Flood Rate-Limit Burst Tolerance and Output Actions

The flood rate-limit feature includes configurable burst tolerance levels and optional out-of-profile actions. This allows operators to fine-tune packet buffer handling for broadcast, multicast, and unknown-destination MAC traffic on a per-port basis.

Issue: The flood rate-limit feature enforces a fixed buffer bucket size for controlling broadcast, multicast, and unknown-destination MAC traffic. Network administrators cannot customize burst behavior or define actions when traffic exceeds the rate limit, making it difficult to balance strict rate enforcement with brief traffic spikes in bursty network environments.

Resolution: The flood rate-limit feature includes two enhancements: (1) a configurable burst-tolerance parameter that controls buffer handling at different tolerance levels, and (2) optional out-actions that specify actions when traffic exceeds the configured rate limit, such as logging events, generating SNMP traps, or disabling the port.

Key Capabilities:

• Burst tolerance levels provide control over buffer size: default retains the existing behavior, low applies aggressive burst suppression, medium applies moderate burst tolerance, and high applies permissive burst tolerance
• The switch applies burst tolerance on a per-port basis to individual flood rate-limit traffic types: broadcast, multicast, and unknown-destmac
• Out-of-profile actions log rate-limit events, generate SNMP traps, or disable the port when traffic exceeds the configured rate limit
• Multiple out-of-profile actions can be combined in a single configuration
• Configuration persists across reboots and is included in configuration backups
• Display commands show the configured burst tolerance and current rate-limit status per port
• Existing flood rate-limit configurations remain functional with the default burst tolerance and no actions

Configuration Syntax

Configure flood rate-limit with burst tolerance and out-of-profile actions:

configure ports [<port_list> | <port_group>] rate-limit flood [broadcast | multicast | unknown-destmac] <pps> { burst-tolerance [default | low | medium | high] } {out-actions [{log} {trap} {disable-port}] }

Parameters

• <pps> — Rate limit in packets per second
• burst-tolerance — Buffer size control: default uses existing behavior, low applies strict suppression, medium applies moderate tolerance, high applies permissive tolerance
• out-actions — Actions when traffic exceeds the limit: log logs the event, trap sends an SNMP trap, disable-port disables the port

Example Configuration

configure ports 1 rate-limit flood broadcast 2000 burst-tolerance low out-actions log

This configuration limits broadcast traffic on port 1 to 2000 packets per second with low burst tolerance and logs any rate-limit violations.

Display Rate-Limit Configuration

View the configured burst tolerance and rate-limit status:

show port 1 information detail

Sample Output

Port: 1 Virtual-router: None Type: UTP ... Broadcast Rate: 2000 packets-per-second Burst Tolerance: Low Multicast Rate: No-limit Unknown Dest Mac Rate: No-limit ...