trunking
    • Spanning Tree Protocol (STP)
    • EtherChannel and Link Aggregation
  5. Routing Fundamentals
    • Static Routing
    • Dynamic Routing Protocols
    • RIP, OSPF, EIGRP
  6. Advanced Routing
    • BGP (Border Gateway Protocol)
    • Route Redistribution
    • Policy-Based Routing
  7. Network Security
    • Access Control Lists (ACLs)
    • Network Address Translation (NAT)
    • VPN Technologies
  8. Quality of Service (QoS)
    • Traffic Classification
    • Queuing and Scheduling
    • Bandwidth Management
  9. Network Management
    • SNMP and Monitoring
    • Logging and Debugging
    • Performance Optimization
  10. Troubleshooting
    • Systematic Troubleshooting
    • Common Issues and Solutions
    • Tools and Techniques

1. Introduction to Network Warrior

Network Warrior by Gary A. Donahue is a comprehensive guide for network engineers working with Cisco equipment. The book focuses on practical, real-world scenarios that network professionals encounter daily.

Key Themes​

  • Practical Approach: Real-world examples and scenarios
  • Cisco-Centric: Focus on Cisco IOS and equipment
  • Troubleshooting Focus: Emphasis on problem-solving
  • Production Ready: Techniques used in live networks

2. Network Fundamentals

OSI Model and TCP/IP Stack​

The OSI (Open Systems Interconnection) model provides a framework for understanding network communication:

Layer 7: Application    - HTTP, FTP, SMTP
Layer 6: Presentation   - Encryption, Compression
Layer 5: Session        - Session Management
Layer 4: Transport      - TCP, UDP
Layer 3: Network        - IP, ICMP
Layer 2: Data Link      - Ethernet, Frame Relay
Layer 1: Physical       - Cables, Hubs

TCP/IP Stack (Simplified):

Application Layer  - HTTP, FTP, SMTP
Transport Layer    - TCP, UDP
Internet Layer     - IP, ICMP
Network Access     - Ethernet, Wi-Fi

Ethernet and Switching​

Ethernet Fundamentals​

  • CSMA/CD: Carrier Sense Multiple Access with Collision Detection
  • Frame Structure: Preamble, Destination MAC, Source MAC, Type/Length, Data, FCS
  • Speeds: 10 Mbps, 100 Mbps, 1 Gbps, 10 Gbps, 40 Gbps, 100 Gbps

Switching Concepts​

  • MAC Address Learning: Switches build MAC address tables
  • Frame Forwarding: Unicast, Broadcast, Multicast
  • Collision Domains: Each switch port is a separate collision domain
  • Broadcast Domains: VLANs create separate broadcast domains

IP Addressing and Subnetting​

IPv4 Addressing​

  • 32-bit addresses: Dotted decimal notation (192.168.1.1)
  • Classes: A (1-126), B (128-191), C (192-223), D (224-239), E (240-255)
  • Private Ranges: 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16

Subnetting​

Key Concepts:

  • Subnet Mask: Defines network and host portions
  • CIDR: Classless Inter-Domain Routing notation
  • VLSM: Variable Length Subnet Masking

Example:

Network: 192.168.1.0/24
Subnet Mask: 255.255.255.0
Hosts per subnet: 254

3. Cisco IOS Basics

Command Line Interface (CLI)​

Modes​

  1. User EXEC Mode (>)

    • Limited commands
    • Basic monitoring

  2. Privileged EXEC Mode (#)

    • Full access to show commands
    • Entered with enable

  3. Global Configuration Mode ((config)#)

    • System-wide configuration
    • Entered with configure terminal

  4. Interface Configuration Mode ((config-if)#)

    • Interface-specific configuration
    • Entered with interface <interface>

Essential Commands​

# Basic navigation
enable
configure terminal
exit
end
write memory

# Show commands
show version
show interfaces
show ip route
show running-config
show startup-config

# Interface configuration
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
no shutdown

Configuration Management​

Configuration Files​

  • Running Config: Current active configuration
  • Startup Config: Saved configuration (NVRAM)
  • Backup: Always backup configurations before changes

