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IP Routing
Troubleshooting TechNotes
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Border Gateway Protocol (BGP)
Classless Interdomain Routing (CIDR)
Enhanced Interior Gateway Routing Protocol (EIGRP)
Integrated Intermediate System-to-Intermediate System (IS-IS)
Interior Gateway Routing Protocol (IGRP)
Multiprotocol BGP (MBGP)
Open Shortest Path First (OSPF)
Routing Information Protocol (RIP)
Cisco Optimized Edge Routing (OER)
Border Gateway Protocol (BGP)
IOS Implementation of the iBGP PE-CE Feature
Troubleshoot BGP Neighbor Flaps with MTU
Configure IP Addresses and Unique Subnets for New Users
Next-Hop Mismatch and BGP Inactive Routes Tech Note
Troubleshoot Common BGP Issues
Describe Administrative Distance
Configure BGP Routers for Optimal Performance and Reduced Memory Consumption
Select BGP Best Path Algorithm
Examine Border Gateway Protocol Case Studies
BGP Peer Groups
BGP Policy Accounting and BGP Policy Accounting Output Interface Accounting Features
BGP Prefixes Filters with 4-byte AS Numbers
Block One or More Networks From a BGP Peer
Border Gateway Protocol (BGP) Optimal Route Reflection
Use Multi-Exit Discriminator to Select Best Path for BGP Router
How the bgp deterministic-med Command Differs from the bgp always-compare-med Command
How to Block One or More Networks From a BGP Peer
(ZIP - 43 KB)
Removing Private Autonomous System Numbers in BGP
Route Target Constraint
The "%TUN-5-RECURDOWN" Error Message and Flapping EIGRP/OSPF/BGP Neighbors Over a GRE Tunnel
Troubleshoot Flapping BGP Routes (Recursive Routing Failure)
Troubleshoot High CPU Caused by the BGP Scanner or Router Process
Troubleshoot Border Gateway Protocol Routes that Do Not Advertise
Understand BGP RIB-Failure and BGP Suppress-Inactive Command
Understand Next Hop Set in iBGP Advertisements on Nexus NX-OS vs Cisco IOS
Understand and Troubleshoot CEF on Cisco IOS XE Routers
Understand the Importance of BGP Weight Path Attribute
Understanding Policy Routing
Understand the Redistribution of OSPF Routes into BGP
Understand Route Aggregation in BGP
Unsupported Capabilites Cause BGP Peer Malfunction
Use Regular Expressions in BGP
What Does the "#%BGP-3-INSUFCHUNKS: Insufficient chunk pools for aspath" Error Message Mean?
When Are ICMP Redirects Sent?
Troubleshoot BGP Neighborship Connection Issues
BGP Conditional Advertisement Feature
Change in Behavior for VPN Route Advertisement in BGP Starting 7.1
Cisco IOS-XR BGP with MPLS Designs
Configure Advanced Options for BGP on FTD
Configure Allowas-in Feature in BGP
Configure MD5 Authentication Between BGP Peers
Configure Mutual Redistribution Between EIGRP and BGP
Configure Route Redistribution on Nexus Switches
Configure an Upstream Provider Network with BGP Community Values
Configure and Verify BGP Path Selection in IOS-XR
Configure and Verify Double-sided Virtual vPC
Configure eBGP HA with SFTD/ASA and Cloud Service Provider
Configure iBGP and eBGP with or without a Loopback Address
Configure the BGP Local-AS Feature
Deploy BGP Soft Next-Hop in Cisco IOS XR
How to Poll BGP Neighbours under VRF on ISR and ASR routers with SNMP v3
Labeled and Unlabeled Together on one BGP Neighbor on IOS-XR
