IP Routing on Cisco IOS, IOS XE, and IOS XR: An Essential Guide to Understanding and Implementing IP Routing Protocols

About This eBook
Title Page
Copyright Page
About the Authors
About the Technical Reviewers
Dedications
Acknowledgments
Contents at a Glance
Contents
Icons Used in This Book
Command Syntax Conventions
Foreword
Introduction
Who Should Read This Book?
How This Book Is Organized
Final Words
Part I: Network Fundamentals
Chapter 1. Introduction to the Operating Systems
IOS, IOS XE, and IOS XR Software Architecture
IOS
Kernel and OS Scheduling
Memory Management
Software Packaging
IOS XE
Kernel and OS Scheduling
Memory Management
IOS XR
Kernel and OS Scheduling
Memory Management
Software Packaging
Debugging
CLI and Configuration
IOS
User Mode
Privileged Mode
Global Configuration Mode
Configuration Archiving
Configuration Replace
IOS XR
Viewing Changes in the SysDB
Commit Label
Commit Replace
Failed Commits
Configuration Rollback
Commit Confirmed
Multiple Commit Options
Loading Files for Changes
Hierarchical Configuration
PWD
Root
Summary
References in This Chapter
Chapter 2. IPv4 Addressing
IP Fundamentals
Understanding Binary
Address Classes
Subnet Masks and Subnetting
Subnet Mask Purpose
Calculating Usable IP Addresses
Network Prefix Notation
Subnetting
Subnet Field
Subnet Math
Subnet Design
Classless Interdomain Routing
Classful Versus Classless Routing
Classful Routing
Classless Routing
Variable-Length Subnet Masks
Summarization
Private IP Addressing
Special IP Addresses
IPv4 Address Configuration
Wildcard Subnet Masks
Summary
References in This Chapter
Chapter 3. How a Router Works
IP Routing
Distance Vector Algorithms
Enhanced Distance Vector Algorithm
Link-State Algorithms
Path Vector Algorithm
Routing Table
Prefix Length
Administrative Distance
Metrics
Virtual Routing and Forwarding
IP Packet Switching
Process Switching
Cisco Express Forwarding
Software CEF
Hardware CEF
Planes of Operation
Summary
References in This Chapter
Part II: Routing Protocols
Chapter 4. Static Routing
Connected Networks
Secondary Connected Networks
Static Routing Fundamentals
Point-to-Point Interfaces
Broadcast Interfaces
Default Route
Floating Static Routing
Recursive Lookup
Multihop Routing
Single Recursive Lookup
Multiple Recursive Lookups
Problems with Static Route Recursion
Null Interface
Static VRF Routes
Summary
References in This Chapter
Chapter 5. EIGRP
EIGRP Fundamentals
EIGRP Neighbors
Inter-Router Communication
Forming EIGRP Neighbors
Classic EIGRP Autonomous System Configuration
IOS network Statement
IOS XR
Passive Interfaces
Sample Topology and Configuration
Confirmation of Interfaces
Verification of EIGRP Neighbor Adjacencies
Display of Installed EIGRP Routes
Router ID
EIGRP Terminology
Topology Table
Path Metric Calculation
Custom K Values
Interface Delay Settings
Load Balancing
EIGRP Wide Metrics
Failure Detection and Timers
Convergence
Stuck in Active
Stub
Design Considerations with EIGRP Stubs
Summarization
Interface-Specific Summarization
Summarization Metrics
Advertising a Default Route
Automatic Summarization
Authentication
Enabling Authentication on the interface
Key Chain Configuration
WAN Considerations
IP Bandwidth Percent
Split Horizon
Next-Hop Self
EIGRP Named Configuration
Address Family Instance Configuration
Address Family Interface Configuration
Address Family Topology Configuration
Summary
References in This Chapter
Chapter 6. OSPF
OSPF Fundamentals
Inter-Router Communication
OSPF Hello Packets
Router ID
Neighbors
Forming OSPF Neighbor Adjacencies
Basic OSPF Configuration
IOS network Statement
IOS Interface Specific
IOS XR
Passive Interfaces
Sample Topology and Configuration
