PortFast Question

[Josh Sukol <secnews () gmail com>]

I am running a small network using four Cisco Catalyst 2950 switches. 
I am in the process of configuring a new software package that uses
some proprietary hardware that connects to the  network via Ethernet. 
When plugged into the network the device would connect for a minute or
two and than connectivity would drop (i.e. ping would fail, and the
light on the switch would turn from green to amber)  This pattern
continued for as long as the device was plugged into the network.  The
cabling was checked and tested with other equipment and there were no
other problems.

After trying several other things I eventually started changing the
ethernet port settings on the switch itself and found that by enabling
portfast the device functioned fine.  I have found very little
information about port fast security issues.  I was able to find and
did read up on PortFast BPDU guard and potential DoS using malformed
packets.  Are there any other security issues that effect me enabling
Portfast on specific ports that connect back to a single device?  Are
there any other ways to solve this problem that might allow me to
sidestep this potential security issues all together?

- Slightly Off Topic - 
If anyone knows why this behavior occurs and why enabling portfast
fixes the connectivity issue I would be very interested to a hear an
explanation.


Thanks in advance for the wisdom!

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