Troubleshoot BGP Virtual Memory (RLIMIT) Issue on IOS XR
Troubleshoot Border Gateway Protocol Basic Issues
Troubleshoot IGP Flaps, Packet Loss, or Tunnel Bounce across a VPN Tunnel with EEM and IP SLAs
Troubleshoot In-line BGP VPNv4 RR with Same Route-Distinguisher and 'cef encap-sharing disabled'
Troubleshoot Slow BGP Convergence Due to Suboptimal Route Policies on IOS-XR
Troubleshoot why EIGRP External Route Is Preferred Over BGP
Understand BGP MED Attribute
Understand BGP RPKI With XR7 Cisco8000 Whitepaper
Understand Basic BGP Troubleshoot
Understand Load Sharing with BGP in Single/Multihomed Environments
Verify Path MTU Discovery on Cisco IOS XR and BGP
Classless Interdomain Routing (CIDR)
Configure IP Addresses and Unique Subnets for New Users
Enhanced Interior Gateway Routing Protocol (EIGRP)
EIGRP on SVTI, DVTI, and IKEv2 FlexVPN with the "IP[v6] Unnumbered" Command Configuration Example
Configure IP Addresses and Unique Subnets for New Users
Describe Administrative Distance
Configuration Notes for the Implementation of EIGRP over Frame Relay and Low Speed Links
Understand and Use the Enhanced Interior Gateway Routing Protocol
Filtering Routing Updates on Distance Vector IP Routing Protocols
How Does Unequal Cost Path Load Balancing (Variance) Work in IGRP and EIGRP?
Understand how the Passive Interface Feature Works in EIGRP
Introduction to EIGRP
OSPF and EIGRP Neighbor Loss, RIP and IGRP Update Loss after Upgrading to Cisco IOS 11.2 or Later
Preventing Duplicate EIGRP Router IDs
Redistributing Between Classful and Classless Protocols: EIGRP or OSPF into RIP or IGRP
Configure Route Selection for Routers
The "%TUN-5-RECURDOWN" Error Message and Flapping EIGRP/OSPF/BGP Neighbors Over a GRE Tunnel
Troubleshoot EIGRP Common Issues
Troubleshooting EIGRP
(ZIP - 107 KB)
Troubleshooting EIGRP
Understanding IPX-EIGRP
Understanding Policy Routing
What Does the EIGRP DUAL-3-SIA Error Message Mean?
When Are ICMP Redirects Sent?
Configure EIGRP IPV6 on ASA
Configure EIGRP to Influence Path Selection
Configure Mutual Redistribution Between EIGRP and BGP
Configure Route Redistribution on Nexus Switches
Manipulate EIGRP from Higher Metric to Lower Metric
Troubleshoot IGP Flaps, Packet Loss, or Tunnel Bounce across a VPN Tunnel with EEM and IP SLAs
Integrated Intermediate System-to-Intermediate System (IS-IS)
Configure IP Addresses and Unique Subnets for New Users
Describe Administrative Distance
Create IS-IS Topology from CLI Output of IOS-XR Router
IS-IS Network Types and Frame Relay Interfaces
IS-IS Network Types and Frame Relay Interfaces
(ZIP - 52 KB)
IS-IS Route Leaking Overview
Intermediate System-to-Intermediate System (IS-IS) TLVs
MTU Mismatch Problem in IS-IS
Understanding IS-IS Pseudonode LSP
Understanding Policy Routing
Uses of the Overload Bit with IS-IS
When Are ICMP Redirects Sent?
Troubleshoot IS-IS Adjacency Issues
Interior Gateway Routing Protocol (IGRP)
Configure IP Addresses and Unique Subnets for New Users
Describe Administrative Distance
Behavior of RIP and IGRP When Sending and Receiving Updates
Filtering Routing Updates on Distance Vector IP Routing Protocols
How Does Unequal Cost Path Load Balancing (Variance) Work in IGRP and EIGRP?
