Newsgroup: it.comp.os.win.win2000
Titolo: 70-216: domanda su filtri in un una VPN. Qualcuno mi sa rispondere?

Ragazzi datemi una mano...
Mi sono imbatturo nella domanda sequente:
You are the administrator of your company's network, which consists of a 
single Windows 2000 domain. The network has a persistent connection to 
the internet. The relevant portion of its configuration is shown in the 
exhibit.
  _              _
| |domain      | |domain
| |controller  | |controller
|_|            |_|                                        / mobile user
                         _          _                     /
                        | |        | |                   /
                        | |--------| |-------- internet  --- mobile user
      intranet  firewall|_|        |_|                   \
                                   VPN1                   \
                                                           \ mobile user
  _              _
| |application | |file
| |server      | |server
|_|            |_|
Your company employs mobile salespeople who use portable computers, 
which run either Windows 98 or Windows 2000 Professional. To enable 
these users to access internal resources, you place a virtual private
network server named VPN1 outside your firewall. VPN1 is a stand-alone 
Windows 2000 Server computer running routing and remote access. The 
firewall performs network address translation, and it is configured to 
allow inbound access from VPN1only.
You need to use the most secure VPN connection possible for each 
connection. You configure appropriate VPN ports on VPN1.
VPN1 must now be configured to allow only appropriate traffic through 
the firewall on the internal interface. Which output and input filters 
should you configure for the internal network adapter?
SELECT AND PLACE:
output filters
|-----------|  -----------------------------   ------------------------
|           | |destination:firewall external| |source:firewall external|
|-----------| |address, tcp port 1723       | |address, tcp port 1723  |
|           |  -----------------------------   ------------------------
|-----------|  -----------------------------   ------------------------
|           | |destination:firewall external| |source:firewall external|
|-----------| |address, tcp port 500        | |address, tcp port 500   |
                -----------------------------   ------------------------
input filters
|-----------|  -----------------------------   ------------------------
|           | |destination:firewall external| |source:firewall external|
|-----------| |address, tcp port 1701       | |address, tcp port 1701  |
|           |  -----------------------------   ------------------------
|-----------|  -----------------------------   ------------------------
|           | |destination:firewall external| |source:firewall external|
|-----------| |address, ip protocol ID47    | |address,ip protocolID47 |
                -----------------------------   ------------------------
                -----------------------------   ------------------------
               |destination:firewall external| |source:firewall external|
               |address, ip protocol ID50    | |address,ip protocolID50 |
                -----------------------------   ------------------------
La mia risposta (sbagliata) è stata:
Output filter: destination firewall external address, tcp port 1723
                destination firewall external address, ip protocol ID47
Input  filter: source firewall external address, tcp port 1723
                source firewall external address, ip protocol ID47
Quella corretta invece è:
Output filter: source firewall external address, tcp port 1723
                source firewall external address, ip protocol ID47
Input  filter: destination firewall external address, tcp port 1723
                destination firewall external address, ip protocol ID47
Perché?

 Perché?
Riflettici e scopri il perchè
Output = uscita
Input = entrata
Source=Rete/IP di partenza
Destination= Rete/IP di Arrivo
 Saluti.