CNI Observability Comparison: Hubble vs Alternatives

Introduction

Network observability in Kubernetes is about understanding what’s happening in your cluster’s network layer: which services are talking to which, where traffic is being dropped, and why connections fail. Different CNI plugins approach observability differently—some provide rich, built-in tools like Cilium’s Hubble, while others rely on external monitoring solutions.

This comparison examines the observability capabilities of major CNI plugins: Cilium (with Hubble), Calico, Antrea, AWS VPC CNI, Flannel, and Weave Net. Understanding these differences helps teams choose the right CNI based on their observability requirements.

Observability Dimensions

We’ll compare CNIs across these dimensions:

1. Flow Visibility: Real-time visibility into network flows
2. Layer 7 Visibility: HTTP/gRPC-level observability
3. Service Dependency Mapping: Understanding service relationships
4. Policy Verification: Seeing which network policies are applied
5. Metrics Export: Integration with Prometheus/Grafana
6. Distributed Tracing: Request tracing across services
7. DNS Observability: DNS query and response tracking

Cilium with Hubble

Strengths

• eBPF-Based Observability: Kernel-level flow visibility with zero overhead
• Layer 7 Visibility: HTTP/gRPC protocol awareness
• Real-Time Service Map: Visual service dependency mapping
• Policy Verification: See which policies allow/deny flows
• DNS Tracking: Complete DNS query/response visibility
• Built-In UI: Web interface for flow visualization

Capabilities

# Real-time flow observation
hubble observe --follow

# Service dependency map
hubble service map

# Policy verification
hubble observe --verdict

# DNS queries
hubble observe --type dns

Limitations

• Cilium-Only: Works only with Cilium CNI
• No Historical Storage: Flows not persisted by default (requires external integration)
• Learning Curve: Requires understanding eBPF concepts for advanced use

Calico

Strengths

• Flow Logging: Basic flow logging capabilities
• Prometheus Integration: Exports metrics for Prometheus
• Network Policy Metrics: Tracks network policy allow/deny decisions
• External Tool Integration: Works with ELK stack, Splunk, etc.

Capabilities

• Metrics: Exposes Prometheus metrics for network policies and flows
• Flow Logs: Can export flow logs to external systems
• Policy Metrics: Tracks policy enforcement statistics

Limitations

• No L7 Visibility: Limited to L3/L4 (IP and port) visibility
• No Built-In UI: Requires external tools for visualization
• Basic Flow Logging: Less detailed than eBPF-based solutions
• No Real-Time Service Map: Requires external tools for service mapping

Antrea

Strengths

• OVS Flow Monitoring: Leverages Open vSwitch flow monitoring
• Prometheus Metrics: Exports detailed metrics
• Flow Aggregation: Aggregates flows for analysis
• Grafana Dashboards: Includes pre-built Grafana dashboards

Capabilities

• OVS Flows: Monitor Open vSwitch flow tables
• Metrics: Comprehensive Prometheus metrics
• Flow Export: Can export flows to external systems

Limitations

• No L7 Visibility: Limited to L3/L4 visibility
• OVS-Specific: Requires understanding OVS for advanced troubleshooting
• No Built-In Service Map: Requires external tools
• Less Real-Time: Flow aggregation may introduce delays

AWS VPC CNI

Strengths

• VPC Flow Logs: Integration with AWS VPC Flow Logs
• CloudWatch Integration: Native AWS monitoring integration
• Pod IP Visibility: Real pod IPs visible in AWS tools

Capabilities

• VPC Flow Logs: L3/L4 flow logs via AWS VPC Flow Logs
• CloudWatch Metrics: Network metrics in CloudWatch
• AWS Console: View network activity in AWS console

Limitations

• L3/L4 Only: No Layer 7 visibility
• AWS-Specific: Works only in AWS environments
• No Built-In Tools: Relies on AWS services for observability
• Limited Real-Time: VPC Flow Logs have delay
• No Service Map: Requires external tools for service mapping

Flannel

Strengths

• Simplicity: Simple architecture, easier to understand
• External Tools: Can use standard Linux networking tools

Capabilities

• Basic Monitoring: Standard Linux networking tools (tcpdump, netstat)
• External Integration: Can integrate with external monitoring tools

Limitations

• No Built-In Observability: No native observability features
• No Flow Visibility: No flow tracking or service mapping
• No Metrics: No built-in metrics export
• Manual Tools: Requires manual use of Linux networking tools

Weave Net

Strengths

• Weave Scope: Built-in visualization tool (separate product)
• Basic Flow Logs: Some flow logging capabilities
• Network Visualization: Visual network topology

Capabilities

• Weave Scope: Visual container and network topology
• Flow Logs: Basic flow logging
• Network Topology: Visual network map

Limitations

• Limited L7 Visibility: No HTTP/gRPC protocol awareness
• Scope Dependency: Requires Weave Scope for visualization
• No Real-Time Flows: Less real-time than eBPF-based solutions
• No Policy Verification: Limited network policy observability

Comparison Matrix

Use Case Recommendations

Choose Cilium+Hubble if:

• You need Layer 7 visibility (HTTP/gRPC)
• Real-time service dependency mapping is critical
• You want built-in observability without external tools
• Policy verification and DNS tracking are important

Choose Calico if:

• You need basic flow logging and metrics
• You have existing ELK/Splunk infrastructure
• L3/L4 visibility is sufficient
• You want Prometheus integration

Choose Antrea if:

• You’re using VMware infrastructure
• OVS flow monitoring meets your needs
• You want Grafana dashboards
• L3/L4 visibility is sufficient

Choose AWS VPC CNI if:

• You’re running EKS exclusively
• AWS-native monitoring (CloudWatch, VPC Logs) is preferred
• L3/L4 visibility is sufficient
• You want integration with AWS security tools

Choose Flannel if:

• Simplicity is the priority
• You’ll use external monitoring tools
• Basic networking is sufficient
• Observability is not a primary concern

Choose Weave Net if:

• You want basic network visualization
• Weave Scope integration is acceptable
• L3/L4 visibility is sufficient
• Simple setup is important

Operational Considerations

• Tool Integration: Consider how observability tools integrate with your existing monitoring stack
• Performance Impact: eBPF-based solutions (Cilium) have minimal overhead; others may vary
• Learning Curve: Built-in tools (Hubble) vs. external tools (Calico, Antrea)
• Cost: Cloud-native solutions (AWS VPC CNI) may have additional costs for logging
• Scalability: Consider how observability scales with cluster size

Summary

Network observability capabilities vary significantly across CNI plugins. Cilium with Hubble provides the most comprehensive observability with L7 visibility, real-time service maps, and built-in tools. Calico and Antrea offer good L3/L4 observability with Prometheus integration. AWS VPC CNI leverages AWS-native tools but is limited to AWS environments. Flannel and Weave Net provide basic observability or require external tools.

The choice depends on your observability requirements: if you need deep, real-time visibility with L7 awareness, Cilium+Hubble is unmatched. If L3/L4 visibility with external tool integration is sufficient, Calico or Antrea may be better choices. For AWS-only environments, VPC CNI with CloudWatch/VPC Logs provides adequate observability.