How Split Horizon Affects RIP/IGRP Routing Updates when Secondary Addresses Are Involved
IGRP Metric
OSPF and EIGRP Neighbor Loss, RIP and IGRP Update Loss after Upgrading to Cisco IOS 11.2 or Later
Redistributing Between Classful and Classless Protocols: EIGRP or OSPF into RIP or IGRP
Understanding Policy Routing
When Are ICMP Redirects Sent?
Why Doesn't RIP or IGRP Support Discontiguous Networks?
Why Don't RIPv1 and IGRP Support Variable-Length Subnet Mask?
An Introduction to IGRP
Multiprotocol BGP (MBGP)
Describe Administrative Distance
Understand Load Sharing with BGP in Single/Multihomed Environments
Open Shortest Path First (OSPF)
Down-bit Ignore Feature in OSPFV2 PE-CE Scenario on Cisco NX-OS
Guide to OSPF Application on the CSS 11000
Configure IP Addresses and Unique Subnets for New Users
Describe Administrative Distance
Why OSPF Demand Circuit Keeps Bringing Up the Link
Change of Default OSPF and IS-IS SPF and Flooding Timers and iSPF Removal
Common Routing Problem with OSPF Forwarding Address
Guide to OSPF Application on the CSS 11000
Configure Initial Configurations for OSPF over Non-Broadcast Links
OSPF Demand Circuit Feature
OSPF External path selection: External Type-2 (E2) VS NSSA Type-2 (N2)
Troubleshoot OSPF Neighbor Problems
Understand OSPF Neighbor States
Configure the OSPF Not-So-Stubby Area (NSSA)
Redistribute OSPF Among Different OSPF Processes
OSPF Virtual Links: Transit capability
OSPF and EIGRP Neighbor Loss, RIP and IGRP Update Loss after Upgrading to Cisco IOS 11.2 or Later
OSPF show Commands Respond Slowly
OSPF, MTU and LSA Packing Tech Note
Problems with Running OSPF in NBMA and Broadcast Mode over Frame Relay
Redistributing Between Classful and Classless Protocols: EIGRP or OSPF into RIP or IGRP
Redistributing Connected Networks into OSPF
Suboptimal Routing When Redistributing Between OSPF Processes
The "%TUN-5-RECURDOWN" Error Message and Flapping EIGRP/OSPF/BGP Neighbors Over a GRE Tunnel
The Effects of the Forwarding Address on Type 5 LSA Path Selection
Troubleshooting Duplicate Router IDs with OSPF
Troubleshoot Common Problems with OSPF
Understand Selection of Forwarding Address in OSPF
Understanding OSPF LSA-ID Conflict : %OSPF-4-CONFLICTING_LSAID
Understanding Policy Routing
What Do
%OSPF-4-ERRRCV
Error Messages Mean?
Understand Show IP OSPF Neighbor Command Output
When Are ICMP Redirects Sent?
Troubleshoot OSPF Neighbors Stuck in Exstart/Exchange State
Troubleshoot Open Shortest Path First Route Database Issues
Why Does the show ip ospf neighbor Command Reveal Neighbors Stuck in Two-Way State?
Why Does the show ip ospf neighbor Command Reveal Neighbors in the Init State?
Why Doesn't OSPF Form Adjacency on a PRI, BRI, or Dialer Interface?
Configure Authentication in Open Shortest Path First
Configure OSPF Connection in a Virtual Link Environment
Configure Route Redistribution on Nexus Switches
Configure and Verify Double-sided Virtual vPC
Designing Large-Scale Stub Networks with ODR
OSPF Configuration Management with SNMP
Troubleshoot IGP Flaps, Packet Loss, or Tunnel Bounce across a VPN Tunnel with EEM and IP SLAs
Understand the Redistribution of OSPF Routes into BGP
Use OSPFv3 Configuration Example
Routing Information Protocol (RIP)
Configure IP Addresses and Unique Subnets for New Users
Describe Administrative Distance
Behavior of RIP and IGRP When Sending and Receiving Updates
Filtering Routing Updates on Distance Vector IP Routing Protocols
How Split Horizon Affects RIP/IGRP Routing Updates when Secondary Addresses Are Involved
ICMPv6 Packet Types and Codes
OSPF and EIGRP Neighbor Loss, RIP and IGRP Update Loss after Upgrading to Cisco IOS 11.2 or Later
Redistributing Between Classful and Classless Protocols: EIGRP or OSPF into RIP or IGRP
Understanding Policy Routing
When Are ICMP Redirects Sent?
