Common Issues

Chapter Overview

This section identifies the most common VXLAN deployment issues, their symptoms, root causes, and resolution strategies. Learn systematic troubleshooting approaches for VXLAN networks.

Top VXLAN Issues

The most frequently encountered problems in VXLAN deployments:

Critical Issues
  • BGP EVPN session failures
  • VTEP reachability problems
  • VNI configuration mismatches
  • Underlay connectivity issues
  • MTU fragmentation
Performance Issues
  • Packet loss and drops
  • High latency
  • Bandwidth limitations
  • CPU utilization spikes
  • Memory exhaustion

Issue Classification

Systematic classification of VXLAN problems:

Category Symptoms Common Causes Impact
Control Plane BGP session down, Missing routes Authentication, Connectivity Complete failure
Data Plane Packet loss, No traffic flow MTU, Encapsulation Partial failure
Configuration Inconsistent behavior Mismatched VNIs, RTs Intermittent issues
Performance High latency, Drops Resource exhaustion Degraded performance

BGP EVPN Issues

Most common BGP EVPN control plane problems:

BGP Session Troubleshooting

# Check BGP neighbor status
show bgp l2vpn evpn summary
show bgp l2vpn evpn neighbors

# Common BGP issues and solutions:

# Issue 1: BGP session not establishing
# Symptoms: Neighbor in Active/Connect state
# Verification commands:
ping 192.168.1.100 source loopback0
show bgp l2vpn evpn neighbors 192.168.1.100
show run | section "router bgp"

# Issue 2: Routes not being advertised
# Symptoms: Empty BGP table
# Verification commands:
show bgp l2vpn evpn
show bgp l2vpn evpn vni 10100
show bgp l2vpn evpn route-type 2

Critical Troubleshooting Tips

  • Always check underlay first: Most VXLAN issues are underlay problems
  • Verify configurations match: Inconsistent configs cause most issues
  • Check both directions: VXLAN issues can be asymmetric
  • Monitor during changes: Watch for side effects
  • Use debug sparingly: Enable only when necessary
Previous: Integration with SDN Next: Connectivity Problems

Connectivity Problems

Chapter Overview

This section focuses on VXLAN connectivity issues, including layer 2 and layer 3 connectivity problems, their symptoms, and resolution strategies.

Layer 2 Connectivity Issues

Common layer 2 connectivity problems in VXLAN networks:

Complete L2 Failure
  • No MAC learning
  • VXLAN tunnel down
  • BGP routes missing
  • VNI configuration error
Partial L2 Failure
  • Intermittent connectivity
  • Unidirectional traffic
  • Broadcast not working
  • ARP resolution fails

L2 Connectivity Troubleshooting

Systematic approach to troubleshooting L2 connectivity:

L2 Connectivity Diagnostic

# Step 1: Check VLAN and VNI configuration
show vlan brief
show vlan vn-segment
show nve vni

# Step 2: Verify VXLAN tunnel status
show nve interface
show nve peers

# Step 3: Check MAC address learning
show mac address-table
show mac address-table dynamic
show l2route evpn mac all

# Step 4: Verify BGP EVPN Type-2 routes
show bgp l2vpn evpn route-type 2
show bgp l2vpn evpn vni 10100

Connectivity Troubleshooting Tips

  • Start with basic ping and work up to applications
  • Use packet capture to analyze actual traffic
  • Test from multiple source and destination points
  • Document connectivity requirements before troubleshooting
  • Use monitoring tools to identify patterns
  • Consider time-based and load-based connectivity issues
Previous: Common Issues Next: Performance Issues

Performance Issues

Chapter Overview

This section covers VXLAN performance issues including latency, throughput, packet loss, and resource utilization problems. Learn to identify, analyze, and resolve performance bottlenecks.

Performance Metrics Overview

Key performance indicators for VXLAN networks:

Latency

Round-trip time
Jitter variance

Throughput

Bandwidth utilization
Packets per second

Packet Loss

Drop rate
Error statistics

Resources

CPU usage
Memory utilization

Latency Issues

Identifying and resolving latency problems:

Latency Troubleshooting

# Measure latency
ping 192.168.1.2 source loopback0 repeat 100
ping 192.168.100.10 source 192.168.100.1 repeat 100

# Check interface delays
show interface nve1 | include "delay"
show interface ethernet1/1 | include "delay"

# Monitor latency over time
ip sla 1
 icmp-echo 192.168.1.2 source-ip 192.168.1.1
 frequency 10
ip sla schedule 1 life forever start-time now

Performance Optimization Tips

  • Monitor performance continuously, not just during issues
  • Use hardware acceleration when available
  • Optimize MTU for your environment
  • Implement proper QoS policies
  • Consider the entire network path
  • Regular performance testing and validation
Previous: Connectivity Problems Next: Debug Commands

Debug Commands

Chapter Overview

This section provides comprehensive debug commands for VXLAN troubleshooting across different platforms. Learn when and how to use debug commands effectively and safely.

Debug Command Safety

Warning: Debug commands can significantly impact system performance and should be used with caution in production environments. Always:

  • Enable debug commands only when necessary
  • Use specific debug filters to limit output
  • Disable debug commands immediately after use
  • Monitor CPU utilization during debug sessions
  • Consider maintenance windows for intensive debugging

BGP EVPN Debug Commands

Debug commands for BGP EVPN control plane troubleshooting:

BGP EVPN Debugging - Cisco NX-OS

# Enable BGP EVPN debugging
debug bgp l2vpn evpn
debug bgp l2vpn evpn events
debug bgp l2vpn evpn updates
debug bgp l2vpn evpn keepalives

# Debug specific neighbor
debug bgp l2vpn evpn neighbor 192.168.1.100
debug bgp l2vpn evpn neighbor 192.168.1.100 updates

# Debug specific VNI
debug bgp l2vpn evpn vni 10100
debug bgp l2vpn evpn route-type 2

# Monitor debug output
terminal monitor
show logging logfile | include "BGP\|EVPN"

# Disable debugging
no debug bgp l2vpn evpn
no debug all

Debug Command Reference

Quick reference for common debug commands:

Component Cisco NX-OS Juniper Arista
BGP EVPN debug bgp l2vpn evpn set protocols evpn traceoptions debug bgp evpn
VXLAN Tunnels debug nve set interfaces vxlan traceoptions debug vxlan
MAC Learning debug l2rib mac set protocols l2-learning traceoptions debug vxlan mac

Debug Best Practices

  • Use specific debug filters to limit output
  • Monitor system resources during debug sessions
  • Disable debugging immediately after use
  • Save debug output for later analysis
  • Use debug commands in lab environments first
  • Document debug findings for future reference
Previous: Performance Issues Next: VXLAN Best Practices