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BDPU Filter: Here’s a Quick Guide to BDPU Filtering

BDPU Filter: Here’s a Quick Guide to BDPU Filtering

Spanning Tree Protocol (STP) is a networking protocol that prevents loops in a network by selectively blocking certain links.

One of the critical elements of STP is Bridge Protocol Data Units (BPDUs), which are special messages exchanged between switches to determine the topology of the network.

BPDU filters are a useful tool that can be used to prevent BPDUs from reaching certain parts of the network.

In this article, we will provide a detailed explanation of BPDU filters, how they work, and the advantages and disadvantages of using them in a network environment.

I strongly recommend checking the Layer 2 Course for those who want to learn more about this topic.

What Are BPDU Filters and How Do They Work?

BPDU filters are used to prevent the transmission or reception of Bridge Protocol Data Units (BPDUs) on a specific switch port. BPDUs are special messages exchanged between switches in a network running the Spanning Tree Protocol (STP). 

More specifically, BPDU filters evaluate incoming data as it travels across a switch port, then filter out any bridge protocol data unit (BPDU) which has been designated for removal. When properly configured and maintained, these filters can minimize switch reconfiguration time so that performance is not affected by frequent topology changes. Additionally, this technique is invaluable in protecting the switch from malicious outside influences, as it prevents malicious actors from changing the topology without being detected. All in all, BPDU filters provide an effective tool for preserving network integrity, security, and performance.

In summary, BPDU filters are used to prevent the transmission or reception of BPDUs on specific switch ports. They are useful for improving network security and stability. Still, they should be carefully planned and deployed to avoid isolating parts of the network or disrupting the normal operation of STP.

BDPU Guard vs. BPDU Filter

BPDU filter and BPDU guard are two types of features that can be configured on a switch port to prevent the transmission or reception of Bridge Protocol Data Units (BPDUs).

Here are the main differences between the BPDU filter and the BPDU guard:

  1. Purpose: BPDU filter is used to prevent the transmission of BPDUs on a switch port, while the BPDU guard is used to prevent the reception of BPDUs on a switch port.
  2. Operation: BPDU filter will block all BPDUs from being transmitted out of a switch port, while the BPDU guard will shut down the port if a BPDU is received on it.
  3. Use cases: BPDU filter is typically used to isolate parts of the network from the rest of the network and prevent the formation of loops, while the BPDU guard is used to protect the root bridge (the switch at the top of the STP hierarchy) from unauthorized changes or to prevent unauthorized switches from being added to the network.

In summary, the BPDU filter and BPDU guard are two different features that serve different purposes in a network running STP. A BPDU filter is used to prevent the transmission of BPDUs on a switch port, while a BPDU guard is used to prevent the reception of BPDUs on a switch port.

Advantages and Disadvantages of Using BPDU Filtering

There are several advantages and disadvantages of using BPDU filtering in a network environment:

Advantages

  1. Improved security: BPDU filters can be used to prevent unauthorized switches from being added to the network, which can help improve network security.
  2. Increased stability: By preventing the transmission or reception of BPDUs on specific switch ports, BPDU filters can help prevent loops in the network and improve overall stability.
  3. Enhanced performance: By isolating specific parts of the network from the rest of the network, BPDU filters can improve the performance of critical network services.

Disadvantages

  1. Risk of network isolation: If BPDU filters are not carefully planned and deployed, they can accidentally isolate parts of the network from the rest of the network, disrupting network connectivity.
  2. Potential impact on STP: Spanning Tree BPDU filters can disrupt the normal operation of STP, potentially leading to network outages or other issues.
  3. The complexity of deployment: Deploying BPDU filters requires careful planning and configuration, which can be complex and time-consuming.

Before implementing, it is crucial to weigh the pros and cons of using BPDU filters in a given network environment.

How to Configure BDPU Filtering on Cisco?

To enable BPDU filtering on a switch, you can use the following steps:

  1. Log in to the switch using your administrative credentials.
  2. Enter global configuration mode by typing the following command:

switch# configure terminal 

  1. Navigate to the interface you want to configure by typing the following command:

switch(config)# interface [interface-name] 

Replace [interface-name] with the name of the interface you want to configure, such as FastEthernet 0/1.

  1. Enable BPDU filtering on the interface by typing the following command:

switch(config-if)# spanning-tree bpdufilter enable 

This will prevent the transmission of BPDUs on the specified interface.

  1. Exit interface configuration mode by typing the following command:

switch(config-if)# exit 

  1. Save the configuration changes by typing the following command:

switch(config)# exit switch# write memory 

That's it! You have successfully enabled BPDU filtering on the specified interface. You can verify the configuration by using the show running-config command. To disable the BPDU filtering on your Cisco device, you can simply use the no spanning-tree portfast bpdufilter default command.

Summary

In summary, BPDU filters are useful for improving network security and stability by preventing the transmission or reception of Bridge Protocol Data Units (BPDUs) on specific switch ports. They are typically used in conjunction with other Spanning Tree Protocol (STP) features and should be carefully planned and deployed to avoid isolating parts of the network or disrupting the normal operation of STP. By following best practices and thoroughly considering their deployment, BPDU filters can provide significant benefits regarding network security and performance. You can get further information on STP and its features, such as BPDU filtering and BPDU guard, at orhanergun.net

Author:

Stanley Arvey
Stanley Arvey I am a certified network engineer with over 10 years of experience in the field. I have a deep understanding of networking and IT security, and I am always looking for new challenges.

Stanley Arvey, the dynamic world of Information Technology's intricacies and nuances, has been navigating for over a decade. With a keen eye for detail and a passion for simplifying complex tech concepts, Stanley has become a sought-after voice in the IT blogging community. Through his contributions to OrhanErgun.net, he provides insights, analyses, and thought leadership that keep readers both informed and engaged.