pf/Linux/Scrub

[Per olof Ljungmark]

I was reading about OpenVPN in order to make a possible test bed when I 
came across the following statement:

* If run through a firewall using OpenBSDs packet filter PF and the
  filter rules include a "scrub" directive, you may get problems talking
  to Linux hosts over the tunnel, since the scrubbing will kill packets
  sent from Linux hosts if they are fragmented. This is usually seen as
  tunnels where small packets and pings get through but large packets
  and "regular traffic" don't.
Is this a valid comment? I'm not sure I understand what they mean...

Thanks,

/per