![](/images/new-backgrounds/1195574/195574203x1.webp)
Scenario 2: The 3-Leg Perimeter Configuration
The
Table 2:
Firewall Policy |
| Description |
|
Block all |
| Block all network access through ISA Server. |
|
|
| This option does not create any access rules other than the default |
|
|
| rule which blocks all access. |
|
|
| Use this option when you want to define firewall policy on your |
|
|
| own. |
|
|
|
|
|
Block Internet access, |
| Block all network access through ISA Server, except for access to |
|
allow access to |
| network services, such as DNS on the perimeter network. Use this |
|
network services on |
| option when you want to define the firewall policy on your own. |
|
the perimeter network |
| The following access rules will be created: |
|
|
|
| |
|
| 1. Allow DNS traffic from Internal Network and VPN Clients |
|
|
| Network to Perimeter Network |
|
|
|
|
|
Block Internet access, |
| Prevent all network access through the firewall except for network |
|
allow access to ISP |
| services such as DNS. This option is useful when your Internet |
|
network services |
| Service Provider (ISP) provides network services. |
|
|
| Use this option when you want to define the firewall policy on your |
|
|
| own. |
|
|
| The following rules will be created: |
|
|
| 1. Allow DNS from Internal Network, VPN Clients Network and |
|
|
| Perimeter Network to External Network (Internet) |
|
|
|
|
|
Allow limited Web |
| Allow limited Web access using HTTP, HTTPS, FTP only and allow |
|
access, allow access |
| access to network services such as DNS on the perimeter network. |
|
to network services |
| All other network access is blocked. |
|
on perimeter network |
| This option is useful when network infrastructure services are |
|
|
|
| |
|
| available on the perimeter network. |
|
|
| The following access rules will be created: |
|
|
| 1. Allow HTTP, HTTPS, FTP from Internal Network and VPN |
|
|
| Clients Network to Perimeter Network and External Network |
|
|
| (Internet) |
|
|
| 2. Allow DNS traffic from Internal Network and VPN Clients |
|
|
| Network to Perimeter Network |
|
|
| 3. Allow all protocols from VPN Clients Network to Internal |
|
|
| Network |
|
|
|
|
|
Allow limited Web |
| Allow limited Internet access and allow access to network services |
|
access and access to |
| such as DNS provided by your Internet Service Provider (ISP). All |
|
ISP network services |
| other network access is blocked. |
|
|
|
|
|
ISA Server 2004 Configuration Guide | 100 |