Next, I kept the single 10-Gig link between the two switches and ran eight copper Gig connections to each switch, balanced among three six-port Gig blades on the 4506, and across several ASICs in the 4948. Running fully meshed throughput tests with packet sizes ranging from 64 to 1,518 bytes between the two switches, I again witnessed wire-rate performance with packet loss measured in hundredths of a percent. With this same test bed, I ran more tests to exercise the address learning and broadcast forwarding functions, and again the 4506 performed flawlessly.

Per VLAN, per port

It was time to give the per-port and per-VLAN QoS a try. I constructed a rather large QoS match list comprising more than 500 TCP and UDP (User Datagram Protocol) ports and bound that ACL (access control list) to a QoS configuration on every Gig port on the 4506. The QoS parameters were to limit the bandwidth of any inbound or outbound TCP connection that matched on the ACL to 20Mbps, dropping packets that exceeded this threshold. Again running with the 16 Gig connections to either switch, I ran another meshed test with the Spirent TestCenter SPT-5000A. I still couldn't make the 4506 break a sweat.

I then adapted the test on a per-VLAN basis, assigning several VLANs to each active port to simulate a VoIP/workstation scenario, this time limiting the bandwidth in a similar fashion on one specific VLAN, and reran the tests. Again, the 4506 performed with aplomb, successfully keeping up with the traffic flow at the highest levels that I could push it.

In another test run, I began the meshed streaming test with QoS disabled on the 4506 and then enabled QoS halfway through the test. There was a several-second hesitation in the CLI but no other ramifications of popping the clutch in this fashion, as might be necessary in production. The limiting began immediately and performed as expected.