[WEBINAR] Bulletproof: How Today's Business Leaders Stay on Top

Transparent Bridge

Definition - What does Transparent Bridge mean?

A transparent bridge is a common type of bridge that observes incoming network traffic to identify media access control (MAC) addresses. These bridges operate in a way that is transparent to all the network's connected hosts.A transparent bridge records MAC addresses in a table that is much like a routing table and evaluates that information whenever a packet is routed toward its location. A transparent bridge may also combine several different bridges to better inspect incoming traffic. Transparent bridges are implemented primarily in Ethernet networks.

Techopedia explains Transparent Bridge

Transparent bridges maintain a list of MAC addresses, as do routers, based on all the received frames' source data-link MAC addresses. These tables are used for address look-up while forwarding a frame.

Transparent bridges save and maintain the source-route addresses of incoming frames by listening to all the connected bridges and hosts. They use a transparent bridging algorithm to a accomplish this. The algorithm has five parts:

  • Learning
  • Flooding
  • Filtering
  • Forwarding
  • Avoiding loops

For example, consider three hosts, A, B and C, and a bridge with three ports. Host A is connected to Bridge Port 1, Host B is connected to Bridge Port 2 and Host C is connected to Bridge Port 3. Host A sends a frame to the bridge that is addressed to Host B. The bridge checks the frame's source address and creates an address and port number entry for Host A in its forwarding table. The bridge then examines the frame's destination address, but does not find it in its forwarding table. As a result, the bridge sends the frame to all the other ports (2 and 3). This is called flooding. The frame is then received by Host B and Host C, which also check the destination address. Host B recognizes a destination address match and sends a response to Host A.

On the return path, the bridge adds an address and port number entry for Host B to its forwarding table. The bridge already has Host A's address in its forwarding table so it forwards the response only to Port 1. In this way, none of the Port 3 hosts are burdened with response requirements. Through this process, two-way communication between Host A and Host B is facilitated without the need for further flooding.

Share this:

Connect with us

Email Newsletter

Join thousands of others with our weekly newsletter

The 4th Era of IT Infrastructure: Superconverged Systems
The 4th Era of IT Infrastructure: Superconverged Systems:
Learn the benefits and limitations of the 3 generations of IT infrastructure – siloed, converged and hyperconverged – and discover how the 4th...
Approaches and Benefits of Network Virtualization
Approaches and Benefits of Network Virtualization:
Businesses today aspire to achieve a software-defined datacenter (SDDC) to enhance business agility and reduce operational complexity. However, the...
Free E-Book: Public Cloud Guide
Free E-Book: Public Cloud Guide:
This white paper is for leaders of Operations, Engineering, or Infrastructure teams who are creating or executing an IT roadmap.
Free Tool: Virtual Health Monitor
Free Tool: Virtual Health Monitor:
Virtual Health Monitor is a free virtualization monitoring and reporting tool for VMware, Hyper-V, RHEV, and XenServer environments.
Free 30 Day Trial – Turbonomic
Free 30 Day Trial – Turbonomic:
Turbonomic delivers an autonomic platform where virtual and cloud environments self-manage in real-time to assure application performance.