Confirmation of Interfaces
Verification of OSPF Neighbor Adjacencies
Verification of OSPF Routes
Designated Router and Backup Designated Router
Designated Router Elections
DR and BDR Placement
Failure Detection
Hello Timer
Dead Interval Timer
Verifying OSPF Timers
OSPF Fast Packet Hellos
OSPF Network Types
Broadcast
Non-Broadcast
Point-to-Point Networks
Point-to-Multipoint Networks
Loopback Networks
Review of OSPF Network Types
OSPF Adjacency with Different OSPF Network Types
Link Costs
Authentication
IOS Support for OSPF Authentication
IOS XR Support for OSPF Authentication
Summary
References in This Chapter
Chapter 7. Advanced OSPF
Areas
Area ID
OSPF Route Types
External OSPF Routes
Link-State Announcements
LSA Age and Flooding
LSA Types
LSA Type 1: Router Link
LSA Type 2: Network Link
LSA Type 3: Summary Link
LSA Type 5: External Routes
LSA Type 4: ASBR Summary
LSA Type 7: NSSA External Summary
LSA Type Summary
OSPF Path Selection
Intra-Area Routes
Interarea Routes
External Route Selection
E1 and N1 External Routes
E2 and N2 External Routes
Equal Cost Multi-Path
Summarization of Routes
Interarea Summarization
External Summarization
Default Route
OSPF Stubby Areas
Stub Areas
Totally Stubby Areas
Not-So-Stubby Areas
Totally NSSA Areas
Virtual Links
Discontiguous Network
Multi-Area Adjacency
Prefix Suppression
Summary
References in This Chapter
Chapter 8. IS-IS
IS-IS Fundamentals
Areas
OSI Addressing
Inter-Domain Part
Domain Specific Part
NET Addressing
Inter-Router Communication
IS Protocol Header
TLVs
IS PDU Addressing
Hello Packets
Link-State Packets
LSP Lifetime
LSP ID
LSP Sequence
Attribute Fields
LSP Packet and TLVs
IS-IS Neighbor
Ethernet
Point-to-Point
Basic IS-IS Configuration
IOS
IOS XR
Sample Topology and Configuration
Confirmation of IS-IS Interfaces
Verification of IS-IS Neighbor Adjacencies
Verification of IS-IS Routes
Designated Intermediate System
DIS Elections
DIS Placement
Point-to-Point Adjacency on Broadcast Media
Link State Packet Database
Viewing the LSPDB
Non-Pseudonode LSPs
Pseudonode LSPs
Building the Topology
Viewing the Topology
SPF Calculations
Passive Interfaces
Removal of Hello Padding
Failure Detection
Hello Timer
Hello Multiplier and Holding Timer
Authentication
IS-IS Hello Authentication
IS-IS LSP Authentication
Summary
References in This Chapter
Chapter 9. Advanced IS-IS
Advanced IS-IS Routing
Route Leaking
Backbone Continuity
Loop Prevention
Router-Specific IS-IS Levels
Interface Specific IS-IS Levels
Path Selection
Equal Cost Multi-Path
Interface Metrics
Overload Bit
Summarization
Default Routes
Prefix Suppression
Summary
References in This Chapter
Chapter 10. Border Gateway Protocol
BGP Fundamentals
Autonomous System Numbers
Path Attributes
Loop Prevention
Address Families
Inter-Router Communication
Open Messages
Hold Time
BGP Identifier
Keepalive Messages
Update Messages
Notification Messages
BGP Sessions
BGP Neighbor States
Idle State
Connect State
Active State
OpenSent State
OpenConfirm State
Established State
Basic BGP Configuration
IOS
IOS XR
Verification of BGP Sessions
Prefix Advertisement
Receiving and Viewing Routes
iBGP
iBGP Full-Mesh Requirement
Peering via Loopback Addresses
eBGP
eBGP and iBGP Topologies
Next-Hop Manipulation
iBGP Scalability
Route Reflectors
Loop Prevention in Route Reflectors
Out-of-Band Route Reflectors
Confederations
Failure Detection
Security
eBGP Multihop
TTL Security
Summary
References in This Chapter
Part III: Advanced Routing Techniques
Chapter 11. Route Maps and Route Policy
Access Control Lists
Standard ACLs
Extended ACLs
IGP Network Selection
BGP Network Selection
Prefix Matching
Prefix Lists
Prefix Sets
Regular Expressions
_
^
$
[ ]
-
[^]

.
