Subject: IPFilter 3.3 on NetBSD 4.1 --- NMBCLUSTERS overflow, what is a sensible setting?
To: None <>
From: Aaron Roydhouse <>
List: tech-kern
Date: 08/28/1999 23:43:57
Hi, I'm having difficulty with NMBCLUSTERS overflowing on a NetBSD system
with IPFilter.

We're using IPFilter 3.3 on NetBSD 4.1 running on an Intel PIII with an
on-motherboard Intel EtherExpress and four 3Com 905B-TXNM cards. This is
out-of-the-box NetBSD 4.1 plus the recognition patch for the NM hardware
revision of the 3Com 905B-TX.

The default kernel config for NMBCLUSTERS is 256, or if GATEWAY is enabled
512. Using IPFilter 3.3 on four network interfaces with a fairly hefty
rule-set and NMBCLUSTERS=512, NMBCLUSTERS quickly overflowed (indicated by
console messages, networking pauses, and sometimes complete networking

Looking at other kernel configurations the largest setting for NMBCLUSTERS,
used by an FTP server, was NMBCLUSTERS=2048. So I increased our NMBCLUSTERS
to 2048. After a couple of days this value was overflowed too, resulting in
all four network interfaces ceasing to operate (but no panic or other
noticeable effects).

The actual overflow was coincident with a lot of FTP activity---So I'm not
clear whether it is time or an activity level that causes the overflow.

So I have lots of questions...

*** Anyone having similar experiences?

*** What values for NMBCLUSTERS are other NetBSD/*BSD users using?

*** Does using IPFilter increase the use of NMBCLUSTERS on NetBSD?

*** Is it reasonable that IPFilter might need NMBCLUSTERS > 2048  ?

*** How can I find out how many NMBCLUSTERS are in use at any given time?

*** Could this be an NMBCLUSTERS leak? Or do I just need a bigger setting?

I still have the machine running, untouched since the networking failed
after the NMBCLUSTERS overflow. So if there is any extra info I can supply,
just tell me.