- Unnecessary traffic refers to network data that consumes bandwidth, processing power, and resources without providing meaningful value to end users or network operations
- Primary causes include broadcast storms, routing loops, duplicate transmissions, and inefficient protocols generating excessive overhead
- Understanding and mitigating unnecessary traffic is critical for network performance optimization and troubleshooting
Common Sources of Unnecessary Traffic
- Broadcast storms: Occur when broadcast frames flood the network, often caused by switching loops or misconfigured devices
- Routing loops: Packets circulate endlessly between routers due to incorrect routing table entries or convergence issues
- Duplicate frames: Result from spanning tree protocol (STP) misconfiguration or network interface card (NIC) errors
- Chatty protocols: Applications or services that generate excessive keepalive messages, status updates, or polling traffic
- Inefficient multicast: Poorly configured multicast routing causing unnecessary replication across network segments
Traffic Types and Mitigation Strategies
| Traffic Type | Cause | Mitigation Strategy | Protocol/Feature |
|---|---|---|---|
| Broadcast Storm | Switching loops | Enable STP/RSTP | 802.1D/802.1w |
| Routing Loop | Convergence issues | Implement split horizon, poison reverse | RIP, EIGRP, OSPF |
| Unknown Unicast Flooding | Missing MAC entries | Proper VLAN design, MAC aging timers | CAM table management |
| Multicast Flooding | No IGMP snooping | Enable IGMP snooping on switches | IGMP v2/v3 |
| ARP Broadcast Excess | Large broadcast domains | Implement VLANs, smaller subnets | VLAN segmentation |
Detection Methods
- Network monitoring tools: Use SNMP monitoring to track interface utilization and error rates
- Protocol analyzers: Wireshark or similar tools to identify traffic patterns and anomalies (capture filters help isolate specific traffic types)
- Switch port statistics: Monitor broadcast/multicast packet counts using
show interfacescommands - Baseline comparison: Establish normal traffic patterns to identify deviations indicating unnecessary traffic
Vocabulary
Broadcast Storm: Uncontrolled propagation of broadcast frames that can saturate network links and overwhelm device processing capabilities
Convergence: Process by which routing protocols reach agreement on network topology after a change occurs
Split Horizon: Routing loop prevention mechanism that prevents a router from advertising a route back through the interface it learned the route from
IGMP Snooping: Layer 2 feature that examines IGMP messages to intelligently forward multicast traffic only to interested receivers
CAM Table: Content Addressable Memory table that stores MAC address to port mappings on switches
Notes
- Always enable spanning tree protocol on switched networks to prevent loops, even in seemingly simple topologies
- Monitor broadcast traffic levels - sustained broadcast rates above 10% of link capacity typically indicate problems
- Use VLANs strategically to contain broadcast domains (broadcast traffic doesn’t cross VLAN boundaries)
- Implement proper multicast routing and IGMP snooping to prevent unnecessary multicast flooding
- Consider using unicast routing protocols with fast convergence (like EIGRP or OSPF) instead of distance-vector protocols in complex topologies
- Regular network baseline monitoring helps identify gradual increases in unnecessary traffic before they become critical issues
- Routing loops can be detected by TTL expiration messages in ICMP - look for patterns in network monitoring