problem in usb2usb network

[Kiselev]

Hello, all
Problem: vanishes connection in the usb lan
I make usb  network (usb2usb lan).
   1.    I do everything as it is written in man 4 udbp:
kldload netgraph
kldload udbp
Result :
udbp0: Prolific Technology Inc. PL2302 Host-Host interface, rev 1.00/0.01, 
addr
2, iclass 255/0.
   2.  Then doing:  ngctl mkpeer udbp0: iface data inet, ifconfig ng0 
10.0.0.1 10.0.0.2,
on both hosts (IP addresses reversed).
   3.  Ping from 10.0.0.1 to 10.0.0.2  there are no more than 1 minutes, 
and then disappears.
ОS: >= 5.2.1
Firewall disabled
Why it occurs and how it liquidate?
  Thanks in advance
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best regards