[TriLUG] reverse ssh through firewall/NAT with a twist

[Joseph Mack NA3T]

On Sat, 15 Nov 2014, Bill Farrow wrote:

> Traversing NAT on your firewall is nothing new. Skype does this all the time.

hmm. I didn't know that a NAT router would accept a SYN packet.

http://en.wikipedia.org/wiki/TCP_hole_punching

I thought part of NAT was the security offered by the inability to get to 
servers on the inside of the NAT device because it wouldn't accept a SYN packet.

Of course with UDP anything goes

http://en.wikipedia.org/wiki/UDP_hole_punching

I hadn't really thought about how Skype or bittorrent worked. I'd assumed a 3rd 
machine was always involved, but exactly how I hadn't thought about. With 
Bittorrent being UDP, I decided it was too complicated to think about. I hadn't 
bothered to think about how Skype worked.

Joe

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Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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