+
?
*
Looking Glass and Route Servers
AS_Path Access List
IOS XR AS_Path Selection Options
is-local
length
unique-length
passes-through
neighbor-is
originates-from
AS Path Set
Route Maps
Conditional Matching
Multiple Conditional Match Conditions
Complex Matching
Optional Actions
Continue
Route Map Examples
Routing Policy Language
Route Policy Structure
Match Statements
Attribute Modification
Common Route Policy Structure
Boolean Operators
Negation
Conjunction
Disjunction
Order of Processing
Comparing Prefix Sets to Prefix Lists
Parameterization
Route Policy Nesting
Original Value
Editors
RPL Examples
RPL Verification
Redistribution RPL Verification
BGP RPL Verification
Summary
References in This Chapter
Chapter 12. Advanced Route Manipulation
Conditional Routing of Packets
Policy-Based Routing Configuration
Access-List-Based Forwarding Configuration
Local PBR
Administrative Distance
Modifying EIGRP AD
Modifying OSPF AD
Modifying IS-IS AD
Modifying BGP AD
Route Filtering and Manipulation
EIGRP Filtering by Prefix
EIGRP Filtering by Hop Count
EIGRP Offset Lists
OSPF Filtering
OSPF Filtering
IS-IS Filtering
BGP Filtering
Clearing BGP Connections
Summary
References in This Chapter
Chapter 13. Route Redistribution
Redistribution Basics
Redistribution Is Not Transitive
Sequential Protocol Redistribution
Routes Must Exist in the RIB
Metrics
Protocol-Specific Configuration
Source-Specific Behaviors
Connected Networks
IS-IS
BGP
Destination-Specific Behaviors
EIGRP
OSPF
IS-IS
BGP
Challenges with Redistribution
Route Feedback
Suboptimal Routing
Invalid Routing Tables
Routing Loops
Methods to Avoid Routing Loops
Prefix Filtering
Tagging
Increase Seed Metrics
Administrative Distance
Summarization on Redistributing Router
Solutions to Redistribution Challenges
Summary
References in This Chapter
Part IV: Advanced BGP
Chapter 14. Advanced BGP
BGP Communities
Enabling BGP Community Support
Well-Known Communities
Internet
No_Export
No_Advertise
No_Export_SubConfed
Conditionally Matching BGP Communities
Community Set
Inline
Setting Private BGP Communities
Route Summarization
Aggregate Address
Flexible Route Suppression
Selective Prefix Suppression
Leaking Suppressed Routes
Atomic Aggregate
Route Aggregation with AS_SET
Route Aggregation with Selective Advertisement of AS_Set
Default Route Advertisement
Default Route Advertisement Per Neighbor
Conditional Route Advertisement
Outbound Route Filtering
Backdoor Networks
Maximum Autonomous System
Maximum Prefix
Remove Private Autonomous System
Allow Autonomous System
Local Autonomous System
Configuration Scalability
IOS Peer Groups
IOS Peer Templates
IOS XR Configuration Templates
Summary
References in This Chapter
