[CentOS] Centos Router

[Ken Price]

>> My best tip for tuning performance:
>>
>> Don't until performance becomes an issue otherwise you have no
>> basis of determining whether performance has improved.
>
> Let me add a second tip:
>
> Don't tune a parameter unless you know what is does.
>

While probably not popular, those are very good tips.

I can give you some comparative performance info using CentOS3 and  
CentOS4.  CentOS5 will probably give equal or slightly better  
performance depending on specific configurations.

Harware:
4 Dell PowerEdge 350's (2 routers, 2 NAT firewalls)
PIII-850
512 Mb RAM

Bandwidth:
Average 25-35Mbps
Peak 80Mbps sustained for 1-2 hours
10k-25k connections

NAT Firewall:
CPU usage approx 2-8%

Router:
CPU usage approx 2-4%

With the above specs, I was approaching the connection threshold with  
512Mb RAM (32768 = theoretical max) and beginning to drop connections.  
  This was quickly fixed by adding an additional 512Mb RAM and  
adjusting the CONNTRACK_MAX accordingly.

Hope this helps.  All boxes were running Keepalived for failover.   
Fairly straight forward routing so no software used except routing  
tables, IP, and IP forwarding.

Hope this helps!
-Ken