Dst cache overflow with FC2 and FC3

[Kimmo Koivisto]

Hello

I'm having problems with dst cache overlow freezing my firewall.

Environment: 
- Dell PowerEdge 750, two integrated Intel e1000 ports,  acting as firewall
- I had FC2, now using FC3, with 2.6.9-1.681_FC3 kernel
- I had Dlink quad port ethernet card with sundance driver, now using quad 
port Intel e1000 card with e1000 driver
- 10Mbit/s internet connection with ~500 users behind the firewall, using 
iptables for nat.

Problem:
Sometimes (couple times in a month) network freezes and I get the following 
errors in /var/log/messages:

...
Jan 10 21:13:05 testfw kernel: dst cache overflow
Jan 10 21:13:05 testfw kernel: dst cache overflow
Jan 10 21:20:50 testfw kernel: dst cache overflow
Jan 10 21:20:50 testfw kernel: dst cache overflow
Jan 10 21:20:50 testfw kernel: dst cache overflow
...

Only reboot helps. 

I guess it's something nat/connection tracking related? I have checked out the 
number of lines in /proc/net/ip_conntrack during the freezes, last time there 
were 241 lines (wc -l /proc/net/ip_conntrack).

Is there anything that I could do to prevent this? Is this a known bug or 
should I file a bug report to the bugzilla?


Regards
Kimmo Koivisto