Chapter 15. BGP Best Path Selection
BGP Best Path Overview
Weight
Local Preference
Locally Originated via Network or Aggregate Advertisement
Accumulated Interior Gateway Protocol
Shortest AS_Path
Origin Type
Multi-Exit Discriminator
Missing MED behavior
Always Compare Med
BGP Deterministic MED
eBGP over iBGP
Lowest IGP Metric
Prefer the Oldest EBGP Path
Router ID
Minimum Cluster List Length
Lowest Neighbor Address
BGP ECMP
eBGP and iBGP Multipath
eiBGP Multipath
R1
R2
XR3
XR4
XR5
AS_Path Relax
Suboptimal Routing with Route Reflectors
Additional Route Reflector
Shadow Route Reflector
Shadow Session Route Reflector
BGP Add-Path
Summary
Further Reading
References in This Chapter
Part V: Multicast
Chapter 16. IPv4 Multicast Routing
Multicast Fundamentals
Multicast Addressing
Layer 2 Multicast Addresses
Internet Group Management Protocol
IGMP Snooping
IGMPv2
IGMPv3
Multicast Distribution Trees
Source Trees
Shared Trees
Protocol Independent Multicast
PIM Dense Mode
PIM Sparse Mode
PIM Shared and Source Path Trees
Shared Tree Join
Source Registration
PIM SPT Switchover
Designated Routers
Rendezvous Points
Static RP
Auto-RP
Candidate RPs
RP Mapping Agents
PIM Bootstrap Router
Candidate RPs
Reverse Path Forwarding
PIM Forwarder
Basic Multicast Configuration
Configure Rendezvous Points
Static RP
Auto-RP
BSR
Multicast Verification
Bidirectional PIM
Bidir-PIM Designated Forwarder
Summary
References in This Chapter
Chapter 17. Advanced IPv4 Multicast Routing
Interdomain Multicast Routing
Multiprotocol BGP
Multicast Source Discovery Protocol
MSDP Source Active Message Types
SA Messages
Keepalive Messages
MSDP Peers
MSDP Verification
MSDP Stub Networks
Rendezvous Point Redundancy
Auto-RP with Multiple RPs
Auto-RP Group Filtering
BSR with Multiple RPs
BSR Group Filtering
BSR RP Hash Algorithm
Static RP with Multiple RPs
Anycast RP
Source Specific Multicast
SSM Mapping
DNS SSM Mapping
Static SSM Mapping
Multicast Security
Auto-RP Scoping
Multicast Boundaries
Administratively Scoped Boundaries
Auto-RP Multicast Boundaries
BSR Multicast Boundaries
Auto-RP Cisco-RP-Announce Message Filtering
PIM-SM Source Registration Filtering
PIM-SM Accept RP
PIM Neighbor Control
PIM Register Rate Limit
Multicast Traffic Engineering
RPF Rules
Static Mroutes
MBGP
Static IGMP Joins
Multicast Troubleshooting
Mtrace
Summary
References in This Chapter
Part VI: IPv6
Chapter 18. IPv6 Addressing
IPv6 Address Structure
Text Representation Address Abbreviation
IPv6 Hexadecimal to Binary Conversion
IPv6 Address Types
Unicast
Global Unicast
Unique Local Unicast
Link-Local Unicast
Anycast
Multicast
Special IPv6 Addresses
Neighbor Discovery Protocol
Router, Prefix, and Parameter Discovery.
