Spanning Tree Bpdu Support; Advanced Settings For Transparent Mode; An Example Bpdu Relaying Scenario - D-Link DFL-1660 User Manual

4.7.4. Spanning Tree BPDU Support

• Destination Interface: dmz
• Source Network: all-nets
• Destination Network: wan_ip
9. Click OK
4.7.4. Spanning Tree BPDU Support
NetDefendOS includes support for relaying the Bridge Protocol Data Units (BPDUs) across the
NetDefend Firewall. BPDU frames carry Spanning Tree Protocol (STP) messages between layer 2
switches in a network. STP allows the switches to understand the network topology and avoid the
occurrences of loops in the switching of packets.
The diagram below illustrates a situation where BPDU messages would occur if the administrator
enables the switches to run the STP protocol. Two NetDefend Firewalls are deployed in transparent
mode between the two sides of the network. The switches on either side of the firewall need to
communicate and require NetDefendOS to relay switch BPDU messages in order that packets do not
loop between the firewalls.
Figure 4.16. An Example BPDU Relaying Scenario
Implementing BPDU Relaying
The NetDefendOS BDPU relaying implementation only carries STP messages. These STP messages
can be of three types:
• Normal Spanning Tree Protocol (STP)
• Rapid Spanning Tree Protocol (RSTP)
• Multiple Spanning Tree Protocol (MSTP)
• Cisco proprietary PVST+ Protocol (Per VLAN Spanning Tree Plus)
NetDefendOS checks the contents of BDPU messages to make sure the content type is supported. If
it is not, the frame is dropped.
Enabling/Disabling BPDU Relaying
BPDU relaying is disabled by default and can be controlled through the advanced setting Relay
Spanning-tree BPDUs. Logging of BPDU messages can also be controlled through this setting.
When enabled, all incoming STP, RSTP and MSTP BPDU messages are relayed to all transparent
interfaces in the same routing table, except the incoming interface.

4.7.5. Advanced Settings for Transparent Mode

CAM To L3 Cache Dest Learning
Enable this if the firewall should be able to learn the destination for hosts by combining destination
address information and information found in the CAM table.
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Chapter 4. Routing