Operating a LANCOM R&S®Unified Firewall in transparent bridge mode

Description:

In some scenarios, it may be necessary to observe the data traffic on a network before operating the Unified Firewall. This can be achieved by using a transparent bridge.

This article describes how to operate a LANCOM R&S®Unified Firewall in bridge mode.

Requirements:

• LANCOM R&S®Unified Firewall with LCOS FX as of version 10.3
• Basic or full license (full license required for UTM functions)
• Configured and functional network including Internet access on the (LANCOM) router
• Web browser for configuring the Unified Firewall.
  
  The following browsers are supported:
  • Google Chrome
  • Chromium
  • Mozilla Firefox

Scenario:

• The router supports the IP network 192. 168.1.0/24 and operates with the IP address 192.168.1.254. 
• The Unified Firewall is connected to the router via the interface eth1. The Unified Firewall is assigned the IP address 192. 168.1.1 on this interface.
• The Unified Firewall is connected to the local network via the interface eth2. The Unified Firewall is assigned to the network 192. 168.1.0/24 on this interface.

Procedure:

1) Setting up bridge mode on the Unified Firewall:

1.1) In your browser, open the configuration for the United Firewall and switch to the menu item Network → Connections → DNS Settings.

1.2) Modify the following parameters and then click Save:

• Acquire DNS server: Remove the checkmark so that you can specify a DNS server.
• 1st name server : Specify the IP address of a DNS server so that the Unified Firewall can perform name resolution (in this example the DNS server 8.8.8.8 ).

1.3) Switch to the menu Network → Connections → Network Connections and use the “trash can” icon to delete the two unused connections (in this example eth1 and eth2), which frees up two Ethernet ports for the operation as a bridge.

1.4) Navigate to the menu Network → Interfaces → Bridge Interfaces and click on the “+” icon to create a bridge.

1.5) Under Ports, add the Ethernet ports freed up in step 1.3 (in this example eth1 and eth2) and click on Create.

1.6) Change to the menu Network → Connections → Network Connections and click on the “+” icon to create a new connection.

1.7) Enter the following parameters:

• Name: Enter a descriptive name.
• Interface: From the drop-down menu, select the bridge interface (in this case br0) created in step 1.5.
• IP Addresses: Enter a free IP address from the router's network in CIDR format and add it using the “+” icon (in this example 168.1.1/24).

1.8) Switch to the tab WAN, adjust the following parameters and click Create:

• Set a checkmark next to Set default gateway.
• Under Default gateway, enter the IP address of the router (in this example 192.168.1.254).

1.9) Click the icon Click to generate an Internet object.

1.10) Modify the following parameters and then click Create:

• Object Name: Enter a descriptive name.
• Connections : In the drop-down menu, select the connection created in steps 1.7 and 1.8  and add it using the “+” icon.

1.11) Click the icon Click to create a network.

1.12) Modify the following parameters and then click Create:

• Name: Enter a descriptive name.
• Interface: Select the bridge interface br0 created in step 1.5.
• Network IP : Enter the network address of the router in CIDR format (in this example 192.168.1.0/24 ).

1.13) Finally, implement the changes on the United Firewall by clicking Activate.

2) Logging and analyzing the data traffic:

There are various options for logging and then analyzing the data packets. The following describes two different approaches, “Deny All” and “Allow All”). 

The following UTM functions can also be configured:

• Setting up application management
• Setting up Intruder Detection/Intruder Prevention (IDS / IPS) from step 2.

2.1) Deny All:

Since the factory default is to discard all packets (Deny All strategy), there is no need to create a separate firewall rule.

This mode is only suitable for checking the traffic for a short period of time because no communication is possible.

2.1.1) Navigate to the menu Monitoring & Statistics → Settings.

2.1.2) For each of the following options, select Save Raw Data locally so that the blocked packets are logged in detail. Then click on Save.

• Blocked Inbound Traffic
• Blocked Forwarded Traffic
• IDPS Alert (only when using the IDS/IPS function)

2.1.3) Navigate to the menu Monitoring & Statistics → Logs → Alert Log. 

2.1.4) In the field More filters, select the filter Category: Connection blocked so that the Unified Firewall displays the blocked packets.

2.2) Allow All:

In order to allow all packets, an object must be created that applies to all ports and protocols. This can then be used in a firewall rule.

This mode can be used for a longer period of time because full communication is allowed.

2.2.1) Change to the menu Desktop → Services → User-defined Services and click on the “+” icon to create a new user-defined service.

2.2.2) Under Name enter a descriptive name and click on the “+” icon under Ports and Protocols to select the port and protocol.

2.2.3) Set the ports from 1 - 65535 and set a checkmark for TCP and UDP. Then click on OK.

2.2.4) Additionally add the protocols ICMP,  AH, ESP and GRE. 

2.2.5) Click Create to create the user-defined service.

2.2.6) Click the network object on the desktop created in step 1.12 (in this example LAN), select the connection tool and click the Internet object created in step 1.10 (in this example WAN-Bridge).  

2.2.7) Add the user-defined service created in steps 2.2.2 - 2.2.5.

2.2.8) Under Action, click three times on the green arrow so that it becomes a two-way arrow, meaning communication is allowed in both directions.

2.2.9) Under Options, click on NAT to adjust further settings.

2.2.10) Set the NAT/Masquerading to Off so that the data traffic is transmitted transparently.

2.2.11) Then click Create.

2.2.12) Finally, implement the changes by clicking Activate.

2.2.13) Navigate to the menu Monitoring & Statistics → Settings.

2.2.14) Under Web content allowed, select the option Save raw data locally to log the permitted data traffic in detail.

2.2.15) Navigate to the menu Monitoring & Statistics → Logs → Alert Log. 

2.2.16) In the field More filters, select the filter Category: Connection finished so that the Unified Firewall displays the transferred packets.