SPAN Scaling Challenge

I’m facing a mini scaling challenge with Cisco SPAN (Switched Port ANalyzer) session and thought it would be good to share it with you fine folk.

SPAN Challenge

A 3750X switch is currently SPAN-ing a 10Gbps interface to a 1Gbps egress port. A server is directly attached and is using dump cap to capture a subset (5%) of the overall traffic for analysis.

The 10G link under-utilised, but is running close to the 1Gbps traffic limit in the Rx direction. Tx traffic is very low by comparison, but the SPAN session is capturing both directions.

The aggregated flow from both directions is overrunning the SPAN destination 1Gbps port. The challenge is to ensure we can continue to capture without discarding any interesting data. Let’s explore the options together.

Continue reading