FreeBSD-6.1 reboots due to high mbufs

[Alessandro]

Hi,

I think the tcp connections remain in ESTABLISHED for a long time, it can depend from satellite link (high delay) or a problem with TCP timing in 6.1.  (The hardware configurations is the same of 4.x box?)

First of all you can try to set:
sysctl net.inet.tcp.inflight.enable=0
and then:
sysctl net.isr.direct=0
sysctl net.inet.tcp.slowstart_flightsize=4 or more


Can you upgrade FreeBSD? 
Can you run a "systat -vm 1" and "top"?
If you run netstat -in no errors are report?

If there are a lot of connections a lot of nmbclusters are used, you can run 
"netstat -na | grep ESTAB | wc -l".
The number of nmbcluster used is related with the number of connections.

Let me know.
Regards
Alessandro