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Re: NAT and IPSEC INCOMPATIBLE???



Let me repeat my question: If a packet comes in on port X on the NAT
gateway, how do you know whether the packet really goes to port X on
host Y or port X on host Z?  Remember, this is a protocol with a known
port (port X)... It ALWAYS sits on port X.  So, how do you address
"port X on host Y" when "host Y" is behind a NAT gateway?

-derek

Pakulski Krzysztof-LKP014 <Krzysztof_Pakulski-LKP014@email.mot.com> writes:

> 
> I believe that one of the possibilities to make static binding.
> 
> If something comes to port X on NAT gateway, it is forwarded to port Y on
> host Z, if policy allowes that.
> 
> Krzysztof
> > ----------
> > From: 	Derek Atkins[SMTP:warlord@MIT.EDU]
> > Sent: 	Thursday, June 10, 1999 3:45 PM
> > To: 	pcalhoun@eng.sun.com
> > Cc: 	Pyda Srisuresh; danmcd@Eng.Sun.Com; johnbr@elastic.com;
> > ipsec@lists.tislabs.com
> > Subject: 	Re: NAT and IPSEC INCOMPATIBLE???
> > 
> > How can you do port address translation on known incoming ports?  For
> > example, what do I do if I need to get to port X on your host, which
> > is sitting behind a NAT firewall?  Obviously I don't know you're
> > sitting behind a NAT gateway; how is the NAT gateway supposed to know
> > that a packet coming to port X is destined for host Y or host Z, both
> > of whom may be using these NAT-unfriendly protocols?
> > 
> > And no, an answer of "don't use NAT-unfriendly protocols" is not a
> > valid answer, as many of these protocols were developed years (or
> > decades) before NAT.
> > 
> > -derek
> > 
> > "pcalhoun@eng.sun.com" <Pat.Calhoun@Eng.Sun.Com> writes:
> > 
> > > 
> > > agreed, but my comment was directed to the use of NAT in hotels. It was
> > not
> > > inteded to be IPSec specific. I had *assumed* that they were doing port
> > > translation (to conserve addresses).
> > > 
> > > 
> > > PatC
> > > > 
> > > > Pat,
> > > > 
> > > > The accessability provided by NAPT (Network Address Port Translator)
> > > > is not any less than the accessibility provided by a host with a 
> > > > single address. 
> > > > 
> > > > Further, Bidirectional-NAT does not preclude inbound connections.
> > > > It simply does address multiplexing - optimal use of limited
> > > > addresses available.
> > > > 
> > > > I suggest you take a look at <draft-ietf-nat-terminology-03.txt>
> > > > prior to spreading misinformation. 
> > > > 
> > > > cheers,
> > > > suresh
> > > > 
> > > > > 
> > > > > And just to make matters worse, I could not have anyone connect
> > directly to me
> > > > > thanks to NAT (i.e. ftp, SIP, etc).
> > > > > 
> > > > > PatC
> > > > > 
> > > > > > > > By the way, there are certain markets where NAT is a
> > requirement (such as
> > > > > > > > running IP to the guest rooms in hotels)
> > > > > > 
> > > > > > Until the hotels get more customers like Pat, who say that...
> > > > > > 
> > > > > > > hmm... so I HAVE to trust my hotel? What kind of customers are
> > they looking
> > > > > > > for? If they are looking for the commuter, then NAT is a bad
> > thing since I
> > > > > > > will want to encrypt my data back to my corporate network.
> > > > > > 
> > > > > > And by then they'll be looking for another alternative.
> > > > > > 
> > > > > > > > and IPSec is also extremely high profile.   It would help
> > everyone out if
> > > > > > > > there was a built-in method to scale arbitarily
> > > > > > > > large for address translated IPSec connections - just with
> > ESP, I don't
> > > > > > > > think that AH is as important to these users.
> > > > > > 
> > > > > > And that alternative is IPv6.  ESP works just fine over that.
> > > > > > 
> > > > > > Dan
> > > > > 
> > > > > 
> > > > > 
> > > > 
> > > 
> > > 
> > 
> > -- 
> >        Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
> >        Member, MIT Student Information Processing Board  (SIPB)
> >        URL: http://web.mit.edu/warlord/      PP-ASEL      N1NWH
> >        warlord@MIT.EDU                        PGP key available
> > 

-- 
       Derek Atkins, SB '93 MIT EE, SM '95 MIT Media Laboratory
       Member, MIT Student Information Processing Board  (SIPB)
       URL: http://web.mit.edu/warlord/      PP-ASEL      N1NWH
       warlord@MIT.EDU                        PGP key available


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