Best Practices​

# Save configuration
copy running-config startup-config
# or
write memory

# Backup configuration
copy running-config tftp://server/config-backup.txt

# Restore configuration
copy tftp://server/config-backup.txt running-config

4. Switching Technologies

VLANs and Trunking​

VLANs (Virtual LANs)​

Benefits:

  • Broadcast domain segmentation
  • Security isolation
  • Logical grouping of devices

Configuration:

# Create VLAN
vlan 10
name Sales

# Assign port to VLAN
interface FastEthernet0/1
switchport mode access
switchport access vlan 10

Trunking​

Trunk Protocols:

  • 802.1Q: Industry standard
  • ISL: Cisco proprietary (deprecated)

Configuration:

# Configure trunk
interface GigabitEthernet0/1
switchport mode trunk
switchport trunk allowed vlan 10,20,30

Spanning Tree Protocol (STP)​

STP Purpose​

  • Prevents loops in switched networks
  • Provides redundant path backup
  • Ensures single active path between any two network segments

STP States​

  1. Blocking: No forwarding, learns topology
  2. Listening: Participates in STP, no learning
  3. Learning: Learns MAC addresses, no forwarding
  4. Forwarding: Normal operation
  5. Disabled: Administratively disabled

STP Variants​

  • STP: Original (802.1D)
  • RSTP: Rapid STP (802.1w)
  • MSTP: Multiple STP (802.1s)

Configuration:

# Enable RSTP
spanning-tree mode rapid-pvst

# Set root bridge priority
spanning-tree vlan 10 priority 4096

EtherChannel Benefits​

  • Increased bandwidth
  • Load balancing
  • Redundancy
  • Simplified configuration

Protocols:

  • PAgP: Port Aggregation Protocol (Cisco)
  • LACP: Link Aggregation Control Protocol (IEEE 802.3ad)

Configuration:

# Configure EtherChannel
interface range GigabitEthernet0/1-2
channel-group 1 mode active

5. Routing Fundamentals

Static Routing​

Static Route Configuration​

# Basic static route
ip route 192.168.2.0 255.255.255.0 192.168.1.2

# Default route
ip route 0.0.0.0 0.0.0.0 192.168.1.1

# Floating static route (backup)
ip route 192.168.2.0 255.255.255.0 192.168.1.3 10

Static Route Advantages​

  • No routing protocol overhead
  • Predictable routing behavior
  • Security (no route advertisements)
  • Simple configuration

Dynamic Routing Protocols​

Routing Protocol Types​

  1. Distance Vector: RIP, EIGRP
  2. Link State: OSPF, IS-IS
  3. Path Vector: BGP

RIP (Routing Information Protocol)​

Characteristics:

  • Distance vector protocol
  • Hop count metric (max 15)
  • Updates every 30 seconds
  • RIPv1 (classful), RIPv2 (classless)

Configuration:

router rip
version 2
network 192.168.1.0
network 10.0.0.0
no auto-summary

OSPF (Open Shortest Path First)​

Characteristics:

  • Link state protocol
  • Cost-based metric
  • Hierarchical design (areas)
  • Fast convergence

Configuration:

router ospf 1
router-id 1.1.1.1
network 192.168.1.0 0.0.0.255 area 0
network 10.0.0.0 0.255.255.255 area 1

EIGRP (Enhanced Interior Gateway Routing Protocol)​

Characteristics:

  • Advanced distance vector
  • Composite metric (bandwidth, delay, reliability, load)
  • Fast convergence
  • Cisco proprietary

Configuration:

router eigrp 100
network 192.168.1.0
network 10.0.0.0

6. Advanced Routing

BGP (Border Gateway Protocol)​

BGP Basics​

  • Path vector protocol
  • Inter-domain routing
  • Policy-based routing
  • TCP-based (port 179)

BGP Configuration​

router bgp 65001
neighbor 192.168.1.2 remote-as 65002
network 10.0.0.0 mask 255.0.0.0