Why Doesn't RIP or IGRP Support Discontiguous Networks?
Why Don't RIPv1 and IGRP Support Variable-Length Subnet Mask?
Cisco Optimized Edge Routing (OER)
Introduction to IWAN and PfRv3
Interior Gateway Protocol (IGP)
Troubleshoot IGP Flaps, Packet Loss, or Tunnel Bounce across a VPN Tunnel with EEM and IP SLAs
On-Demand Routing (ODR)
Designing Large-Scale Stub Networks with ODR
BGP Table Version
30/Sep/2013
External LSA with Overlapping Subnets in OSPF
11/Nov/2013
IP Subnet Calculator
Local Host Routes Installed in the Routing Table on Cisco IOS and Cisco IOS-XR
10/Jul/2013
NetPro Discussion Forums on LAN, Switching & Routing
Policy Routing and Its Impact on ESP and ISAKMP Packets with Cisco IOS
30/Oct/2013
Software Advisor - Choose The Software For Your Network Device
BGP Route Reflection and Multiple Cluster IDs
14/Sep/2015
Compare OSPF Forwarding Address Behaviour on IOS and IOS-XR
31/Jul/2018
IOS XR BGP Best Practice: eBGP Transit AS Route Advertisment
19/Apr/2016
IP OSPF MTU-Ignore Command
03/Dec/2015
IS-IS Hello Padding Behavior
15/Dec/2015
Message "IPRT-3-RIB_LOOP" - Resolution Loop Formed by Routes in RIB
13/Jan/2016
Native Multicast Flow - Any-Source Multicast Model
12/Jan/2018
OSPF Complex Error Message Troubleshooting
01/Apr/2015
Configure a Next Hop IP Address for Static Routes
10/Jul/2023
Troubleshoot the "OSPF Neighbor Down: Too Many retransmissions" Error Message
14/Jan/2016
Use the BGP "Slow Peer" Feature to Resolve Slow Peer Issues
16/Jun/2015
Why Can't I Browse the Internet when Using a GRE Tunnel?
10/Aug/2005
CAT 6500 and 7600 Series Routers and Switches TCAM Allocation Adjustment Procedures
Configure Administrative Distance of Specific Received Route
Configure Nexus L2 EVPN over SR MPLS with VPC Anycast Gateway
Configure OSPFv3 in an NSSA Area to Enable Translation of Type-7 LSA with Zero Forwarding Address
Configure Protocol Redistribution for Routers
Configure Route-Maps Applied with Redistribution Command
Configure Topology Independent - Loop Free Alternate
Configure VRF Leaks on IOS XE
Consider SNMP Counters: Frequently Asked Questions
Quick Start Guide - Data Collection for Various Routing & Platform (IOS & IOS-XE Routers) Related Issues
TCP/IP Overview
Troubleshoot Bidirectional Forwarding Detection in Cisco IOS XE
Troubleshoot EVPN/VxLAN in Multisite Environment
Troubleshoot RIB Error Message "ROUTING-RIB-3-LABEL_ERR_ADD: Add local-label"
Understand Configuration Register Usage on all Routers
Understand Host and Subnet Quantities
Understand the Ping and Traceroute Commands
Use the Standby Preempt and Standby Track Commands
Verify and Troubleshoot Basic NAT Connectivity
Verify and Troubleshoot Basic NAT Operations
eBGP peering over vPC on Nexus
Support Documentation
All Support Documentation for this protocol