I have been running benchmarks to compare the performance of bridging to routing on the same hardware. The bridge/router system is a dual Opteron 246 (2.0Ghz); Tyan 2882 motherboard; 2 GB PC3200 memory (1 GB in each CPU's bank; 128bit configuration); dual e1000 based NIC; PCI-X 133Mhz; 2.6.9 Kernel; NAPI enabled in the kernel and the NIC drivers; CPU affinity ties each eth to a specific CPU; system otherwise idle. My test configuration is: Packet Generator System <--> Bridge/Router <--> Packet Recipient The network and hosts are otherwise idle. Using pktgen (the Linux packet generator) I can send 459,000pps through this hardware when it is configured as a router. I only get 252,000pps through the hardware when configured as a bridge. Needless to say, I use two IP subnets when routing, and a single subnet while bridging. Also, when routing I set the mac addr destination for pktgen to the router interface (otherwise it won't pick up the packets), whereas when bridging I set it to the recipient's mac address. Any ideas why the performance of the bridge is so bad?