BGP Attributes​

  1. AS Path: List of AS numbers
  2. Next Hop: Next router IP
  3. Local Preference: Path preference
  4. MED: Multi-Exit Discriminator
  5. Origin: Route origin (IGP, EGP, Incomplete)

Route Redistribution​

Redistribution Concepts​

  • Metric Translation: Converting between protocols
  • Administrative Distance: Route preference
  • Route Maps: Policy control

Configuration:

router ospf 1
redistribute eigrp 100 subnets
redistribute static subnets

Policy-Based Routing (PBR)​

PBR Purpose​

  • Override normal routing
  • Traffic engineering
  • Load balancing
  • QoS routing

Configuration:

access-list 100 permit ip 192.168.1.0 0.0.0.255 any

route-map PBR permit 10
match ip address 100
set ip next-hop 192.168.2.1

interface FastEthernet0/1
ip policy route-map PBR

7. Network Security

Access Control Lists (ACLs)​

ACL Types​

  1. Standard ACLs: Source IP only
  2. Extended ACLs: Source/destination IP, protocol, port
  3. Named ACLs: Descriptive names
  4. Time-based ACLs: Time restrictions

ACL Configuration​

# Standard ACL
access-list 1 permit 192.168.1.0 0.0.0.255
access-list 1 deny any

# Extended ACL
access-list 100 permit tcp 192.168.1.0 0.0.0.255 any eq 80
access-list 100 permit tcp 192.168.1.0 0.0.0.255 any eq 443
access-list 100 deny ip any any

# Apply ACL
interface FastEthernet0/1
ip access-group 100 out

Network Address Translation (NAT)​

NAT Types​

  1. Static NAT: One-to-one mapping
  2. Dynamic NAT: Pool-based mapping
  3. PAT (NAT Overload): Many-to-one mapping

NAT Configuration​

# Static NAT
ip nat inside source static 192.168.1.10 203.0.113.10

# Dynamic NAT
ip nat pool NAT-POOL 203.0.113.10 203.0.113.20 netmask 255.255.255.0
ip nat inside source list 1 pool NAT-POOL

# PAT
ip nat inside source list 1 interface FastEthernet0/0 overload

# Define inside/outside interfaces
interface FastEthernet0/1
ip nat inside

interface FastEthernet0/0
ip nat outside

VPN Technologies​

VPN Types​

  1. Site-to-Site VPN: Router-to-router
  2. Remote Access VPN: Client-to-gateway
  3. IPSec: Security protocol suite
  4. SSL VPN: Web-based access

IPSec Configuration​

# IKE Phase 1
crypto isakmp policy 10
encryption aes 256
hash sha
authentication pre-share
group 2
lifetime 3600

# IKE Phase 2
crypto ipsec transform-set ESP-AES-SHA esp-aes esp-sha-hmac

# Crypto map
crypto map VPN-MAP 10 ipsec-isakmp
set peer 203.0.113.2
set transform-set ESP-AES-SHA
match address 100

8. Quality of Service (QoS)

QoS Concepts​

Traffic Classification​

  • Class of Service (CoS): Layer 2 marking
  • Type of Service (ToS): Layer 3 marking
  • Differentiated Services (DSCP): Modern ToS

QoS Models​

  1. Best Effort: No QoS guarantees
  2. Integrated Services (IntServ): Per-flow guarantees
  3. Differentiated Services (DiffServ): Class-based guarantees

Traffic Classification and Marking​

# Class map
class-map match-any VOICE
match dscp ef
match dscp cs3

# Policy map
policy-map QOS-POLICY
class VOICE
priority percent 30
class class-default
bandwidth remaining percent 70

# Apply policy
interface FastEthernet0/1
service-policy output QOS-POLICY

Queuing and Scheduling​

Queuing Mechanisms​

  1. FIFO: First In, First Out
  2. Priority Queuing: High priority first
  3. Custom Queuing: Bandwidth allocation
  4. Weighted Fair Queuing (WFQ): Flow-based fairness
  5. Class-Based Weighted Fair Queuing (CBWFQ): Class-based

