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Manual Chapter: Deploying the BIG-IP Network Firewall in Firewall Mode
Manual Chapter
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Deploying the BIG-IP Network Firewall in Firewall Mode

About Firewall mode in the Network Firewall

The BIG-IP® Advanced Firewall Manager™ (AFM™) provides policy-based access control to and from address and port pairs, inside and outside of your network. In this scenario, the network firewall is configured in Firewall mode, a default deny configuration, in which all traffic is blocked through the firewall, and any traffic you want to allow must be explicitly specified.

To understand this firewall scenario, imagine that your prerequisite system load-balances all traffic from the Internet to several internal servers. The internal servers are:

Device and location IP address Traffic type
Server on DMZ network 70.168.15.104 FTP
Server on internal network 10.10.1.10 HTTP, HTTPS
Server on internal network 10.10.1.11 HTTP, HTTPS

In order for traffic from the internal application virtual server to reach the external network virtual server, you must create a VLAN and enable both internal and external virtual servers on it. In this scenario, these VLANs are specified:

VLAN Configuration
net_ext Enabled on 70.168.15.0/24, 192.168.15.101
net_int Includes pool members 10.10.1.10, 10.10.1.11

In addition, in this firewall configuration, there are three external networks that must be firewalled:

Network Policy
60.63.10.0/24 Allow all access
85.34.12.0/24 Deny all access
48.64.32.0/24 Allow FTP, deny HTTP and HTTPS
To set up this scenario, you configure addresses, ports, and firewall rules specific to these networks, ports, and addresses.

Firewall configuration scenario

Network firewall Firewall mode example

Configuring the Network Firewall to drop traffic that is not specifically allowed

You can configure the BIG-IP® Network Firewall to deny all traffic not explicitly allowed. In Advanced Firewall Manager™ this is called Firewall mode, and this is also referred to as a default deny policy. Firewall mode applies a default deny policy to all self IPs and virtual servers.
  1. On the Main tab, click Security > Options > Network Firewall .
    The Firewall Options screen opens.
  2. From the Virtual Server & Self IP Contexts list, select the default action Drop for the self IP and virtual server contexts.
  3. Click Update.
    The default virtual server and self IP firewall context is changed.
If you are using ConfigSync to synchronize two or more devices, and you set the default action to Drop or Reject, you must apply the built-in firewall rules _sys_self_allow_defaults or _sys_self_allow_management to the specific self IPs that are used to support those services. To do this, add a new rule with the Self IP context, select the self IP, and select the Rule List rule type. Finally, select the preconfigured rules from the list of rule lists.

Creating a VLAN for the network firewall

Create a VLAN with tagged interfaces, so that each of the specified interfaces can process traffic destined for that VLAN.
  1. On the Main tab, click Network > VLANs .
    The VLAN List screen opens.
  2. Click Create.
    The New VLAN screen opens.
  3. In the Name field, type a unique name for the VLAN.
    For purposes of this implementation, name the VLAN net_ext.
  4. For the Interfaces setting, click an interface number or trunk name from the Available list, and use the Move button to add the selected interface or trunk to the Tagged list. Repeat this step as necessary.
    You can use the same interface for other VLANs later, if you always assign the interface as a tagged interface.
  5. If you want the system to verify that the return route to an initial packet is the same VLAN from which the packet originated, select the Source Check check box.
  6. From the Configuration list, select Advanced.
  7. In the MTU field, retain the default number of bytes (1500).
  8. If you want to base redundant-system failover on VLAN-related events, select the Fail-safe box.
  9. From the Auto Last Hop list, select a value.
  10. From the CMP Hash list, select a value.
  11. To enable the DAG Round Robin setting, select the check box.
  12. Click Finished.
    The screen refreshes, and displays the new VLAN from the list.
The new VLAN appears in the VLAN list.
Enable the new VLAN on both the network virtual server and the application virtual server.