Redirect
IPv6 Stateless Address Autoconfiguration
Extended Unique Identifier
SLAAC Router Configuration
RA Options for DNS
Stateless DHCPv6
IOS Stateless DHCPv6 Configuration
IOS XR Stateless DHCPv6 Configuration
Stateless DHCPv6 Verification
Stateful DHCPv6, Relay Agent, and Relay Proxy
IOS Relay Agent Configuration
IOS Relay Agent Verification
IOS XR Proxy Agent Configuration
IOS XR Proxy Agent Verification
IOS Stateful DHCPv6 Server Configuration
IOS XR Stateful DHCPv6 Server Configuration
Stateful DHCPv6 Server Verification
IPv6 Address Resolution and Neighbor Unreachability Detection
Duplicate Address Detection
Summary
References in This Chapter
Chapter 19. IPv6 Routing
Static Routing
Static Route Configuration
Static Route Reference Chart for IPv6
EIGRPv6
EIGRPv6 Inter-Router Communication
EIGRPv6 Configuration
IOS EIGRPv6 Autonomous System Configuration
IOS EIGRPv6 Hierarchical Configuration
IOS XR EIGRPv6 Configuration
EIGRPv6 Verification
Summarization
Default Route
Route Filtering
EIGRP Configuration Command Reference Chart for IPv6
OSPFv3
OSPFv3 Inter-Router Communication
OSPFv3 Link-State Advertisement
OSPFv3 LSA Flooding Scope
OSPFv3 Configuration
IOS OSPFv3 Configuration
IOS XR OSPFv3 Configuration
OSPFv3 Verification
OSPFv3 Authentication
OSPFv3 Multiple Instances
OSPFv3 Configuration Command Reference Chart for IPv6
Integrated IS-IS for IPv6
IS-IS Inter-Router Communication
IS-IS Type-Length-Value
IS-IS Topology Modes
IS-IS Configuration
IOS Base Configuration
IOS XR Base Configuration
IOS Topology Mode Configuration
IOS XR Topology Mode Configuration
Verification
IS-IS Configuration Reference Chart for IPv6
Multiprotocol BGP for IPv6
Inter-Router Communication
BGP Configuration
IOS Base Configuration
IOS XR Base Configuration
BGP Verification
IPv6 over IPv4 BGP Sessions
BGP Configuration Command Reference Chart for IPv6
IPv6 Route Redistribution
Summary
References in This Chapter
Chapter 20. IPv6 Multicast Routing
IPv6 Multicast Routing Overview
IPv6 Multicast Address Mapping into MAC Address
Enabling Multicast Routing
Multicast Listener Discovery
Protocol Independent Multicast
PIM Sparse Mode
Static RP
Bootstrap Router
Embedded RP
IPv6 Multicast Verification Commands
Reverse Path Forwarding
Multicast Boundary Scope
PIM Source Specific Multicast
Summary
References in This Chapter
Index
Part VII: High Availability
Chapter 21. High Availability
Network Convergence Overview
Continuous Forwarding
Stateful Switchover
Nonstop Forwarding and Graceful Restart
OSPF
IS-IS
EIGRP
BGP
Nonstop Routing
NSR for OSPF
NSR for IS-IS
NSR for BGP
Nonstop Forwarding and Nonstop Routing Together
Failure Avoidance
Route Flap Dampening
IP Event Dampening
BGP Dampening
Event-Driven Failure Detection
Carrier Delay
BFD
Asynchronous Mode Without Echo
Asynchronous Mode with Echo
BFD Configuration for OSPF, IS-IS, and EIGRP
BFD Configuration for BGP
BFD Configuration for BGP Multihop
BFD Configuration for Static Routes
Fast Routing Convergence
IS-IS Convergence Tuning
OSPF Convergence Tuning
SPF Prefix Prioritization
BGP Convergence Tuning
Next-Hop Tracking
Minimum Route Advertisement Interval
TCP Performance
Fast Reroute
Loop-Free Alternate Fast Reroute
Loop-Free Condition Rules
LFA Protection Modes
OSPF LFA FRR
IS-IS LFA FRR
Shared Risk Link Group
BGP Prefix-Independent Convergence
BGP PIC Core
BGP PIC Edge
BGP PIC Edge Link and Node Protection
BGP PIC Edge with Next-Hop-Self
BGP Advertise Best External
BGP Additional Path
Summary
References in This Chapter
Appendixes
Appendix A. Decimal to Hex to Binary Tables
Appendix B. BGP Attributes
Code Snippets