9. Network Management

SNMP (Simple Network Management Protocol)​

SNMP Components​

  • Manager: Network management station
  • Agent: Device being managed
  • MIB: Management Information Base
  • OID: Object Identifier

SNMP Configuration​

# SNMP community
snmp-server community public RO
snmp-server community private RW

# SNMP traps
snmp-server host 192.168.1.100 public
snmp-server enable traps

Logging and Debugging​

Logging Configuration​

# Logging destination
logging host 192.168.1.100
logging facility local0
logging trap informational

# Local logging
logging buffered 4096
logging console informational

Debug Commands​

# Debug examples
debug ip ospf events
debug ip eigrp neighbors
debug ip bgp updates
debug ip nat

# Conditional debug
debug ip packet access-list 100

Performance Optimization​

Performance Monitoring​

# Interface statistics
show interfaces
show interfaces counters

# CPU and memory
show processes cpu
show memory

# Routing table
show ip route
show ip route summary

10. Troubleshooting

Systematic Troubleshooting​

Troubleshooting Methodology​

  1. Define the Problem: What exactly is wrong?
  2. Gather Information: Collect relevant data
  3. Analyze Information: Look for patterns
  4. Formulate Hypothesis: What might be causing it?
  5. Test Hypothesis: Verify your theory
  6. Implement Solution: Fix the problem
  7. Verify Solution: Ensure problem is resolved
  8. Document: Record the solution

Information Gathering​

# Basic information
show version
show running-config
show interfaces
show ip route
show arp
show mac address-table

# Detailed information
show interfaces status
show interfaces counters
show processes cpu history
show memory statistics

Common Issues and Solutions​

Connectivity Issues​

Problem: Cannot reach remote network Troubleshooting Steps:

  1. Check local connectivity (ping local gateway)
  2. Check routing table (show ip route)
  3. Check ARP table (show arp)
  4. Check interface status (show interfaces)

Performance Issues​

Problem: Slow network performance Troubleshooting Steps:

  1. Check interface utilization (show interfaces)
  2. Check for errors (show interfaces counters)
  3. Check CPU usage (show processes cpu)
  4. Check memory usage (show memory)

Security Issues​

Problem: Unauthorized access Troubleshooting Steps:

  1. Check ACLs (show access-lists)
  2. Check NAT translations (show ip nat translations)
  3. Check VPN status (show crypto isakmp sa)
  4. Review logs (show logging)

Tools and Techniques​

Built-in Tools​

# Ping with options
ping 192.168.1.1
ping 192.168.1.1 source 192.168.2.1
ping 192.168.1.1 size 1500

# Traceroute
traceroute 8.8.8.8

# Telnet/SSH
telnet 192.168.1.1
ssh -l username 192.168.1.1

External Tools​

  • Wireshark: Packet analysis
  • Nmap: Network scanning
  • SolarWinds: Network monitoring
  • PRTG: Network monitoring
  • Cacti: SNMP monitoring

11. Best Practices

Configuration Management​

  1. Document Everything: Keep detailed records
  2. Backup Configurations: Regular backups
  3. Change Management: Formal change process
  4. Testing: Test changes in lab first
  5. Rollback Plans: Always have a rollback strategy

Security Best Practices​

  1. Strong Passwords: Use complex passwords
  2. Access Control: Limit administrative access
  3. Regular Updates: Keep IOS updated
  4. Monitoring: Monitor for security events
  5. Documentation: Document security policies

Performance Best Practices​

  1. Baseline Performance: Establish baselines
  2. Regular Monitoring: Continuous monitoring
  3. Capacity Planning: Plan for growth
  4. Optimization: Regular optimization
  5. Documentation: Document performance metrics

12. Use Cases

When to use Network Warrior concepts:

  • Enterprise network design and implementation
  • Cisco equipment configuration and management
  • Network troubleshooting and optimization
  • Security policy implementation
  • Performance monitoring and tuning
  • Disaster recovery planning

Key scenarios covered:

  • Multi-site network connectivity
  • VLAN design and implementation
  • Routing protocol selection and configuration
  • Security policy enforcement
  • QoS implementation for voice/video
  • Network monitoring and management

13. References