Configuring an LTM virtual server with a VLAN for Network Firewall

For this implementation, at least two virtual servers and one at least one VLAN are assumed, though your configuration might be different.
You enable two virtual servers on the same VLAN to allow traffic from hosts on one virtual server to reach or pass through the other. In the Network Firewall, if you are using multiple virtual servers to allow or deny traffic to and from specific hosts behind different virtual servers, you must enable those virtual servers on the same VLAN.
Tip: By default, the virtual server is set to share traffic on All VLANs and Tunnels. This configuration will work for your VLANs, but in the firewall context specifying or limiting VLANs that can share traffic provides greater security.
  1. On the Main tab, click Local Traffic > Virtual Servers .
    The Virtual Server List screen opens.
  2. Click the name of the virtual server you want to modify.
  3. From the VLAN and Tunnel Traffic list, select Enabled on. Then, for the VLANs and Tunnels setting, move the VLAN or VLANs on which you want to allow the virtual servers to share traffic from the Available list to the Selected list.
  4. Click Update to save the changes.
  5. Repeat this task for all virtual servers that must share traffic over the VLAN.
The virtual servers on which you enabled the same VLAN can now pass traffic.

Creating an address list

Use this procedure to specify the address list to apply to allow access to specific source addresses.
  1. On the Main tab, click Security > Network Firewall > Address Lists .
    The Address Lists screen opens.
  2. Click Create to create a new address list.
  3. In the name field, type ADDR_LIST1.
  4. In the Addresses area, add the following addresses: 48.63.32.0/24 and 60.63.10.0/24. Click Add after you type each address.
  5. Click Finished.
    The list screen and the new item are displayed.

Allowing access from networks on an address list with a firewall rule

The firewall rules in this example apply in the virtual server context. For purposes of this example, the external network-facing virtual server is named ex_VS and has an IP address of 70.168.15.0/24.
Create a firewall rule that allows traffic from the networks on ADDR_LIST1 to the DMZ network, which includes an FTP server that is publicly addressed, and two internal servers on a second virtual server.
  1. On the Main tab, click Security > Network Firewall > Active Rules .
    The Active Rules screen opens.
  2. In the Rules area, click Add to add a firewall rule to the list.
  3. From the Context list, select Virtual Server, and then select the external virtual server (in the example, ex_VS).
  4. In the Name field, type allow_addr_list.
  5. From the Type list, select Rule.
  6. From the State list, select Enabled.
  7. From the Protocol list, select Any.
  8. In the Source area, from the Address list, select Specify, and click Address List.
  9. From the list, select /Common/ADDR_LIST1, then click Add to add ADDR_LIST1 to the list.
  10. Leave the Destination area configured with the default Any / Any settings.
  11. From the Action list, select Accept.
    This allows packets from any source on the list to the any destination and port on any protocol on the DMZ network.
  12. From the Logging list, enable or disable logging for the firewall rule.
  13. Click Finished.
    The list screen and the new item are displayed.
A new firewall rule is created, and appears in the firewall rule list.

Allowing access from a network to a virtual server with a firewall rule

The firewall rules in this example apply in the virtual server context. For purposes of this example, the application virtual server is behind the network virtual server with an IP address of 192.168.15.101 and configured for traffic on ports 80 and 443.
Use this procedure to create a firewall rule that allows traffic from a specific external network to the HTTP and HTTPS servers behind an application virtual server.
  1. On the Main tab, click Security > Network Firewall > Active Rules .
    The Active Rules screen opens.
  2. In the Rules area, click Add to add a firewall rule to the list.
  3. In the Context field, select Virtual Server, and select the application virtual server (in the example, 192.168.15.101.
  4. In the Name field, type allow_app_vs.
  5. From the Type list, select Rule.
  6. From the State list, select Enabled.
  7. From the Protocol list, select Any.
  8. In the Source area, from the Address list, select Specify.
  9. In the address field, type 60.63.10.0/24, then click the Add button.
  10. Leave the Destination area configured with the default Any / Any settings.
  11. From the Action list, select Accept.
    This allows packets from the specified source to any destination and port on any protocol on the internal virtual server. You could specify HTTP and HTTPS protocols, and the internal server addresses, but since these are the only addresses and protocols behind the virtual server, that level of granularity is not necessary.
  12. From the Logging list, enable or disable logging for the firewall rule.
  13. Click Finished.
    The list screen and the new item are displayed.
A new firewall rule is created, and appears in the firewall rule list.
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