[Bridge] Benchmarking bridging vs. routing on same hardware/network

dan-linuxbridge at unpossible.com dan-linuxbridge at unpossible.com
Wed Jan 26 12:52:13 PST 2005

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?  

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